Truck bogging down

I am posting this for my brother-in-law, so my first hand knowledge of the information is limited. He has a 2003 Chevrolet 2500 with the 6.6L Diesel engine. He says the problem is when he takes off or “gets in it” the truck bogs down/smothers and appears to be almost dying. He says he can let up and ease back into it and the truck will operate normally. Th check engine light is not showing so I don’t have any codes to work off of. I think he has had problems similar to this with water in the fuel filter before, a common problem I understand with Diesel engines. Anyone have any ideas? I know very little about diesel enginoto be of help to him.

I guess you answered your own question.

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I thought this might be the issue but I wanted to make sure there wasn’t something else that could be the culprit.

Check the fuel pressure.

A diesel engine must have good fuel pressure.


There should be a water separater before the filer that need’s drained every so often.

The fuel filter must be replaced every 30,000 miles, with or without fuel contaminated with water. Dirty fuel filters are a common cause of diesel performance problems.


The Duramax has a water sensor on the bottom of the fuel filter, which should trigger a “water in fuel” message on the instrument cluster message center if there is water in the filter.

Preliminary checks for loss of power always start with filters, both fuel and air. Check for fuel contamination, either by water or fungi. If those are okay, then diagnosis proceeds with sensor inspection (fuel rail pressure and the CKP reluctor), followed by fuel, exhaust, and air intake system checks, etc.

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He took it by a shop and changed the fuel
Filter. The one on there was only a 1/3 of the size of the new one. Runs great now.