Buddies 08 problems

cerickson

cerickson

fullpull108
Post up to try to help a buddy that has an 08 3500. Truck runs fine when empty. Everytime he hooks his fifth wheel trailer on and hit a hill the truck goes into limp mode. He bought a scan tool to see what the codes tell him when it does it. He clears them. But the truck still stays in limp mode. It is totally stock. Original injectors as far as he knows. He has replace all the rubber fuel lines from the tank forward.

I know nothing about these engines. So I figured I would ask for some help for him.
 
I told him I thought it could be a fuel rail pressure spike. He says he can run the truck hard empty, but it won't do it till he's hooked to his trailer. Runs out good on the flats. Hills are what sticks it in limp mode.
 
My brother n laws 08 did the exact same thing, would run fine but when hooked to a trailer or ran hard at all would go into limp mode, it was the trans.
 
My best friend's LBZ did the same thing, only when towing and only on the hills then he got on it. The code was 00087, low rail pressure. We plugged the return on the rail and it didn't help. This is a stock LBZ except it has a tow tune in it by Idaho Rob. Had Rob test everything and couldn't find the problem, changed tunes and everything. Finally turned off the limp mode for the engine. Problem solved. The check engine light will still come on and it will set codes but it won't go into the dreaded limp mode. The limp mode for the tranny is still on. If the engine will only rev to about 2000 rpm but shift it the engine limp mode. If the truck get stuck in a particular gear, it's a tranny limp.

Another potential problem is the return line from the CP3 pump. Another guy had his do the same thing, totally stock and would engine limp towing and getting on it usually on a hill. Replaced the return line where the kink was, end of problem.

Hope this helps.
 
Thanks subman. Told him to check out this page for some help. Maybe he will join. I told him it's pretty much a Cummins site, but alot of the guys on here know alot about all brands.
 
Lol he said if I wanted to buy it. Said he should of bought a Dodge. Told him there is good and bad with all of them.
 
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