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Old 25-09-2017, 03:34   #1
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Diesel fuel in oil

Last week I replaced the fuel lift pump in my Perkins 4-108 due to fuel getting into the sump oil. It seemed to have worked. I changed the oil, ran the engine 1 hour to get home, changed the oil and filter, ran for 1 hour, checked oil, ran 1 hour again next day, checked, level all fine. Today, after letting the engine sit all weekend, the oil level is high again.
How would fuel be getting into the sump when the engine is sitting idle?
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Old 25-09-2017, 04:08   #2
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Re: Diesel fuel in oil

Try a diesel leak off test - kits are cheap and easy to use.

Sounds link an injector passing for the residual pressure when engine stops.

HTH
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Old 25-09-2017, 04:14   #3
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Re: Diesel fuel in oil

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Originally Posted by paulajayne View Post
Try a diesel leak off test - kits are cheap and easy to use.

Sounds link an injector passing for the residual pressure when engine stops.

HTH
Thank you. I'll try to get a kit.
If one of the injectors is leaking, is it just a matter of replacing the injector?
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Old 25-09-2017, 04:43   #4
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Re: Diesel fuel in oil

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Originally Posted by shanegeard View Post
Thank you. I'll try to get a kit.
If one of the injectors is leaking, is it just a matter of replacing the injector?

Yes or get a refurbished one.

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Old 25-09-2017, 04:49   #5
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Re: Diesel fuel in oil

Thank you!
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Old 25-09-2017, 06:05   #6
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Re: Diesel fuel in oil

You can also take your injectors off and bring them to get tested. Should be fairly cheap.
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Old 25-09-2017, 06:13   #7
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Re: Diesel fuel in oil

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You can also take your injectors off and bring them to get tested. Should be fairly cheap.
Yes that sounds a good idea. I believe they should get a service every 1000 hours anyway.
However, I dont understand how a faulty injector would cause fuel to leak into the engine oil.
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Old 25-09-2017, 06:44   #8
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Re: Diesel fuel in oil

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Yes that sounds a good idea. I believe they should get a service every 1000 hours anyway.
However, I dont understand how a faulty injector would cause fuel to leak into the engine oil.
Drips into cylinder then works it's way down cylinder wall. Not sure this would cause a noticeable rise in oil level in the pan in the time frame stated tho'.
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Old 25-09-2017, 06:53   #9
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Re: Diesel fuel in oil

We had a leak via the high pressure pump (injector pump). The pump is driven by a shaft which has a seal that can deteriorate. This is what happened to ours. We would get diesel spilling into the case, but it only seemed to happen in certain RPMs. The problem was erratic, and I never did fully figure it out fully, but this was definitely the source. We had the pump rebuilt. All has been well ever since.

BTW, we initially thought it was the lift pump. All the experts said this was the most likely cause, but after replacing this pump the problem remained. But due to the erratic nature of the problem, it looked like the lift pump fix actually worked for a while.
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Old 25-09-2017, 07:10   #10
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Re: Diesel fuel in oil

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We had a leak via the high pressure pump (injector pump). The pump is driven by a shaft which has a seal that can deteriorate. This is what happened to ours. We would get diesel spilling into the case, but it only seemed to happen in certain RPMs. The problem was erratic, and I never did fully figure it out fully, but this was definitely the source. We had the pump rebuilt. All has been well ever since.

BTW, we initially thought it was the lift pump. All the experts said this was the most likely cause, but after replacing this pump the problem remained. But due to the erratic nature of the problem, it looked like the lift pump fix actually worked for a while.
Thank you, that sounds like what is happening here. Anyone know of someone in the Brisbane Queensland area that can do this? I'm ok with removing the pump and possibly refitting it, but the rebuild sounds specialized.
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Old 25-09-2017, 09:44   #11
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Re: Diesel fuel in oil

And here I am thinking broken ring or hole in the piston where a stuck valve got it ? I would definitely be doing some compression testing to be sure!
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Old 25-09-2017, 09:58   #12
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Re: Diesel fuel in oil

I have had the same problem and it was the seals on the injector pump. You can change these yourself just google injector pump seals. Although how diesel is getting in there when the engine is not running baffles me. Best of luck.
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Old 25-09-2017, 09:58   #13
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Re: Diesel fuel in oil

I dont think a bad injector is going to put enough diesel in the pan to notice if the engine is off. It would be very low on my things to investigate. JMHO.
BTW, tht engine can run quite well and smooth with one cylinder not working.
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Old 25-09-2017, 10:03   #14
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Re: Diesel fuel in oil

I should have added. Make sure that you get the manufacturers seals for the pump or the same may happen again. All seals are not equal !!!
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Old 25-09-2017, 10:27   #15
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Re: Diesel fuel in oil

Here is some great info on fuel injectors


https://youtu.be/XhYEDkpF3Qs
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