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Curtis B.
Curtis B., Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 26021
Experience:  Technician turned service manager on multiple lines of trucks and engines, used in industry.
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2008 GMC with 7.8 Liter Isuzu diesel. Have fuel in the oil

Customer Question

2008 GMC with 7.8 Liter Isuzu diesel. Have fuel in the oil
Submitted: 6 months ago.
Category: Medium and Heavy Trucks
Expert:  Curtis B. replied 6 months ago.

Fuel in the oil will come from a fuel transfer pump driven off the camshaft, or from the injection pump drive shaft. Engine has pencil type injectors and they will not cause fuel in the oil. Where is the fuel transfer pump? It is the most common problem.

Customer: replied 6 months ago.
it has a new injection pump and there is no lift pump
Expert:  Curtis B. replied 6 months ago.

Same problem with the old pump?

Expert:  Curtis B. replied 6 months ago.

Electric pump in the fuel tank for transfer?

Customer: replied 6 months ago.
same problem with old pump, yea in tank transfer pump
Customer: replied 6 months ago.
putting 2 quarts of fuel in oil every 1000 miles
Expert:  Curtis B. replied 6 months ago.

Injectors are external with high pressure lines from the injection pump? With no transfer pump, I see no other place that fuel can cross over to the engine oil.??

Customer: replied 6 months ago.
injectors were tested and all said to be good
Expert:  Curtis B. replied 6 months ago.

Only thing that it can be is the injection pump! Have you talked to rebuilder?

Customer: replied 6 months ago.
truck was at isuzu for three weeks and they threw there hands up
Customer: replied 6 months ago.
the injection lines feed through the head could be return lines or pass through to injector leaking
Expert:  Curtis B. replied 6 months ago.

I would not rule it out, but seems like Isuzu would have found it!

Expert:  Curtis B. replied 6 months ago.

I would not rule it out, but seems like Isuzu would have found it!