Engine/Transmission (1994 - 1998) Fuel Pressure Question

[EKlem]

When I started up my truck the other day, the fuel pressure gauge read 8psi or so rather than the usual 30+. The next time I started it, it showed no fuel pressure and after a couple of miles of driving, it had come up to 3psi. It still shows 0 on startup and moves up to about 3psi.



I really don't think that the gauge is right. The truck is running fine and it still pulls loads normally. As a check, I felt the fuel line between the lift pump and fuel heater and you can really feel it pulsing as normal. I also pinched off the return line to see if the fuel pressure would go up and it did not. With the truck off, I pumped the primer by hand and I could hear the overflow valve which means that fuel is flowing. The only two things that I can think of having gone wrong if it really is low fuel pressure is a really bad load of fuel(this happened ~40 miles after filling up) or the overflow valve has ceased to work.



I am guessing that I have a problem with the gauge setup somewhere. It is an isspro setup with a snubber, isolator, and 60psi gauge. The 60psi gauge has only been on there for about a month. I tried putting the old 30 pound gauge back in since it still works fine and it showed the same thing the 60 had shown. Is it possible that either the snubber or the isolator is bad? I was thinking that I could bypass the isolator with a few brass adaptors and check that. Any other suggestions?

 

[Missouri Mule]

Try putting a hand held mechanical pressure gauge on it. See what it reads.

 

[EKlem]

To follow up, I determined the cause to be a failed isolator. I noticed that when I hooked up the new gauge a few weeks ago, there must have been a leak in the connection since there was a little bit of antifreeze that leaked out. This leak probably lead to the failure of the isolator. I now have a new isolator and replaced the compression fittings on either end.