kawi600

I got this truck last year and replaced the lift pump (cummins OEM pump). The filter and screen are recently changed. I did the overflow valve directly from cummins and my fuel pressure looked a bit high. Was 35psi at 2000rpm no load.
Recently the pressure has need dropping and even fluctuating at idle. I put a test gauge on there and checked the measurement and it was 25psi at idle, 25psi 2000rpm no load, which shot up when I pinched the return line.
I could try stretching the spring back out, but I dont like the idea of causing the spring to fatigue and break.
So Im guessing I need a new overflow valve. How long do these things last and what could be killing them so fast? I wonder if I should try to source some kinda of heavy-duty regulator and install it inline.

infidel

Luck of the draw maybe?
Both my trucks have a in cab FP gauge.

3500 is still on the original OF valve with 212k.

My stock OF valve on the 2500 went out at about 80k, the replacement has been in there for 140k. Current valve is from
Precision Diesel Injection and Turbo Inc.
Marty Tompkins
888-734-7349
$40 + $7 shipping and handling.

kawi600

hm, its not the overflow like I thought. I bought another from cummins northeast and the pressure is even lower than before. 22psi at idle, 25 at 2000rpm no load. Im thinking I have a line restriction or air leak someplace in there since the pressure dips to 10psi with my foot in it
The pressure problem pre-dated my veggie oil conversion so Im thinking its the stock fuel lines. Ill know once I purge the air from my aux fuel system and run diesel from that.
Good opportunity to upgrade to 3/8" aluminum tubing for feed and return! mcmaster-carr must love me by now