hey folks, been perusing the archived thread for a month or so now, & had a question. my 95 has lost prime because it sat for a month or so, & when I manually pump the LP it doesn't feel like theres any pressure when the fuel filter gets full (On my 94 it still does like normal). I replaced the fuel filter & while it was off, I pumped the manual button on the LP & fuel came squirting out each time. Would it possibly be a bad O-ring thats making squirt, but not enough to feel 'normal' when the filter is on? trying to not have to take it to a mechanic tomorrow-thanks

 

shouldnt feel like a lot of pressure do to return lines. their is a rubber hose behind the injector pump some times it gets rotten and allows the it to lose prime but it wont leak. took me about a week of searching till i found it

 

when it loses prime did u losen the bleeder screw in top of the fuel filter base? if so were u geting bubbles or steady fuel?

 

Could be the spring on your bypass valve is weak.

 

I had a similar problem and it was the bypass spring in the overflow return valve. You can stretch your original and see if that fixes the problem or not. If it does you can drive on the stretched original while waiting for the new one to arrive.
Olin

 

When this happened to me I had leaky fuel lines running from the tank up to the pump.

Make sure those aren't leaking

 

I had to eventually change the fuel lines on mine too. Checking the spring is a much easier fix if that's the problem. Start simple.

 

Testing is always the best way to find & fix .
Fuel pressure test .
It could be about 6 different things , it would cost too much to just replace everything .
If the pressure is low , pinching the return hose [ with gauge hooked up ] , if the pressure comes up , then it likely the OVF overflow valve .
If not then it could be the LP lift pump .
I have done both , now have the same issue again , and figure this time it may be the pickup in the tank , because it starts normal above a 3rd of a tank .

 

Look at Joe G's write up. A lot of good info.

http://www.cumminsforum.com/forum/94...m-writeup.html

 

I opened the bleeder, & it trickled some bubbles sporadically, but still feel no 'pressure' when pumping the LP bulb manually. Its like there's an air leak keeping it from building pressure.... I can't use a fuel ppsi gauge yet, cuz I can't get it started..........

 

checking the overflow byp. spring next....

 

well the spring was broken & about 1/8" shorter than normal-gettin a new spring now..... can't believe they make ths stuff so cramped you can BARELY get hands in, let alone get the nuts & bolts squeezed in & out

 

anyone know the part# of the tapered spring? my local cummins dealer doesn't have stuff for the 5.9- durrrr..............................I may have to go to napa

 

Don't believe you can buy just teh spring for the overflow, get a new overflow valve, Fleabay usually has them for 30 bucks or so.

 

Some people use a spring from a Bic pen but I think it's a lame idea.
Search on ebay for Cummins overflow valve where you can buy an OEM valve for $30.
His shipping is very fast.