low fuel pressure

I have a 96' blazer 2 dr. I am having trouble with it not wanting to start every once in a while it will usually sputter but has trouble firing. I checked fuel pressure and found that it is only at around 44 psi so i changed filter but no change. The check valve to check fuel pressure comes before the regulator to my understanding so I was wanting to ask if it was possible for the regulator to still affect fuel pressure at that point? I'm assuming it must be faulty but would like other oppinions. Btw when it does start, even after rough starting, it runs very smoothly with no problems and I can stop somewhere come back after a short time and it will start right up no problems.
Thanks, Wade

Small update I went out today to test fuel pressure with intent of checking while blocking the line to see if the pressure gets up to 70's or so to test pump but before so I checked regular pressure with engine off and it went up to 50psi this time. Im not sure if that means anything significant or not but I guess I'll know soon enough anyway.

ok more info, I just tested the pressure while blocking off the line just past the shrader valve and it only got up to 55psi. I am assuming that varifies a weak pump but I would like other oppinions to confirm before paying 200 bucks for a new one

You say 44 psi is low, what is spec for your application? If spec is 60 psi then I don't think 55 would be low enough to cause an issue.

One other test you should try is to prime the fuel rail several times and see if the pump is able to build pressure that way. On a Ford you would do this by turning the key to the run position, leaving it there for 3 seconds, then turn the key off for 10 seconds, then back to Run. Each time the fuel rail pressure should increase slightly, and the pressure should not drop noticeably between primes. If the pressure doesn't built past 55 psi and spec is 65 psi or higher, then the regulator is possibly the issue. If the pressure drops rapidly when the key is turned off, you have either a bad regulator, a stuck injector that isn't closing, or some other leak.

If the multiple primes allow the pressure to build to an acceptable pressure, then the fuel pump is likley weak. However there are other issues that could lead to long cranking before the engine starts. When was the last tune up performed (spark plugs, wires, air filter)?

-Rod

These trucks won't start with anything less than 60 psi. Check/replace the fuel pressure regulator located under the plastic intake plenum and on the back side of the injector spider assembly.

Also, clean up the poppet valves to help keep them from sticking and further preventing an easy start. They are notorious for sticking. There is a $250 upgrade from poppets to injectors...just letting you know your options. Good luck!

A diesel really needs a good fuel pressure!

Ok I've replaced the fuel pressure regulator but the first time I started it up it still started ruff and the pressure was at around 50 psi until it started then it jumped up and stayed around 60 shutting it down it dropped quickly to around 20psi I don't know if that is supposed to happen or not. As usual though it started right up after and fully pressurized.

You may have had excess fuel in the intake and cylinders from trying to start it prior to the fix and/or from any leftover carb cleaner.

After the pump shuts off after the initial key-on, it should maintain pressure for 5-10 minutes. Fuel pressure that continues to fall is caused by one of the following items:

-The in-tank modular fuel sender is not holding pressure.
-The fuel pressure regulator valve is leaking.
-A Central SFI injector is leaking.
-Fuel line is leaking

I don't recall if it maintains pressure in the lines after key-off though, but common sense tells me no...anyone? At least it runs again! Congrats!