I am trying to help out a friend - a little history first. He has an 01 whith about 130,000 miles on it. All 8 injecters were replaced a few mounths ago. Approximately 3 mounths later his truck became hard to start, smoked, and had a bad knock. He took it to one dealer and the dealer said the motor needed replacing and it would cost him about $12,000. I conviced him it was more than likely only the injecters. He took it to another dealer and was dignosed with a bad injecter. They replaced only the bad injecter and sent him on his way. One week later he noticed that the oil had fuel in it. He changed oil and took it back to the dealer. Dealer diagoniced that the pump was out (too low of pressure) and that he would need a new pump. It would cost $2000 to rebuild. Also told him the tried and true excuse "your fuel is contaminated".

My question is would the pump putting out low pressure cause it to put oil in the fuel. Approximately 1 1/2 gallons in less than 300 miles?

The pump cannot cause dilution, but the dilution can cause the rail pressure to be low. If there is a fuel leak, the pump cannot achieve desired rail pressure. There is still either a return leak or bad injector causing the dilution. Common practice is to check for proper rail pressure AFTER the injectors/ fuel leaks have been repaired.

Wecome to The Diesel Place.

IMO I would bet on another bad injector. The pump output may have low pressure because the fuel is leaking into the crankcase. Just a guess. I could be all wrong.

Just seems strange no fuel in oil until the injector was replaced and why didn't the dealer see the "pump low pressure/low side of normal" condition when diagnosing the bad injector. It could be that the pump drive end seal is leaking fuel into oil? Don't know that much about the pump but I think that a leaking drive end seal/pump failure would start to happen slowly.

Just throwing out ideas. Good luck with your friends truck.

I have heard that a pump can leak out of the front and into the oil, but have not seen it personally.

I have seen the pump leak into the oil. The pump is not checked much anymore with the new tech bulliten to replace injectors, I think most of us choose to pass that part of the diag.
If done correctly you can flow test the pump output. low flow is either pump issue or a large leak. that bank can go further buy removing the glow plugs and looking for fuel spray. The bad pumps I have seen have had no flow one one bank, or an external leak, and a few cases with internal leaks into oil. Patrick

Sure seems like a lot of trouble for one truck...

Thanks for the replies. Yes is is a lot of trouble for one truck but my gut fealing is it really only had one problem and was not fixed properly the first time.