I have a 1997 Dodge 3500 ram Diesel. It has very little fuel pressure. I have Check the filter in the tank. I have changed the pre filter and the fuel filter and have checked all the fuel lines all are good. I have change the lift pump.
I also checked the over flow valve by pinching off the return line.
I put a test gauge at the inlet line at the injector pump. it is only getting 5psi of pressure.
Could the cam lobe that drives the pump be worn????
John

 

Pull your over flow valve off the engine, take it to a vise, and remove the small bolt on the top of it. There is shims, a spring and a ball inside. Careful not to lose the shims. Get a retractable click pen, and take the spring out of it. Cut the pen spring to the same length as the original spring inside the OFV. Reassemble with both springs and the shims, and reinstall on the pump. If you want more pressure than what you have now, you can stretch the springs a bit, or take the remainder of the pen spring, cut it a bit longer, and use it with the stock spring. I just kept the spring lengths the same, and I went from 14psi to 40 psi.

 

No need to remove the overflow valve if you pinched the return line and the pressure didn't increase, the problem is the lift pump.
Sometimes even new ones can be bad.

 

FWIW worth, I tried pinching the return line on my truck when I was troubleshooting, and no difference. I figured I'd try the OFV trick before replacing the pump since its a whole lot easier. My truck also doesn't have a pressure rise from idle to 2500 rpm, which seems odd.

 

Other than low PSI, how does the truck run? Maybe you have a bad gauge.

 

Yes the truck runs at low speeds put will die when you push it. I tried two test gauges both read the same.

 

I put a inline electric fuel pump in the system which held at 12psi at idel when you got in to it it would loose the fuel pressure and die

 

If that's the case I'd start looking for a clogged filter (three of them) or a kinked hose/line.
Perhaps pushing some compressed air backwards though the feed line on the tank side of the lift pump will tell you something or unplug any obstruction.
Remember to remove the fill cap.

Make sure the fuel shutdown solenoid is lifting all the way. Sometimes if they're full of crud from a torn boot it will feel like it's lifting all the way but it's really not.

 

Bill
I did all of the filters and lines. I clean the screen in the prefliter I think it might have some junk in it above the screen. The shutdown solenoid is new put I checked it to.

john

 

Have you checked the fine mesh screen on the input of the lift pump? Thats what was blocked when I had very low FP.

Gaza

 

No The lift pump is new put I will check it again

John