Well i've been following the overflow valve thread on here because i was getting about 14PSI at idle(750RPM) and about 22PSI at 2500RPM. so i ordered an overflow valve from the guy on ebay. When i got it i put it in and was getting 18PSI at idle and 27-32PSI at 2500RPM. i was estatic and looking forward to many days of happy motering. but after about 4 days of good pressure i'm down to 10PSI at idle and only 13 at 2500rpm. What gives? the truck has 195,000 miles on her and i've owned her for the past 30,000 and dont know weather i'm still running the original lift pump or not. i'm gonna put the old overflow back in when i get a chance and see what my pressure is. does this sound like the lift pump on its way out? or has any one else had this happen when they installed their new overflow valve?
thanks for your time

 

It could be either the new valve or the lift pump. Swapping the old valve back may tell you, I've also had good luck by pinching off the return hose behind the injector pump with needlenose pliers, to see if the pressure rises.

 

I purchased one from the guy on ebay also. Figured id do a good thing and just replace it sinse its 14 years old. No good deed goes unpunished.......If it aint broke dont mess with it and so on and so on. I noticed lower fuel pressure right off the bat. At idle its running 21 psi (was 26 or so) and down the freeway i'm right at 20psi was at 28, was 32 at at 2k no load now its 24. gonna put my old one back in. I am going to contact him and see if maybe its spec'd for something else?

 

I also purchased one from him last thursday and supposed to be here tomorrow, I sure hope it isn't a bad one!! You will have to keep us update on how your contact with him goes and I will install mine tomorrow night and let you know how mine is.

 

I bought a new one from Cummins a few years back that caused the same thing, low fuel pressure.
They gave me a new one no questions asked, they didn't even want the old one back.
Hopefully the ebay guy will do the same.

 

Just wondering if this maybe associated to a bad run of overflow's. I bought mine from Ebay guy during the period shown in the link below. Haven't installed it yet.

http://cgi.ebay.com/ebaymotors/ws/eB...m=250425345078

Auction end date was May 17th.
Item Number was: 250425345078

Maybe we can pinpoint it to the group of 6 that he had listed. Just a thought.

 

well guys just put my old one back in and the fuel pressure is even lower 8 at idle 13 at 2500rpm. looks like the new valve put to much strain on my old lift pump. i'm gonna try pinching off the return line and see what my pressure does. i had good pressure with the new valve for a few days and when i pulled it out the spring still appeared good and looked like it was holding the check ball securely. so i think it was a good valve. i'm not going to bug the ebay guy till i make sure its not my lift pump. i'll keep you guys posted

 

Buzz..;
Sounds as you do have a weak lift pump. Luckily, the price has dropped well below $100 Be carefull to soak the fitting on the line that goes to the filter. It builds with gunk and will twist the line.

Pressure versus flow.
Static (truck not moving or running on a dyno) pressure tests may give false readings. A weak lift pump that cannot make the proper flow required to feed the injection pump can still give OK pressure on static tests.

 

fueling can you please tell me where i can find one for less than $100. Are there any sealing washers or the like that i need to get before i tear it all apart

 

Your local Cummins store.
I'm not sure if the Case-IH-NH dealers have come down below $100. They used to be a low cost scource.

 

Cummins dealers reduced the price of our lift pumps to $79 for some reason about a year ago.
My thought is they're trying to reduce the stock of parts for old engines.

 

alright thanks guys i'll check them out tomorrow