Engine/Transmission (1994 - 1998) Stumped ! losing prime...

[Hoof Daddy]

I'm really puzzled, for the last two months I've been chasing a fuel system losing prime. First I've traced and inspected from the fuel tank, to the lift pump, fuel filter, to the injection pump, to the injector's, return lines back to the fuel filter, also from the overflow valve back to the fuel tank. I replaced the lift pump, Overflow valve ,the ball check on top of the fuel filter returning from the injector's. I cannot smell or see any diesel leaks, that's why I thought I had an internal problem. I put new hose's on the supply and return lines from the fuel tank but so far nothing has help. if it set's and hour it get's a little cranking problem if it set's overnight it's very hard to crank unless I use the manual prime button on the lift pump. Which is as we know a hassle. Any thought's or suggestion's would be appreciated. Hoof

 

[Joe G.]

Try removing the fuel heater.



Take a look at the pictures I posted to this thread: https://www.turbodieselregister.com/forums/showthread.php?t=111294

 

[Hoof Daddy]

Thanks Joe for the info, I've replaced the original one about two years ago just because it had been on for so long. You think I might just replace it just to eliminate from being a problem ?

 

[scramblin]

Thanks Joe for the info, I've replaced the original one about two years ago just because it had been on for so long. You think I might just replace it just to eliminate from being a problem ?

Had the same problem with a 94 once. It turned out to be a fuel filter o ring. It had a small flaw.

 

[Hoof Daddy]

The one where the fuel wtr sensor is ? Or the one around the threads where the filter screws on. Thanks for the help I guess I'll go and purchase a new filter and change both. I confess I dont always change the one around the threads.

 

[Scot]

I was having trouble getting fuel on the project and found the hose between the heater and lift pump to be bad.

 

[Joe G.]

The fuel heater is easy to take out for a test to see if the problem goes away. Unless it's really cold in the winter you can do without it. There are a lot of things that can cause this problem. I had a small leak and hard starting once that turned out to be the double banjo fitting on the input side of the fuel filter. Bad gaskets.

 

[scramblin]

The one where the fuel wtr sensor is ? Or the one around the threads where the filter screws on. Thanks for the help I guess I'll go and purchase a new filter and change both. I confess I dont always change the one around the threads.

Yes. It was the one where the H2O sensor is. The part that is hard to understand is, it didn't leak fuel, it sucked air.

 

[Hoof Daddy]

Well I went and pickup a new fuel filter FS 1253 and replaced both the O-ring and filter housing stem gasket , I have to work tonight so I didn't have time to try the fuel heater yet. This was the easiest to tackle before I go in. I know in a few hours if that solved it. When I pulled the filter to change it out I noticed it was only half full..... ? So I'm getting close I hope. Also I purchased a new Fuel wtr sensor. If this dont work I'll attack the fuel heater and hose between the Lift pump next. Thanks again for everyone's input I'm not discounting anything.

 

[Hoof Daddy]

Thanks to everyone who helped , I finally figured out what was the problem. I did replace the Pre-filter but ended up changing the Lift pump AGAIN I concluded the ball check in the one I got from local Cummins shop even though new was faulty. The fuel filter was draining back to the fuel tank,and that's where the problem was. Only after changing the Lift pump again did it stop and the system started operating properly. No I didn't buy the last Lift pump from Cummins but I will soon be heading back to get my money back for the one I bought from them. Lot's of headache's this problem has been.

 

[MD500E]

I helped a friend with the same problem on a 98 12 valve. He finly got fed up and we replaced all of the lines, got rid of all of the quick-disconects, replaced the lift pump, and cleaned out the fuel tank. While putting it back together, just for fun I pressure tested the pre heater housing and found it leaking badly at the electrical conectors. Since this is before the lift pump, it is on the suction side and was constantly introducing air. -Kevin

 

[st louis assembly]

fuel drain back

Cummins replaced the "injector pump anti drain back valve" and that solved my hard to start problem. Now I am just trying to find out where the heck the thing was located.