Diesel fuel in oil

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Search this Thread Display Modes   09-02-2022, 10:56 PM   #1 Dwk

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Diesel fuel in oil

What are the causes for diesel fuel in engine oil? My friends Perkins T6.354 is getting fuel in the oil.They thought it was faulty injectors but after rebuilding the fuel is still present in the oil after test running. What other possibilities for fuel getting into oil should they investigate ?

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  09-02-2022, 11:58 PM   #2 STB

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What are the causes for diesel fuel in engine oil? My friends Perkins T6.354 is getting fuel in the oil.They thought it was faulty injectors but after rebuilding the fuel is still present in the oil after test running. What other possibilities for fuel getting into oil should they investigate ?

Most of the time on the 6.354 it is a bad mechanical lifter pump. When the membrane gets even a little perforated, a ton of fuel can get in the oil. This is a relatively fast, easy, inexpensive, very available fix.

Almost all of the rest of the time it is the injector pump, not the injectors. When the shaft seal (maybe there are two, I dont remember without looking) fails, tons of fuel can quickly get in to the oil. A rebuilder can check this on the bench, but will usually charge for a full rebuild if repair is needed.

The usual advice is to replace the lifter pump, change the oil and filter, and test again almost immediately, after just enough run time to get to temperature and everything mixed well, and then test again after a small several hours of use.

It is important to sample mmediately so there is a baseline to compare with the next sample (the one taken after some real use). Without that, one can easily be confused because not all the old oil, and with it the old contaminating fuel, gets changed during an oil change.

If the two samples show the same level of fuel dilution, that just means that the oil needs to be changed again until the old contamination is sufficiently diluted out (oil changes dont get all of the old oil out, and that engine can be particularly hard, depeneing upon how you go about it, given the shape of the pan). But if the 2nd sample is notably higher than the 1st sample, the problem is ongoing and the lifter didn't fix it, so attention should be turned to the injector pump.

After swapping the lifter, take a look at the membrane on the old one. A lot of times tou'll see the failure and, therefore, be confident you fixed it. If not, hang onto it as a spare, at least until you see what the oil samples suggest.

Obviously, even after you think you've fixed the problem, sample frequently for a bit to be sure. Some failures may only occur under load, when hot, episodcially, etc.

If you haven't done oil samples before, just get a pump and a kit from Amazon. They are both inexpensive. The one time use kit is usually ~$20 and includes the cost of the lab analysis. Just send it in. Drawing the sample is just warming up the engines a bit, then shutting down, threading a tube into the oil pan (without scraping up any sludge at the very bottom), and using the hand pump to draw a sample into the sample container. The kit usually comes with both the one-time-use tube and container (but check, because some only contain the container, which is a bummer for most).

Of course I have many questions...

How do you know there is fuel dilution? How much? And over how many hours of engine run time?

And, how is the engine running, otherwise? Is there a ton of white fuel smoke? A big slick on the water? Dirty underway? A ton of blowby?

And, how has the boat been used? Are those hours idling at the dock in short stints? Or underway largely at cruise?

A slow rate of dilution in a boat with a lot of blowby might just be an aging engine.

A slow raye of dilution in an engine running dirty could just be aging or badly needing maintenance (air filter if equipped, valve timing, fuel filters, etc).

An engine idling a lot, e.g. rarely used for real but often idled at the dock, can diluted a lot faster than an engine running at cruise because it spends more time cool.and running dirty.

In general, the slower the rate of dilution and the more obvious the other performance problems, the more likely it is to be age, maintance, or injector or injector pump performance.

The better the engine is running otherwise and the faster the rate of dilution, the more likely it is to be a seal, most commonly the lifter membrane or injector pump shaft seal.

Snce most don't notice really slow dilution or just dismiss it with the other signs of the engine's general condition, the problem is most commonly the lifter pump (membrane) followed by the injector pump (shaft seal).

On the 6.354 it is rarely the injectors. You'd see a huge slick on the water and tons of white smoke before enough would get in the oil that way to flag an oil sample or "make oil" within a normal interval. I'm talking more than the expected white smoke and small slick the turbos versions of that engine like to produce at the dock. The problem would have likely gotten fixed for other reasons before fouling the oil.Most of the time on the 6.354 it is a bad mechanical lifter pump. When the membrane gets even a little perforated, a ton of fuel can get in the oil. This is a relatively fast, easy, inexpensive, very available fix.Almost all of the rest of the time it is the injector pump, not the injectors. When the shaft seal (maybe there are two, I dont remember without looking) fails, tons of fuel can quickly get in to the oil. A rebuilder can check this on the bench, but will usually charge for a full rebuild if repair is needed.The usual advice is to replace the lifter pump, change the oil and filter, and test again almost immediately, after just enough run time to get to temperature and everything mixed well, and then test again after a small several hours of use.It is important to sample mmediately so there is a baseline to compare with the next sample (the one taken after some real use). Without that, one can easily be confused because not all the old oil, and with it the old contaminating fuel, gets changed during an oil change.If the two samples show the same level of fuel dilution, that just means that the oil needs to be changed again until the old contamination is sufficiently diluted out (oil changes dont get all of the old oil out, and that engine can be particularly hard, depeneing upon how you go about it, given the shape of the pan). But if the 2nd sample is notably higher than the 1st sample, the problem is ongoing and the lifter didn't fix it, so attention should be turned to the injector pump.After swapping the lifter, take a look at the membrane on the old one. A lot of times tou'll see the failure and, therefore, be confident you fixed it. If not, hang onto it as a spare, at least until you see what the oil samples suggest.Obviously, even after you think you've fixed the problem, sample frequently for a bit to be sure. Some failures may only occur under load, when hot, episodcially, etc.If you haven't done oil samples before, just get a pump and a kit from Amazon. They are both inexpensive. The one time use kit is usually ~$20 and includes the cost of the lab analysis. Just send it in. Drawing the sample is just warming up the engines a bit, then shutting down, threading a tube into the oil pan (without scraping up any sludge at the very bottom), and using the hand pump to draw a sample into the sample container. The kit usually comes with both the one-time-use tube and container (but check, because some only contain the container, which is a bummer for most).Of course I have many questions...How do you know there is fuel dilution? How much? And over how many hours of engine run time?And, how is the engine running, otherwise? Is there a ton of white fuel smoke? A big slick on the water? Dirty underway? A ton of blowby?And, how has the boat been used? Are those hours idling at the dock in short stints? Or underway largely at cruise?A slow rate of dilution in a boat with a lot of blowby might just be an aging engine.A slow raye of dilution in an engine running dirty could just be aging or badly needing maintenance (air filter if equipped, valve timing, fuel filters, etc).An engine idling a lot, e.g. rarely used for real but often idled at the dock, can diluted a lot faster than an engine running at cruise because it spends more time cool.and running dirty.In general, the slower the rate of dilution and the more obvious the other performance problems, the more likely it is to be age, maintance, or injector or injector pump performance.The better the engine is running otherwise and the faster the rate of dilution, the more likely it is to be a seal, most commonly the lifter membrane or injector pump shaft seal.Snce most don't notice really slow dilution or just dismiss it with the other signs of the engine's general condition, the problem is most commonly the lifter pump (membrane) followed by the injector pump (shaft seal).

  09-03-2022, 07:34 AM   #3 Dwk

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STB,thanks for the detailed response. The lift pump has been changed so now it’s on to the injection pump for a rebuild. As you mentioned the oil seems to get diluted quickly ,another sigh pointing to the injector pump seals.

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  09-03-2022, 09:43 AM   #4 STB

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If you haven't done an oil sample....they are really easy and you'll have the results back in a few days:

Oil Analysis Premier Sample Pump by Under My Hood - Including Live Port and Storage Case

WIX Filters - 24078 Oil Analysis Kit, Pack of 1

I'm still curious about how much fuel over how many hours and how we know? And, how the engine is performing otherwise, at startup, at the slip, and at cruise, including its smoke signals?If you haven't done an oil sample....they are really easy and you'll have the results back in a few days:Oil Analysis Premier Sample Pump by Under My Hood - Including Live Port and Storage Case https://a.co/d/92appZf WIX Filters - 24078 Oil Analysis Kit, Pack of 1 https://a.co/d/0WyxWK7

  09-03-2022, 09:46 AM   #5 STB

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Dwk

Originally Posted by

STB,thanks for the detailed response. The lift pump has been changed so now it’s on to the injection pump for a rebuild. As you mentioned the oil seems to get diluted quickly ,another sigh pointing to the injector pump seals.

Also, I don't know where you see in the world, but in Florida and California where I've boated, the local rebuilders have been willing to bench test before doing a full rebuild to confirm something like this.

  09-03-2022, 09:54 AM   #6 Dwk

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STB

Originally Posted by

If you haven't done an oil sample....they are really easy and you'll have the results back in a few days:

Oil Analysis Premier Sample Pump by Under My Hood - Including Live Port and Storage Case

WIX Filters - 24078 Oil Analysis Kit, Pack of 1

I'm still curious about how much fuel over how many hours and how we know? And, how the engine is performing otherwise, at startup, at the slip, and at cruise, including its smoke signals?If you haven't done an oil sample....they are really easy and you'll have the results back in a few days:Oil Analysis Premier Sample Pump by Under My Hood - Including Live Port and Storage Case https://a.co/d/92appZf WIX Filters - 24078 Oil Analysis Kit, Pack of 1 https://a.co/d/0WyxWK7

I can’t answer these questions but will ask the owner to chime in and post the findings.

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  09-03-2022, 10:04 AM   #7 STB

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I guess let me also write this, not knowing who has done the diagnosis or how, I'm also a little concerned that the problem could be something else like water or coolant in the oil.

Someone with experience would be very unlikely to confuse the two, significantly fuel contaminated oil looks and acts different when checked in a variety of ways (on the dipstick, visually, when heated, etc) than oil contaminated with a lot of water.

But, with modern oils that can emulsify a lot of water, it is surprisingly easy to confuse the two at a casual glance, at least for modest dilution.

An oil sample puts a number to it that is pretty unambiguous.

A couple of oil samples ago on my boat fuel started showing up in the oil on one engine. I disbelieved it, the lifter was seemingly working great, and the injector pump had recently been rebuilt. But the report was clear. I replaced the lifter and samples have been clean since. For the life of me I couldn't see the problem with the lifter when inspected post removal. In my mind, it was a big preventative maintenance win for oil sampling. It'd have been a while before I noticed, but for that report.

As an aside, once upon a time one of my kits must have gotten a little contamination from condensation, I think the tubing. I pulled my hair out trying to figure out how I had freshwater contamination (not coolant, not saltwater, not fuel). Not easily possible in a saltwater boat. Took a new sample before the boat had been run (significantly) again and the water was gone and never reappeared. I actually called the lab to ask if it could be at their end and the tech told me that they ran the sample twice because it was so weird, but it was what it was.

  09-03-2022, 11:53 AM   #8 catalinajack

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STB

Originally Posted by

I guess let me also write this, not knowing who has done the diagnosis or how, I'm also a little concerned that the problem could be something else like water or coolant in the oil.

Someone with experience would be very unlikely to confuse the two, significantly fuel contaminated oil looks and acts different when checked in a variety of ways (on the dipstick, visually, when heated, etc) than oil contaminated with a lot of water.

But, with modern oils that can emulsify a lot of water, it is surprisingly easy to confuse the two at a casual glance, at least for modest dilution.

An oil sample puts a number to it that is pretty unambiguous.

A couple of oil samples ago on my boat fuel started showing up in the oil on one engine. I disbelieved it, the lifter was seemingly working great, and the injector pump had recently been rebuilt. But the report was clear. I replaced the lifter and samples have been clean since. For the life of me I couldn't see the problem with the lifter when inspected post removal. In my mind, it was a big preventative maintenance win for oil sampling. It'd have been a while before I noticed, but for that report.

As an aside, once upon a time one of my kits must have gotten a little contamination from condensation, I think the tubing. I pulled my hair out trying to figure out how I had freshwater contamination (not coolant, not saltwater, not fuel). Not easily possible in a saltwater boat. Took a new sample before the boat had been run (significantly) again and the water was gone and never reappeared. I actually called the lab to ask if it could be at their end and the tech told me that they ran the sample twice because it was so weird, but it was what it was.

Rid yourself of the diaphram type on-engine lift pump and replace with an electric pump and you will never have diesel in your from from that source again.

  09-03-2022, 03:27 PM   #9 STB

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Rid yourself of the diaphram type on-engine lift pump and replace with an electric pump and you will never have diesel in your from from that source again.

Nah. My boat will run just fine, even without any intervention while single handing, if the alternators fail and the genset is off or wires chaffe and fuses blow, or there is a problem with a battery bank, etc. Personally, I'd like to keep it that way.

  09-03-2022, 11:18 PM   #10 Dwk

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“I'm still curious about how much fuel over how many hours and how we know? And, how the engine is performing otherwise, at startup, at the slip, and at cruise, including its smoke signals?

My understanding was there was nothing unusual at startup, fired quickly, exhaust was normal and ran smoothly until oil pressure dropped,alarms sounded and engine was shut down. After having the injectors rebuilt during sea trial for 20 minutes fuel was in oil. Thanks

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  09-04-2022, 12:52 AM   #11 STB

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My understanding was there was nothing unusual at startup, fired quickly, exhaust was normal and ran smoothly until oil pressure dropped,alarms sounded and engine was shut down. After having the injectors rebuilt during sea trial for 20 minutes fuel was in oil. Thanks

Dilution isn't going to cause anything sudden unless it is by a massively fast infusion. That doesn't sound like a leaky seal or stuck injector tip. Especially if no smoke problem was noted, if anyone was paying attention.

What I'm worried about when oil pressure changes fast are the piston rings, problems with which can also lead to dilution.

In consideratuon of that possibility, how much blow by is there now? How isnthe smoke now? I'd also really, really send an oil sample out to be tested to see what the metals are doing. If the pre-change pilcis available, I'd send one of those, too.

But, I am still having trouble building the complete picture in my head....a happy day cruising...typical start up, typical cruise...WHAM! Oil pressure tanks and the alarm sounds. Engine is shut down. So pil pressure dropped from ~40-50psi to less than 20psi within seconds? Do I have that right?or what is the story?

Then the injectors were rebuilt...and the engine by magic is running beautifully again, with normal oil pressure, except that fuel is found in the oil after the short cruise. Is that right? If not, what is the story?

I don't see the oil pressure problem solved by the injector rebuild, especially jf it was sudden. But, let's assume it was fixed by the rebuild, reseating of a ring, or magic.

Now our only concern is fuel in the oil? I ask again, how much is there, and how do we know? And how much was there before the sea trial, and how do we know?

Is it just a little bit, maybe left over from before the oil change? Or did it get a lot worse in the the few minutes of run time? How do we know? How much oil was "made"? Or is the oil also disappearing?

I've really got to understand the details of the situation better to be of more help. In particular, what happened and how we know.

Okay. This is starting to sound like a very different scenario is possible. A sudden drop in oil pressure is concerning, especially enough to set off a typical alarm. What was the oil pressure immediately before the drop? After?Dilution isn't going to cause anything sudden unless it is by a massively fast infusion. That doesn't sound like a leaky seal or stuck injector tip. Especially if no smoke problem was noted, if anyone was paying attention.What I'm worried about when oil pressure changes fast are the piston rings, problems with which can also lead to dilution.In consideratuon of that possibility, how much blow by is there now? How isnthe smoke now? I'd also really, really send an oil sample out to be tested to see what the metals are doing. If the pre-change pilcis available, I'd send one of those, too.But, I am still having trouble building the complete picture in my head....a happy day cruising...typical start up, typical cruise...WHAM! Oil pressure tanks and the alarm sounds. Engine is shut down. So pil pressure dropped from ~40-50psi to less than 20psi within seconds? Do I have that right?or what is the story?Then the injectors were rebuilt...and the engine by magic is running beautifully again, with normal oil pressure, except that fuel is found in the oil after the short cruise. Is that right? If not, what is the story?I don't see the oil pressure problem solved by the injector rebuild, especially jf it was sudden. But, let's assume it was fixed by the rebuild, reseating of a ring, or magic.Now our only concern is fuel in the oil? I ask again, how much is there, and how do we know? And how much was there before the sea trial, and how do we know?Is it just a little bit, maybe left over from before the oil change? Or did it get a lot worse in the the few minutes of run time? How do we know? How much oil was "made"? Or is the oil also disappearing?I've really got to understand the details of the situation better to be of more help. In particular, what happened and how we know.

  09-04-2022, 02:00 PM   #12 Txs218

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It was our boat. New to us this season. Drove it back from Solomon’s island Md to middle river Md no issues. My husband changed all fluids including oil filter etc as a preventative measure to a new to us boat since you don’t know when previous owner did. Ride from middle river to bodkin river a 2 hr cruise no issues. It sat all weekend at their club. After sitting there my husband checked fluids and levels seemed fine before we took off for return trip. No unusual smoke etc at start up. Then about 30-45 minutes into return trip oil pressure dropped like 20 then oil alarm went off. Putted home and no other issues after that. Let boat sit a day or so and my husband checked oil and it was a higher than normal level also lost its viscosity. So he changer oil to a different type of oil to see if that made a difference. He noticed when changing oil more oil coming out than he put in. Next trip was middle river across bay to rockhall. No issues again on way there. Boat sat for 2 nights at slip. Checked fluids again before leaving and oil a little high. 30 minutes into ride low pressure alarm went off again and we shut down engine and got towed back in. Mechanic pulled injector and they were dirty old and prob original so we had those rebuilt. Changed oil after. Took out for a little cruise last weekend 1.5 hrs to a bar sat a few hrs and back and then next day went to use boat and too much oil again. My husband took out an extra gallon or more than was supposed to be in there.

  09-04-2022, 02:47 PM   #13 STB

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It was our boat. New to us this season. Drove it back from Solomon’s island Md to middle river Md no issues. My husband changed all fluids including oil filter etc as a preventative measure to a new to us boat since you don’t know when previous owner did. Ride from middle river to bodkin river a 2 hr cruise no issues. It sat all weekend at their club. After sitting there my husband checked fluids and levels seemed fine before we took off for return trip. No unusual smoke etc at start up. Then about 30-45 minutes into return trip oil pressure dropped like 20 then oil alarm went off. Putted home and no other issues after that. Let boat sit a day or so and my husband checked oil and it was a higher than normal level also lost its viscosity. So he changer oil to a different type of oil to see if that made a difference. He noticed when changing oil more oil coming out than he put in. Next trip was middle river across bay to rockhall. No issues again on way there. Boat sat for 2 nights at slip. Checked fluids again before leaving and oil a little high. 30 minutes into ride low pressure alarm went off again and we shut down engine and got towed back in. Mechanic pulled injector and they were dirty old and prob original so we had those rebuilt. Changed oil after. Took out for a little cruise last weekend 1.5 hrs to a bar sat a few hrs and back and then next day went to use boat and too much oil again. My husband took out an extra gallon or more than was supposed to be in there.

With oil growing anywhere near that amount, oil certainly couldn't be confused with coolant or water. That would look super different. So that concern is out.

...For a baseline, how much was changed originally, before the problem started?

When you write that the oil pressure "dropped like 20", I'm not sure exactly what you mean. Changing over time from 60psi cold to 40psi hot isn't a problem. Suddenly changing behavior from 40psi at cruise to 20psi at cruise is much more concerning. Also note that older engines can see a big pressure drop off when quickly transitioning from a hot fast cruise to idle, it depends how hot it runs.

...what is your cruise tempoccurred?

...what was the temperature when the drop off occured?

...What was the initial cold start psi? What is it now? What was the psi at cruise before the problem? What is the psi at cruise now? When it dropped off, how quickly did that happen?

...How do the two engines compare in these respects?

...Have we verified the gauges with a mechanical gauge? They are inexpensive on Amazon or at Harbor Freight.

...you didn't report a pressure problem your last time out. Did it go away?

...how is the blow by on that engine? In other words, with it running, feel the airflow leaving the crank case breather tube and engibe oil dipstick. At the breather, focyou feel nothing, light puffs, big puffs, or more? Anything at the dopstick?

Normally when people notice this type of problem the oil gain is a pint, or maybe even a quart. It is, hey, wait, I usually need to top off....huh....that looks a tad higher now than when I left...that is backwards....a gallon so fast is a buf lot.

I'm really curious about blow by. If it is modest, the problem may be just a big failure in the injector pump. But, if it heavy, I'm thinking rings in which case you may want a mechanic to perform a leak down test.

Woah. An extra gallon? It all depends on the filter, the cooler, how the coolers is plumbed in, external equipment, etc, and can vary wildly, but those usually only take about 2 gallons in a typical marine install. I think the pan, itself, when properly full, holds something like 3.2qt. An exta gallon is ~50% extra?With oil growing anywhere near that amount, oil certainly couldn't be confused with coolant or water. That would look super different. So that concern is out....For a baseline, how much was changed originally, before the problem started?When you write that the oil pressure "dropped like 20", I'm not sure exactly what you mean. Changing over time from 60psi cold to 40psi hot isn't a problem. Suddenly changing behavior from 40psi at cruise to 20psi at cruise is much more concerning. Also note that older engines can see a big pressure drop off when quickly transitioning from a hot fast cruise to idle, it depends how hot it runs....what is your cruise tempoccurred?...what was the temperature when the drop off occured?...What was the initial cold start psi? What is it now? What was the psi at cruise before the problem? What is the psi at cruise now? When it dropped off, how quickly did that happen?...How do the two engines compare in these respects?...Have we verified the gauges with a mechanical gauge? They are inexpensive on Amazon or at Harbor Freight....you didn't report a pressure problem your last time out. Did it go away?...how is the blow by on that engine? In other words, with it running, feel the airflow leaving the crank case breather tube and engibe oil dipstick. At the breather, focyou feel nothing, light puffs, big puffs, or more? Anything at the dopstick?Normally when people notice this type of problem the oil gain is a pint, or maybe even a quart. It is, hey, wait, I usually need to top off....huh....that looks a tad higher now than when I left...that is backwards....a gallon so fast is a buf lot.I'm really curious about blow by. If it is modest, the problem may be just a big failure in the injector pump. But, if it heavy, I'm thinking rings in which case you may want a mechanic to perform a leak down test.

  09-04-2022, 03:50 PM   #14 STB

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Just in thinking through this...for that volume of fuel...there is another possibility.

Verify your fuel return path.

1) is the fuel return valve open?
2) is the return valve functioning properly?
3) is the hard return rail undamaged (and functioning properly)?
4) is the hose from the rail to the valve good and clear?
5) is the hose from the valve to the tank good and clear?
6) are any connections good and clear?
7) If you disconnect the hose from the valve to the tank, does fuel flow out of it while the engine is running, e.g. catch it in a 5 gallon bucket. If not back track.

The oil pressure situation continues to concern me w.r.t. a ring or internal engine problem.

But, if I discard that as a symptom not a cause or red herring for the moment, then my next guess is that the fuel return valve is closed or bad (or another problem with that path).

So...I think my present suggestions, in the order I'd try them, are (1) check for massively excessive blow by (fast, easy, and free), (2) check the fuel return path (free and easy to do), (3) have a shop check the injector pump (probably free, but some effort and running around, but a very likely cause if nothing earlier on this list is a problem), (4) replace the lifter pump again (occasionally I've replaced an old part with a new bad part and this part is cheap and easy), and then (5) get a mechanic to do a leak down test (expensive, pain, will find the deep problems you hope you dont have).

I'd really like to understand the blow by situation, which I haven't heard anything about, yet. It isnt completely diagnostic, but can really help separate minor from major in many cases).

Ditto for more clarity about the oil pressure and smoke (for smoke, during the runs where the fuel accumulated). Those engines may smoke a little cold at the slip, but should clean up underway.

I'm wrestling with how much and how fast the fuel showed up.

  09-04-2022, 04:57 PM   #15 Larry M

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We had a fuel dilution issue. The return from the injectors was the cause.

  09-04-2022, 09:00 PM   #16 Txs218

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Woah. An extra gallon? It all depends on the filter, the cooler, how the coolers is plumbed in, external equipment, etc, and can vary wildly, but those usually only take about 2 gallons in a typical marine install. I think the pan, itself, when properly full, holds something like 3.2qt. An exta gallon is ~50% extra?

With oil growing anywhere near that amount, oil certainly couldn't be confused with coolant or water. That would look super different. So that concern is out.

...For a baseline, how much was changed originally, before the problem started?

Roughly 11 to 12 quarts

When you write that the oil pressure "dropped like 20", I'm not sure exactly what you mean. Changing over time from 60psi cold to 40psi hot isn't a problem. Suddenly changing behavior from 40psi at cruise to 20psi at cruise is much more concerning. Also note that older engines can see a big pressure drop off when quickly transitioning from a hot fast cruise to idle, it depends how hot it runs.

...what is your cruise tempoccurred?

Cruise temp is between 195 and 200 F.

...what was the temperature when the drop off occured?

Normally at a cold start and then a fast idle of 1000 rpm the pressure is 60. When the issue occurs at fast idle and rpm of 1000 the pressure is between 20 and 40. The pressure of 20 to 40 is when I catch the issue at the dock. The first time the issue occurred the pressure started at 60 and dropped to 10 within 20 minutes.

...What was the initial cold start psi? 40-45 What is it now? 20-25 What was the psi at cruise before the problem? At cruise when the oil is fresh the pressure is 45 What is the psi at cruise now? Have not taken it out recently since I suspect it would drop from 45 to nothing rather quickly When it dropped off, how quickly did that happen? 20 to 30 minutes

...How do the two engines compare in these respects? Boat only has a single

...Have we verified the gauges with a mechanical gauge? They are inexpensive on Amazon or at Harbor Freight. Yes verified with mechanical gauge, dash gauge and mechanical gauge are the same.

...you didn't report a pressure problem your last time out. Did it go away?

The issues typically occur after running the boat and then letting it sit overnight. The oil level rises. I just drained 2 gallons to get the level back to full on the dipstick.

...how is the blow by on that engine? In other words, with it running, feel the airflow leaving the crank case breather tube and engibe oil dipstick. At the breather, focyou feel nothing, light puffs, big puffs, or more? Anything at the dopstick?

I have not done that.

Normally when people notice this type of problem the oil gain is a pint, or maybe even a quart. It is, hey, wait, I usually need to top off....huh....that looks a tad higher now than when I left...that is backwards....a gallon so fast is a buf lot.

I'm really curious about blow by. If it is modest, the problem may be just a big failure in the injector pump. But, if it heavy, I'm thinking rings in which case you may want a mechanic to perform a leak down test.

The lift pump was just changed and the injectors all redone. I notice the injection pump does have some diesel leaking from it. Also I tried to rotate the pump to correct the timing but it is already to the max to reduce unburned fuel.

  09-05-2022, 11:56 AM   #17 Txs218

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I removed the blow by hose and at idle there is a slight blow. I would say 1/3 of what you would need to blow out a birthday candle

start up oil pressure today was 20 and 35 when i increased idle to 1,000. Yesterday i removed about 2 gallons of excess oil. The dipstick today was between low and full lines. Luckily i think the oil is still thick enough that i can run these tests. If we were to take the boat out and under load from past experience the alarm would be going off in 15 minutes or so.

  09-05-2022, 12:04 PM   #18 KnotYet

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Txs218

Originally Posted by

I removed the blow by hose and at idle there is a slight blow. I would say 1/3 of what you would need to blow out a birthday candle

start up oil pressure today was 20 and 35 when i increased idle to 1,000. Yesterday i removed about 2 gallons of excess oil. The dipstick today was between low and full lines. Luckily i think the oil is still thick enough that i can run these tests. If we were to take the boat out and under load from past experience the alarm would be going off in 15 minutes or so.

fuel is a poor substitute for lubricating oil and any damage will be costly.
At this point I would be talking to an injection pump shop as well as
checking the bybass fuel volume as suggested by several above.

I wouldn't put any load on the engine with that much dilution. Dieselfuel is a poor substitute for lubricating oil and any damage will be costly.At this point I would be talking to an injection pump shop as well aschecking the bybass fuel volume as suggested by several above.

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  09-05-2022, 01:33 PM   #19 STB

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Okay. That blow by sounds fine. That test isn't definitive, but points somewhat away from a major internal engine problem by eliminating at least some such types of failures.

I think all I've got for you is to check the return path and injector pump, and maybe the lifter (again). Maybe the valve broke or was mispositioned while it was being adjusted to change fuel filters, or something. Or maybe something was dropped and damaged the return rail or a hose delaminated and blocked or something. My best guess based upon what I'm hearing is injector pump (back to that), but I think return path or lifter are still candidates.

That start up oil pressure is way too low. But, with that much fuel in the oil I can't figure if that points to a cause of the fuel dilution or is, itself, a symptom. It mostly depends upon the oil pressure release valve and age of the engine, but I'd expect 40psi-60psi at cold idle. Maybe 35psi. Less than that and something is aging or off. By the book the oil pressure should be 30-60psi at normal operating speed and temperature, but can be lower at hot idle.

But there is one thing I'm still not understanding. Or I think I am misunderstanding. Is it the case that the oil level rises a little bit during use, but a lot overnight? Or did I misunderstand that.

I'm having a really hard time understanding that, because there is very little pressure in the system when the engine is off. And any it bleeds off quickly if there is any leak because itnis driven by a very small excess volume. Maybe gravity if your fuel level is higher than the engine level. And, there isn't really a gallon worth of reservoir in the system anywhere.

If it is happening that way, I'd have to wildly guess it is gravity feeding from the tanks, pushing through the lifter into the engine, or pushing past the lifter into the injector pump and down through the shaft seals into the engine. It seems like that would take a heck of a lot of head pressure. But since the return is to the top of the tank, it couldn't be draining that way. As a temporary measure, I'd try closing the fuel valves overnight.

...there isn't an inline electric primer or lifter pump running overnight, is there?

...How much higher is your fuel level than engine block?

...and, most importantly, am I understanding correctly that the bulk of the problem is overnight? (That's weird).

And, yeah, as KnotYet says, I wouldn't run the engines more than necessary until you think you've fixed it. You're doing nothing but washing down the cylinders until then.

Keep us posted!

  09-05-2022, 01:36 PM   #20 Larry M

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Given your diluted diesel and overfilled oil sump, you could get into a runaway diesel situation. If that happens, you must kill the air source immediately or you’ll be replacing the engine.

 

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Fuel dilution of the engine oil is a problem that faces many modern combustion engines. Also known as “crankcase dilution” it is a process where fuel is leaked into engine oil when it travels towards the crankcase. It is a process that occurs roughly 8 times per 1000 rpm for each cylinder, and whilst it occurs in every engine, it is a factor that contributes a significant amount of wear to the engine. It is also one of the main reasons why periodic oil testing is performed for many engines, as it inevitable that every engine will experience it. In this article, we look at what the main causes of fuel dilution are and the issues that it can cause.

The Causes of Fuel Dilution in Engine Oil

There is not one cause of fuel dilution within engine oils and this is a reason why it is such a common occurrence within engines. However, the main cause is through a process called blow-by. This occurs because most seals are not perfect (nor are the cylinders perfectly rounded), or there is an opening through the cylinder crosshatches, and this causes the migration of fuel and exhaust gases into the areas where the oil is used. This often happens in the region between the piston rings and the cylinder bore.

Other factors include leaking of the fuel injectors, incomplete combustion of the fuel, low engine temperatures, long periods of idle time and frequent short-distance driving. Below, we look at some of the other factors and mechanisms that contribute to fuel dilution in engine oils.

Wet Stacking

Wet stacking occurs in engines which are cold, i.e. engines that have not yet reached their optimum operating temperature. Colder engines have a lower combustion efficiency than engines which are at the ideal operating temperature, and this causes the fuel to ignite further on in the compression stroke (because of the lower internal temperatures). This can also cause the fuel coming out of the injector to stick to the walls of the cylinder. Once the fuel is stuck to the sides, it will slowly enter the oil system by being scraped off by the piston rings and entering the crankcase.

Poor Maintenance

Fuel dilution within an oil system happens slowly. So, when some oil becomes contaminated with a small amount of fuel, the effects are very minimal and won’t affect the performance of the oil (or the engine in general). That is if it isn’t allowed to build up—that is when issues start to arise as large amounts of fuel dilution will affect the performance of the oil and the engine. Therefore, regular maintenance in the form of regular oil checks and changes can stop fuel dilution from presenting any adverse effects, but there can be catastrophic consequences if these basic checks are ignored.

As well as regular oil checks and changes, checking the fuel injector nozzles can help to reduce the occurrence of fuel dilution—as dirty nozzles can prevent the fuel from atomizing correctly, and in turn, prevent the fuel from combusting efficiently—so not keeping up with maintenance in this area is another way of increasing the potential for fuel dilution to occur.

Engine Modifications

Modifications to an engine, especially anything that affects the way that fuel is injected into an engine, is another way of increasing the possibility of fuel dilution within the engine oil. This is often manifested through modifications that produce a much greater amount of smoke. The smoke passes by the crankcase before leaving via the tailpipe, so naturally, more smoke is going to enter the oil system which causes the oil to be diluted by the fuel; as well introducing other types of oil contamination.

The Implications of Fuel Dilution in Engine Oil

There are quite a few concerns with fuel dilution which affect the performance of the oil and the engine in general. Over time, excessive dilution can lead to a significant amount of wear, and ultimately, the failure of the engine.

The biggest issue that arises from fuel dilution is the lowering of the oil’s viscosity, as fuel has a much lower viscosity than the oil (as well as possessing a lower vapor pressure and thinning effect), which in turn can cause the oil-fuel mixture to adopt a viscosity lower than it is designed for. This causes the oil to possess less-effective lubricating properties and causes the strength of the oil film to be reduced, which increases the amount of wear on the cylinder liner and the bearings—this arises from the fact that the oil film is crucial for reducing the friction between moving components by providing a barrier, and the thinning of the oil causes the effectiveness of the barrier to be reduced, thus increasing the amount of wear on the system.

There are also many other issues that can occur because of a lower oil viscosity (or a degraded oil in general), and these include reducing the effectiveness of the additives within the oil, increasing the volatility of the oil and increasing the rate at which oxidation occurs within the oil (which then leads to more frequent oil changes).

Sources

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