6.2 lack of power

[CWW]

I am new to diesels and have owned my 84 cucv m1028 for about a year. It has 38k miles, 6.2,th400 np208. When i got the truck i was told it had a rebuilt injection pump and it drove well. But for the last 6-7 months the truck just doesn't seem to have any power. It accelerates ok when cold but as soon as the truck gets hot it does not want to accelerate. If it is stopped on a hill it will barley move or not move at all and when accelerating from a stop it is very slow. When I changed the oil a week ago the oil was grayish and thin. It starts fine wether cold or hot. Now it is leaking diesel from what looks like the rear injectors on both sides, but i did not see any leakage around the injection pump. Any help would be appreciated.

[88 K30]

Thin, gray oil is a bad thing. Perhaps the oil is being contaminated by diesel from a bad lift pump diaphragm? Did the oil smell like diesel?

[CWW]

I don't really get a strong smell of diesel from the oil, but the oil definately does not smell normal.

[john8662]

With the oil being thin, you'll have to see if the oil level is rising.

Possible fuel contamination.

If this is the case, there are two suspects. The lift pump and the injection pump.

Yes, the injection pump can fail (early production pumps) and allow fuel to enter the crankcase.

Either of which would lead to low power and contaminated oil.

J

[CWW]

Thanks for the input. I am going to change out the lift pump and see if that does anything.

[CWW]

I replaced the lift pump but there is still a lack of power. Is there anything else besides the injection pump that could be the cause?

[CWW]

Finally replaced the injection pump. Man what a difference it made. The truck really moves now.

[FEF]

So we can assume the injector pump was the problem. That probably wasn't very cheap.

I'm still courious if it fixed the oil contamination issue.