eng208

Well, I drove my truck today and it would not pull past 2000 rpm. The top speed was 74 mph. I couldn't build more than 20 lbs of boost and the truck would sputter at 2000 rpm. Also, it would not accelerate at all on a hill, and it cut off 3 times when I came to a stop. I checked the lift pump and now I am not getting any squirting sound from the overflow valve when I pump it. The truck has 86K miles on it. Do I need a lift pump, and how much are they?
Chris

marksmith

Id look at the O/F valve itself before you get too carried away.


If you take it off and pull it apart (careful not to lose the shims, spring or ball) You can stretch the spring 1/4 inch or so. Put it back together and see if it helps your cause.

If it is, order another one from Piers.

If it doesn't help your cause.... dive deeper. Get a F/P gauge on it to see what pressures you are running.

eng208

Just talked to the shop. They put gauges on the truck, and the input fuel pressure from the lift pump to the IP is 10 psi. They replaced the O/F valve and are going to check it again sometime today. The boss is working on it. I hope he takes care of my truck.
Chris

Dave88LX

What was hit? I'm having similar issues.

plow

It sounds like a bad overflow valve, if pressure is lower than 17 at idle a way to check is pinch the return line with pliers and see if pressure climbs if it does replace overflow valve the liftpump is good, if the pressure doesn't climb replace the liftpump. 17to22psi at idle, 25psi min. at 2500 rpm no load.

Dave88LX

What will it do if it's neither?

eng208

He replaced the overflow valve and the prefilter screen on the heater just beside the lift pump. Fixed it.
Chris