New to this forum, new to Cummins. I purchased a 94 for my Son 2 months ago (125K miles). It ran perfect until a week ago. It now is hard to start, but once running, seems to run ok. When we try to start it, it fires once and dies. If you keep trying to start it, it will eventually run on the 4th or 5th try. I believe it's sucking air, my Son thought it was the fuel filter sucking air. We replaced the fuel filter, cracked the injectors to bleed them, and after that it fired right up. We let it sit for an hour, and it hard started again. Are we on the right track thinking it's an air leak. if so, where should we start looking?

Thanks

 

Look over the entire fuel system with a fine tooth comb for leaks.

 

also check the fuel shut off behind the injecter pump,check to see if it sucks up with the key on, these can hang up and be intermitent.

 

Checked all the lines from the tank, to the injectors, don't see any visable signs of anything leaking. Checked the lines with the key on and lift pump running, checked the lines with the engine running. Did find a bolt missing on the AFC housing, replaced it, but still does the same thing. Is it possible that the lift pump itself could be loosing pressure and sucking air???. Tried starting it this morning, and it took 7 tries before it would keep running. Again, once it's running, it runs fine. The longer it sits, the harder it is to start.
Thanks

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Another question in reference to gmlent's comment. I do see that the boot on the fuel shut off solenoid it torn, will that cause a hard start condition?. How can I test the solenoid to see if it's working?
Thanks

 

The boot can come apart and get stuck around the rod causing it not to pull all the way in. so turn key on and reach in and push up on the rod, and see if it starts, my or my not be the problem.

 

Back to square one. I pressurized the tank to 15psi, no visable fuel leaks. I removed the fuel heater, still hard starts.

Question: When I pump the primer button, shouldn't it get harder to pump (it doesn't)?. Also, when I pump the primer, it almost sounds like air is being pumped out somewhere between the p-pump and the engine block (under the AFC)?. It's tough to see in there, but I don't think it's the return line, it appears to be fine. Is there anything between the p-pump and the block that could cause this sound when the primer is pumped?

 

bump

 

i would pay close attention to the fuel lines between the frame and the tank. thats were mine when bad at. the rest of the line was in decent shape. took me awhile to find the leak but i did..... replaced the lines with rubber and issue was resolved! hope this helps...also may wanna check your overflow valve... there cheap and will cause hard start when they go bad.

 

my step dads truck did this it would start after alot of cranking or alot of trys, get some contact cleaner ( i belive thats what he used) to help start it. he had a bad injector but his is also a 03' just an idea, or pull the injectors and have them tested

 

park it on the steepest hill you can find nose down overnight then see what happens when you start it the next day. if it starts fine then you definately have fuel bleeding back.