Advice - Diesel fuel in my engine oil

[henrymei]

Fuel in the oil can lead to a runaway. This happened to me on a 3208 when an injector line broke under the valve cover. Not a fun experience.

 

[C lectric]

I will add that if you do not have fuel in the VEE near or under the PT pump then it is almost guaranteed that you have at least one injector in trouble.

When I removed mine several of the O rings fell apart. I was told that when the injection shop started work the rest of the O rings fell apart. Even if the O rings don't disintegrate in place if they crack that is enough to allow fuel to bypass them and then the fuel can get into the oil.
O rings also lose resiliency as they age and may contract a bit again allowing leakage. They last a long time and many hours but like all thing they have a life span.
My engine is a '77 with just a bit under 7,000hrs.

 

[White River Dream]

VT903M were the primary engines used in CG 41' Utility boats.

There is no diaphragm on these fuel pumps. The transfer pump is gear operated of the timing gears, the PT (Pressure/Time) pump is not a typical injection pump. It only raises the fuel rail pressure in the common rail 25psi min cranking, 270+psi when you snap the throttle running (must use a 0-400psi liquid filled gauge to test.) The unit injectors then achieve injection pressure by the third rocker arm.

The injectors are inside the valve covers bolted into the heads as was shown above. Three rubber o-rings. If they leak the fuel will flow up into the valve covers quite easily. With the valve covers off this is usually easy to spot as the fuel will flow while cranking & wash the lube oil away from the injector. If it starts you will almost certainly see it.


If one is leaking I would put new o-rings on all in that head at least.
They either leak from being nicked/cut during install or last until the next overhaul. Unless someone over heats that head, they dry out and crack.


This is a link to an explanation of the Cummings PT fuel systems:
https://constructionmanuals.tpub.com/14264/css/Cummins-Diesel-Fuel-Systems-189.htm

Thankyou so much I really Appreciate your help in this situation.

 

[C lectric]

Does this Cummins V 8 have a similar fuel piping setup to the Cat3208? The Cats can leak diesel in the valley area and then into oil.

No, different from the 3208.

The PT pump, which can leak and SOMETIMES dumps fuel into the oil. However that is quite rare. THere are two seals on the PT drive shaft. One for the engine oil, one for the fuel. It can leak into the VEE but there is not an easy path into the oil that way. It will run over the back of the engine and over the bellhousing, USUALLY.
From the PT pump there is ONE line that goes to the cylinder head , on mine the Port head, then branches to the Stbd. head when facing the engine front.
The PT pump simply varies voluum and pressure to the injectors. After that it is the injectors that do the delivery and really crank up the pressure.


The final fuel delivery to each injector is fed by a common gallery to all injectors in that head . Any excess fuel uses a different gallery and returns to the tank. That fuel is HOT as it is used to lube the PT pump, the injectors AND at the same time cool them.

There are NO individual tubes/lines to OR from the injectors.
Just the ones described.

I hope this helps.

 

[C lectric]

I will suggest again that you either go to Boat Diesel and down load the owners manual or PM me and I will Email the 5 parts to you.

Unless of course you already have the owners manual and it describes the adjustment and how the system works.

 

[White River Dream]

Fuel in the oil can lead to a runaway. This happened to me on a 3208 when an injector line broke under the valve cover. Not a fun experience.

Yes I completely understand that I have never witnessed it but there is nothing good about a runaway motor

 

[White River Dream]

No, different from the 3208.

The PT pump, which can leak and SOMETIMES dumps fuel into the oil. However that is quite rare. THere are two seals on the PT drive shaft. One for the engine oil, one for the fuel. It can leak into the VEE but there is not an easy path into the oil that way. It will run over the back of the engine and over the bellhousing, USUALLY.
From the PT pump there is ONE line that goes to the cylinder head , on mine the Port head, then branches to the Stbd. head when facing the engine front.
The PT pump simply varies voluum and pressure to the injectors. After that it is the injectors that do the delivery and really crank up the pressure.


The final fuel delivery to each injector is fed by a common gallery to all injectors in that head . Any excess fuel uses a different gallery and returns to the tank. That fuel is HOT as it is used to lube the PT pump, the injectors AND at the same time cool them.

There are NO individual tubes/lines to OR from the injectors.
Just the ones described.

I hope this helps.

Yes It really does I am understanding more and more about the system from this form. I finally received a repair manual but it did not cover the injector pump or injector is very disappointing on that. At this point I think I am going to start by just simply removing these injectors and having them rebuild and go from there.

 

[White River Dream]

I will suggest again that you either go to Boat Diesel and down load the owners manual or PM me and I will Email the 5 parts to you.

Unless of course you already have the owners manual and it describes the adjustment and how the system works.

I received the manual but was disappointed when it did not cover the breakdown of the injector pump and injectors for that matter. But I have read a lot of it thus far. The rocker arms and rails and inside the heads look super clean. This could be from leaky injectors also or just that the motors are in pretty damn good shape. Hard to say at this point. Because my oil has so much fuel in it I do not want to turn it over. To check and see if the injectors are leaking. The oil viscosity must be pretty weak at this point and I just don’t feel good about cranking the motor with oil like that. But as it cost $100 just to put oil in this thing I don’t want to waste another hundred dollars on oil just to turn it over and watch the injectors to see if they are leaking. I must admit I was hoping for a quicker fix. I was hoping that it was a diaphragm or O-ring on the fuel side. But I have learned about the system in this PT pump and as you said only two O-rings and more than likely not responsible for the fuel in the crank case. At this point I am just going to have to yank the injectors. I did have a question and I can refer back to the manual but was wondering can I Possibly remove the injectors without removing the whole rocker arm rail and having to do all the valves Adjustments over again? Reading the manual I have discovered that it is quite a chore and time-consuming to adjust all of the valves and injectors

 

[C lectric]

You won't likely get a manual that details the injector or PT pump adjustments. Because of the way the system is designed there are a lot of adjustments and some equipment is needed to test those adjustments.

I simply took my PT and the injectors to the Cummins dealer and distributor and they looked after it. THe PT was re/re by the local Cummins.
THe injectors were sent to Alberta where there are still many of these engines in operation apparently

They will look at the embossed plate on the PT which then gives them all the info needed for THAT pump.
Make sure they know which engine it is on also. THe HP and the engine serial number.

Do regular oil tests. That is what confirmed and tipped me off that I had a problem brewing.

Know where the oil pressure sits normally. If it starts to show low when you are operating at your normal revs then be wary and do a test.


As for testing you could disable the PT fuel output valve by removing the solenoid activation wire. THat solenoid is what allows the engine to run and to shut it down.

Pull that wire and it cannot start. The only catch is that the PT can't deliver fuel then so the leaking may not show. Don't drop the nut. If I remember correctly it is a #12 which is often not readily available unless a good hardware or fastener place is available. Can't remember the pitch., I Got caught on a Sunday.

Now i have a few in my kit although it would take some searching to find them

 

[White River Dream]

You won't likely get a manual that details the injector or PT pump adjustments. Because of the way the system is designed there are a lot of adjustments and some equipment is needed to test those adjustments.

I simply took my PT and the injectors to the Cummins dealer and distributor and they looked after it. THe PT was re/re by the local Cummins.
THe injectors were sent to Alberta where there are still many of these engines in operation apparently

They will look at the embossed plate on the PT which then gives them all the info needed for THAT pump.
Make sure they know which engine it is on also. THe HP and the engine serial number.

Do regular oil tests. That is what confirmed and tipped me off that I had a problem brewing.

Know where the oil pressure sits normally. If it starts to show low when you are operating at your normal revs then be wary and do a test.


As for testing you could disable the PT fuel output valve by removing the solenoid activation wire. THat solenoid is what allows the engine to run and to shut it down.

Pull that wire and it cannot start. The only catch is that the PT can't deliver fuel then so the leaking may not show. Don't drop the nut. If I remember correctly it is a #12 which is often not readily available unless a good hardware or fastener place is available. Can't remember the pitch., I Got caught on a Sunday.

Now i have a few in my kit although it would take some searching to find them

Yes at this point I am going to send the injectors and the PT pump out and have them rebuilt I do not know enough about them to do it myself. Not like rebuilding and Edelbrock carburetor or something LOL also I think it would be impossible to detect a fuel leak from the injector without some type of pump pressure. But my main concern is the velocity of the oil because it has been saturated with diesel fuel so much in such a short amount of time. And I do not care to put all new oil in just to turn around and contaminate it with diesel fuel. At this point the injectors or first to come out and inspect o-rings and go from there.

 

[C lectric]

I wrote this for my V555 to help a few others since I did mine.
Your 903 should be similar, just bigger. THere may be some differences though.


Hope it helps

 

[White River Dream]

I am starting this job Monday morning going to remove the injectors first. I feel that the O-rings will probably tell me everything I need to know. The information you sent me is golden and I really really appreciate it. As I said I have been a mechanic for more than 40 years but diesels have never been my expertise. And these Cummins are definitely a different animal than the diesel motors I have played around with. I will keep updates on how everything goes and what I find wrong. And hopefully this will help others along the way.

 

[C lectric]

The tools I forgot to mention I found on Ebay over a period of time.
Some of them are still available new but are $.

Happy wrenching.

 

[ronobrien]

Thank you for getting back to me. The fact of the matter is these motors have not run for a long time but are what appears to be very good shape. I bought the boat a year ago and I am now firing the motors for the first time. I have been a mechanic for 40 years but not a diesel mechanic. The starboard side motor fired up and ran good and I am not showing any signs of fuel in the oil. When I turned over the port side motor there was a small hole in the oil filter. So I immediately addressed the problem and by doing so also found that the oil was overfull when I drained the oil I found that it had diesel fuel in it. I put all new oil in it. Turn the motor over a few revolutions But he did not want to start. Re-checked oil and now I’m finding that the oil is a little watered down with fuel and I can smell the diesel in it. I have been told by a diesel mechanic that it possibly has a cracked injector he wants me to pull all of the injectors and have them checked.

I would go with Rochepoint's comment. It makes more sense and is way less expensive. Just change out the lift pump and see what happens.

 

[C lectric]

THERE IS NO LIFT PUMP on these older Cummins engines.

 

[Steve1.0]

Does this Cummins V 8 have a similar fuel piping setup to the Cat3208? The Cats can leak diesel in the valley area and then into oil.

Not to high-jack the thread but;
I found fuel on top of my stb. engine (3208TA) after my last run of about 7hrs. From where would it be leaking?



And how do you stop a run-away 3208?

 

[ghost]

Not to high-jack the thread but;
I found fuel on top of my stb. engine (3208TA) after my last run of about 7hrs. From where would it be leaking?



And how do you stop a run-away 3208?

https://www.trawlerforum.com/forums/s6/cat-3208n-issues-25992.html

 

[FF]

And how do you stop a run-away 3208?

This is usually a Detroit 2 stroke problem , from a stuck injector , or so much wear that the engine is operating on its lube oil that is getting past the piston rings.

Blocking off the intake will stop the engine.

DD even has emergency stop shutters on some road engines .

Shutting off the air should stop most any diesel.

BE ready, find a piece of 3/4 ply that can be easily held against the intake.

Although on a maintained engine its a VERY rare problem.

 

[C lectric]

*********also I think it would be impossible to detect a fuel leak from the injector without some type of pump pressure.**********


Your comment above reminded me of something.

Yes, the injectors can be tested for leakage by capping/plugging the output return line port at the back of the head and pressurizing the supply at the head front. Then watch for fuel. No running the engine, just a small pump and some wrenching. Never having done that though I don't know what pressure.

For me I didn't care, they were going to be redone with new O rings and a rebuild or I would be doing it again in a year or two for a different O ring.

Since mine were done the engine starts quicker with less smoke, idles better and , I THINK, is quieter, not much maybe but I think.

 

[White River Dream]

You know I hadn’t thought of that, really good idea. These motors were said to have been rebuilt a few years ago and then never really used as the owner fell sick and eventually passed away. The boat sat here in the harbor for a good four years maybe longer before we bought it. I would imagine and/or maybe not that the same could be true about pressurizing the fuel pump and seeing if I am able to pass fuel into the crank case that way. If it was only turned over a minimal amount of revolutions and yet I am now looking at a good gallon over the dipstick level then it had to of siphoned into the crank case through time and not just from the cranking of the motor. Was planning on starting the wrenching on it yesterday but have not had time and now with the Thanksgiving holiday probably won’t get started on it until next week. Still reluctant to pull all the injectors without knowing for sure if this is where the problem is coming from. Sure wouldn’t mind so much if they weren’t so difficult to Pull and then readjust all the rocker arms. Otherwise would have been done already. I like your idea and I may very well do that first. If the O-rings are good they should hold up to 10 or 15 psi worth of pressure with out failing As soon as I get to turning some wrenches on this motor I will be doing updates on what I have found what tests I have done. Again I really like your idea��

 

[ronobrien]

*********also I think it would be impossible to detect a fuel leak from the injector without some type of pump pressure.**********


Your comment above reminded me of something.

Yes, the injectors can be tested for leakage by capping/plugging the output return line port at the back of the head and pressurizing the supply at the head front. Then watch for fuel. No running the engine, just a small pump and some wrenching. Never having done that though I don't know what pressure.

For me I didn't care, they were going to be redone with new O rings and a rebuild or I would be doing it again in a year or two for a different O ring.

Since mine were done the engine starts quicker with less smoke, idles better and , I THINK, is quieter, not much maybe but I think.

I don't know the specification for this engine's injectors, but back in the day when I worked for Mack Truck, the injectors wouldn't open or "pop" until approximately 4000psi. This varied between engine design, HP and model year. You idea of a pump is good in theory, but you won't generate the pressure required to test them. If the spec was 4200psi, we might see i drip at 3900, which was NG. So lower pressure testing is not effective.

 

[White River Dream]

The pump system on this motor is a low pressure system the pressure comes from the rocker are pressing the plunger in the injector. I am simply trying to find a fuel leak around the O-rings. Don’t know how much fuel pressure it would take to achieve that. But I wouldn’t think much.

 

[ronobrien]

The pump system on this motor is a low pressure system the pressure comes from the rocker are pressing the plunger in the injector. I am simply trying to find a fuel leak around the O-rings. Don’t know how much fuel pressure it would take to achieve that. But I wouldn’t think much.

Understand. I thought you were trying to find an internal injector leak (drip). A leak that I am describing could add fuel to the sump, but would likely damage pistons as well. Sounds like you have a good idea. Good luck.

 

[C lectric]

I don't know the specification for this engine's injectors, but back in the day when I worked for Mack Truck, the injectors wouldn't open or "pop" until approximately 4000psi. This varied between engine design, HP and model year. You idea of a pump is good in theory, but you won't generate the pressure required to test them. If the spec was 4200psi, we might see i drip at 3900, which was NG. So lower pressure testing is not effective.

ronobrien
I am not discounting your experience BUT
I was told this was an effective test method by a Cummins mechanic at the main area distributor when I went to talk to them. This test is not trying to POP the injectors, rather test the O ring seals ability to hold a seal between the injector body and the cylinder head bore.

You won't be looking for the injector itself as a leak point. It may be if the plunger tip no longer seals so then it dribbles.

The more likely source of a higher fuel volume are the O ring seals on the injector body. That will allow fuel to get into the rocker area of the head.

I did not do that since I had decided that if I was in for some work then I wanted it ALL done or it would be another job next year when the next O ring failed. In my case the engine is 43 yrs and a hair under 7,000 hr.
THe O rings were breaking apart when the shop was trying to remove them.

They do age out as do ALL O rings.

Which brings up a point. THe bulk of the work is getting access and then the adjustments. Personally I would pull them all and then you start afresh for the next 20 - 30 yrs or you take a chance of a repeat in a year or two especially if those O rings are simply ageing out.

Believe me, I understand your frustration. I looked around my small town for someone to do the work and realized I know more about MY engine than they did. I finally bit the bullet and did it myself.

But do the leak test job just for the halibut.

Good luck and if I can help in the future PM me.

 

[twistedtree]

I agree with C lectric that proactive replacement of the injector seals makes sense if you are digging in there. But I still worry that it might not be the cause of the leak, and it would really suck to go through all that work and still have a leak.


The good news is that the leak seems pretty massive based on how quickly your oil dilutes out. So I think it's worth carefully inventorying all the possible leak points, and addressing them. I just hate doing a fix based on hope and a prayer that it's the problem. I'd feel so much better if you were able to actually get eyes on the leak source.


It's hard to offer more without knowing the PD system, but I'd be looking at the whole fuel path. For example, is there any way for fuel to leak out of the gallery in the head by way of a failed head gasket? Also, could failed or torn seals in the low pressure pump drive fuel into the timing case around the drive gears? I like the idea of pressurizing with air. Could the pump be pulled then pressurized to check for leaks there? And what about the fuel return path? Any seals there that could allow fuel to get into the oil?


Oh, one more thought. If you pressurized the fuel system at the inlet to the pump, and cap off the return, we are expecting it won't hold pressure because of your leak. If you then can cap off the outlet of the pump, and it still leaks, then you know the leak is in the pump. If it hold pressure, then you know the leak is in the heads/injectors. You could then cap off to each head in succession (I'm assuming the pump delivers separately to galleries in each head) to further narrow down where it's leaking.

 

[White River Dream]

Yes I basically agree with everything you’ve said all along. I don’t have 20 or 30 years to live for that matter LOL I am 62. Would be nice to believe that. If I could get 10 years out of this ship I would be pretty happy. We are not chartering fishing partys or anything like that. Simply a weekend warrior type thing with this boat. And seasonal for that matter. But I’ll do some testing first and see what happens and that will probably give me a good idea where I’m at with this. Better to do all the work in the long run then to cause damage to the crank bearings or any of the internals for that matter with Diesel in the oil. As I said before when I get started on this I will post and keep updating the results.

 

[Island Cessna]

My recollection is that the PT pump puts out a variable pressure in the range of 50 to 400 psi.

The cam operated injector boosts this up to the several thousands of psi noted above at the nozzle.

Bill

 

[ronobrien]

ronobrien
I am not discounting your experience BUT
I was told this was an effective test method by a Cummins mechanic at the main area distributor when I went to talk to them. This test is not trying to POP the injectors, rather test the O ring seals ability to hold a seal between the injector body and the cylinder head bore.

You won't be looking for the injector itself as a leak point. It may be if the plunger tip no longer seals so then it dribbles.

The more likely source of a higher fuel volume are the O ring seals on the injector body. That will allow fuel to get into the rocker area of the head.

I did not do that since I had decided that if I was in for some work then I wanted it ALL done or it would be another job next year when the next O ring failed. In my case the engine is 43 yrs and a hair under 7,000 hr.
THe O rings were breaking apart when the shop was trying to remove them.

They do age out as do ALL O rings.

Which brings up a point. THe bulk of the work is getting access and then the adjustments. Personally I would pull them all and then you start afresh for the next 20 - 30 yrs or you take a chance of a repeat in a year or two especially if those O rings are simply ageing out.

Believe me, I understand your frustration. I looked around my small town for someone to do the work and realized I know more about MY engine than they did. I finally bit the bullet and did it myself.

But do the leak test job just for the halibut.

Good luck and if I can help in the future PM me.

I did reply to another comment that I misunderstood the intention of pump setup. Also my experience is different with an externally injected engine compared to that of the Cummins which has an internal common rail. I did not think of that fact. Thanks.