ok guys i need some help. my buddy got a 95 cummins wit a little fuel issue. it starts up and runs fine for about an hour. then after that it will die. if you are on the interstate, it will buck and kick and sputter and shut off. if u floor it, it will kinda try to come out of it but wont. it also will hold itself wideopen trying to get fuel i guess, idk. and it takes some cranking to get it to fire and it will do this again with a 100 yards. but if ur jus cruising around back roads it will jus die. usually starts back up with not too much trouble.

we replaced then lines from the top of the tank to the lift pump, and the return line. we looked at the shutoff solenoid when the truck shut off b4 he turned the key off and it was still up as high as it would go, then shoot back down when we turn the key off. the fuel heater has been bypassed by the previous owner. everything on the truck is stock too, still has the tamperproof bolt on the pump cover. it is an auto also

any ideas on what could cause this? crack in the lines in the fuel tank? overflow valve or lift pump going out. we r gonna try to get a fuel pressure gauge on it this weekend as he works out of town on weekdays.

we need some ideas on this so lets hear em. i dnt know a whole lot bout 12valves so we need some help.

 

You need to check the fuel pressure.
Does it still quit running with the fuel cap off?

 

Changed fuel filter lately?
Pressure gauge might help narrow it down.

 

yea he changed the fuel filter first thing. where exactly is the best place to check the pressure from on a ppump? what would the fuel cap trick do?

 

Well, sometimes people put the wrong fuel cap on, as in a non vented one.
Then after driving for an hour or so, the vacum builds up in the tank, starving it for fuel. Sometimes the vents get plugged up or don't work even on the correct cap.

 

hmm. ill have to tell him to try that

 

Diesel Dave2 had an issue that sounds exactly like this. Cost him a new injection pump. He also has a 95.

 

ouch. im sure thats not what he wants to hear. any chance u know what it was exactly that it was doing or caused it?

 

I had a similar issue in my 95, it would lose prime over night. I replaced the lift pump and the fuel heater which were upgraded parts from cummins, and the lines related to them and all was good. I would think in Kentucky that you would want a fuel heater too. It was a knuckle-buster since I only have basic toolset, but do-able. Tell your friend it's worth it, get the old crap replaced and its likely that the 12 valve will be like brand new again. I hope it's not the injection pump though, I'm still at 190k on the original injection pump and AT.

 

Checking 12 Valve Fuel Pressure

 

yea we figured we would take a look at the fuel heater later in the year, after we get this figured out and running. thanks for the fuel pressure link infidel. i might see if i can go get his truck and tinker with some of this stuff this week.

 

btw, wheres the best place to get a lift pump if he does need one? our local dodge dealer wants 309 for one.

 

My truck would shut itself down when driving on the highway.Sometimes it would stop in 50 miles,and other times it would be 600 miles.I did every test I could think off....Landed up replacing the IP,no problems after that...but it drove me nuts....I hope you don't have the same problem...

 

did u ever find out what was wrong with the IP when u replaced it?

 

Cummins dealer has lift pumps for $79.

Common problem with '94 and '95 injection pumps is for the DV cylinder bores to warp causing the DVs to stick. Truck loses power, will stall without throttle and sometimes the pump will knock badly.
If you let it cool off for 10 minutes or so it will be fine sometimes for weeks, other times for 10 more minutes.
Someone said that pouring cold water on the pump when it happens will get it going again faster.
Never tried that when mine was acting up.
No problems since replacing my pump. Never found out what exactly was wrong or if it was even rebuildable. The new rebuilt pump I installed wasn't mine, it was an exchange.