I have a 97 cummins that has been running really well until recently - on the flat and up hills it pulls like it is supposed to. It recently started acting up after coming down hills, particularly when pulling the trailer with no throttle and using the engine/trans to keep lower speed. Once I ge to the bottom of the hill and start to throttle, it has no power - cuts out & smokes profusely. After giving it light throttle for awhile, it clears itself up and is running great again. I have replaced the lift pump and overflow valve this week and it did not fix the problem. Please help...

 

what is the color of smoke?

 

it is whitish gray

 

Has your fuel pressure and volume been verified? Have you watched the pressure when this occurs?

 

I have not had any of this verified and don't have a fuel pressure gauge. This truck runs great any other time and has just recently started doing this. I have pulled 40' shipping containers up several large hills the same day that this problem occurs. It is only after I have let the engine slow the truck down and start to throttle up again. Once all of the excess fuell burns off, it is running great again.

 

Could be timing related, could be all kinds of things. You'll need to do some diagnoses of your own before anyone here can help you. Otherwise we're just guessing

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ps snap on has fuel pressure sets on sale right now.