bobke20

i have read that the fuel overflow valve should be around $40. the dealer is the only one around that knows what the valve is and they want $160. if anyone can steer me in the right direction it would make me happy.

Tate

Cummins P/N 3941156 for the overflow, was $40.90 CDN. 3963988 is the part numbers for the sealing washers, need two, $5.19 ea. Have your engine S/N handy. They won't tell me anything without it.

bobke20

thanks for the help, orderd the part today

cbrxxtreme

What exactly is this overflow valve, where is it, and what does it do? I'm having a ton of problems getting my 97 twelve valve started (thread on "how to check injection pump") and this was suggested. Thank you for any input you can give.
Traver

Tate

Its a banjo bolt with a check valve in it, to keep internal pressure inside the IP, as well as to keep it from draining down when the engine isn't running. Thats what my problem was, causing hard starts after sitting for a half day or so. Its located on the front, just ahead of the fuel supply line on the VPs, and on the engine side of the p-pumps. It would also be a good idea to get a fuel pressure gauge on your truck. It sounds like the overflows have a tendancy to go bad on the 12Vs, and a fuel pressure gauge will help you pick up on that. If you pinch off the return line while the truck is running, and the fuel pressure goes up, then your OFV is bad. If it stays the same, then the likely culprit is the LP.

piperca

Not trying to be a smartarse, but it makes sense that when the return line is pinched, you'll get increased pressure ... correct me if I'm wrong.

Tate

From the 12v stuff, if you have a weak LP, pinching the return line won't get the pressure much higher than it is. If its the OFV, then it shoots way up.