Diesel in oil

[redneck1317]

I have a 2004 1 ton Duramax and I'm getting diesel in my oil. I don't drive it alot so I just noticed this when I slowed down and the oil pressure dropped to about nothing,but when I took off it picked back some.About a yr and a half ago I had a new fuel pump that mounts on the passenger side of motor up front was about 1200 dollars. I was just wondering was there any way that the diesel could get in the oil from their. Thanks for any help.

[AKMark]

Typically it happens when the injectors give up the ghost.

[redneck1317]

whats that mean and it was the injector module that i had changed.

[DmaxMaverick]

Unless you added one, there is no "fuel pump" located at the passenger side of the engine. There is, however, a fuel manager (filter assembly, with hand pump), and a vacuum pump (on some models).

Which engine series do you have? Early 2004 were LB7, and later 2004 were LLY. The 8th digit of the VIN will indicate which. 1 = LB7, 2 = LLY.

The LLY engines do not have an issue with the injectors leaking fuel into the crankcase. The high pressure fuel pump (located at the front of the engine valley), on the other hand, can. It isn't common, and is extremely rare.

The LB7 engines have the injectors under the valve covers, and can leak fuel into the crankcase when they fail. Their fuel return lines are also under the valve cover, and will leak fuel into the crankcase if they crack, or leak otherwise. And, like the LLY, the high pressure fuel pump can leak fuel into the crankcase, but also like the LLY, extremely rare.

If your engine is an LB7, there is a high probability of injector failure. The fuel return lines can fail (usually a crack), after an injector replacement, or for no reason at all.

[redneck1317]

it is the LB7 and it was a Injector module that i had replaced and it wasn't long after that when I noticed the oil pressure dropped. That may not have had anything to do with it, just checking because I didn't know.

[DmaxMaverick]

The FICM, or driver module, has fuel passing through it as a cooling function, but has NO interface with engine oil. They can fail or leak, but they can't allow fuel into the crankcase.

If you are making oil, it's either the injectors (likely), fuel return lines (less likely), or the high pressure fuel pump (extremely less likely). In any case, it should be properly diagnosed, rather than just throw parts at it. Soon. Enough fuel in the oil to cause the pressure to drop is significant, with the potential to cause extensive engine damage if ignored. If you MUST drive it (emergency), keep the oil fresh and as undiluted as possible, and limit running time and hard driving.

[redneck1317]

Thanks for the info. I'll get it checked out