A fuel pressure test at the Schrader valve with the Autozone loaner pressure tester shows zero pressure. I turned on the fuel pump a few times with the key turned to accessory. I can hear the fuel pump come on for 2 seconds. The pressure gauge needle never moved off zero at all. Then I started the vehicle. It always starts and runs, although not very smoothly and accelerates with hesitation. The fuel pressure gauge shows zero pressure with the Blazer running. This raised my suspicions about the gauge, so I turned on the fuel pump again several times with the key turned to "accessory". Then I manually pushed in the pin in the Schrader fuel test port. No fuel came out. Then I started the vehicle and pushed in the pin with the vehicle running. Some fuel came out, but it was not under any significant pressure.

I am guessing based on reading the fuel pressure articles on this forum that I have a leaking fuel injector, leaking fuel pressure regulator or bad fuel check valve in the fuel tank. Is there a definitive test I can run to determine if I should be opening the plenum or the fuel tank?

 

Sounds like your test port is bad. If it's starting you most likely have over 50 pounds of pressure. I've replaced schrader valves in A/C systems but never the fuel port but I assume it's a similar process. You can't do proper diagnosis until you know the fuel pressure. If the fuel pressure is up to par then you can start looking at the FPR and spider assembly.

 

No way your truck would start with a reading of zero. The gage is bad, the shrader is f't up your having trouble with the threads on the gage. If it was treads on the gage I would think you would smell raw gas.
You need to be a little carful over there due to the proximity to the distributor.
Set my entire motor on fire one time.
Make sure you have at least a 10lb extingsusure on hand and a hose three one lb boxes of baking soda.


This is what you need.


http://www.dieselorings.com/schrader...-1-8-mnpt.html


Viton seal is the main thing, it's the same thing as a tire gage seal, all you really need is the stem. The Viton seal is the main thing. The rubber ones on a air seal will melt.


Think the company that makes them is in Connecticut but you have to buy something like 500.

 

Thanks Dobyken and Spittybays. I didn't know Schrader valves failed, but now it is a suspect. I recently replaced the intake manifold gasket and may have gotten some fuel rail o-ring pieces in the Schrader valve. I noticed when I removed the injector feed tubes that the old o-rings were mangled. They were replaced of course. I'll take off the injector feed tubes and check the Schrader valve. I don't think my Schrader valve is replaceable though. It is welded into the injector feed tube.

 

No the "Hub" of the valve is locked in. The valve itself screws in like a little screw in plug.


Look up bicycle Schrader, or tier valve, its the same thing just made to not melt with gas

 

Those loaner fuel pressure testers are not to be trusted at all !!!!