Fuel Pressure problem or Guage?

[BarlowCummins]

I think that I may have a fuel pressure gauge problem. My gauge is reading zero right now but the truck runs fine and has plenty of power. The needle on the gauge will sit at 8-9 psi when working properly. This is the second time the gauge has done this. The needle will slowly fall to zero and the light for the needle will stay at 4 psi. This happened to me on vacation last month and after sitting for a few days the gauge started working again. Now it dropped again to zero last night. Could it be fuel pressure problem or just the gauge?



Thanks

 

[JLandry]

If it's a mechanical fuel gauge, you may have a leak (and now possibly air) in the line running between the isolator to the gauge. You'll have to purge the air from the line and insure the rubber diaphragm inside the isolator is centered again. The diaphragm will become uncentered when fuel pressure pushes it toward the gauge side as anti-freeze leaks from the line between the isolator and gauge.



Another common cause of inaccurate or low mechanical fuel pressure gauge readings is a kink somewhere in the line between the isolator and gauge.



If it's an electric fuel pressure gauge, then it could be a problem with the sender, wiring, or gauge.



Good luck.



John

 

[CKelley1]

if it is a mechanical with an isolator. remove the isolator and all tubing. get a oil pressure gauge installation kit. it has all of the fittings and 6 feet of copper line. the reason for scraping the tubing is a lot of them used antifreeze instead of glycerine, the instruction sheets were vague and the person did not properly charge it. there is a piston or diaphram that forces the gauge liquid if you do not set the piston back it is at the end of its stroke and can not compress any thing for the gauge to read . and when a properly charged one fails it allows water antifreeze to migrate down towards the cp3, the idiot that thought this one up should be shot. if it is electrical use the kit and mount it vertical near the clutch master cylinder, leave the excess tubing coiled up. if it was bad this will not fix it but will stop from ruining a new one. you do not have to bleed either one and in fact they will work better if you do not. lastly i have seen a pump do this. the best way to trouble shoot is to get the kit and install the line and place any 15 psi gauge on it and drive it.