95 C1500 fuel pressure

[ZVar]

Can I verify the pressure on a 1995 C1500 1/2 ton?

It's a TBI with a 350 (5.7l) gas engine.

 

I tested the pressure and it's showing between 10-12 PSI.  About 12 at idle dropping to 10-11 on the road test.

I tested before the fuel filter if that matters.  The filter is new.

 

I did the pressure test as the symptoms are...

1. This is all very random, but getting more common.

2. On a 12 mile commute to work it will stall at least once.  Most of the time more.

3. Starting to loose power on the expressway, starting to happen once a day, so either going to work or coming home.

 

If the pressure is fine, what else should I look for other than the pump?  I did try and find vacuum leaks with none found.

[Doug_Scott]

I'm thinking you are lucky to get the truck up to highway speeds with fuel pressure that low.  Are you sure you are testing it correctly?  You should be testing at the Schrader valve on fuel line.  I do not recall if your engine has the vacuum controlled fuel return line, but if it does try blocking the fuel return line and see what pressure you get.   EFI has always been upwards of 50 to 60 psi over all the various systems from the different car companies, so 12psi is not normal.

[ZVar]

Are you sure about that?  I ask as I'm finding anything from 8 to 15 PSI for a TBI system.  The multiport starting on the 1996 models require 50-60, but not the throttle body in 1995.

[Jsdirt]

Those pressures are fine for TBI.

 

If the injectors are good, wiring good (not randomly losing injector pulse), then I'd be checking out the ignition for problems. Symptoms fit a failing ignition module, or pickup coil, or ignition coil.

[Doug_Scott]

3 hours ago, ZVar said:

Are you sure about that?  I ask as I'm finding anything from 8 to 15 PSI for a TBI system.  The multiport starting on the 1996 models require 50-60, but not the throttle body in 1995.

Sorry, misread the type of injection. 

[JD110]

Check distributor shaft, the magnets are cracked. Replace shaft and pick up coil. This causes a lot of stalling and drivability problems.

[GTOlives]

As I have had three of these one with well over 300k miles multiple fuel pumps. The best top pressure you want is 18psi 11 to 15psi measured before filter normal operation. you put a high above 18 on this it freezes up. He's talking about later efi with the shrader relief different design. I see the consistant above 11 psi on freeway speeds or if I punch it for higher speeds, startup. Basic 101 design you are either over fueling (Going) or under fueling slowing. One thing for sure your pump is ageing just like us, this certainly is one of your problems. I had 5 pumps in mine to date and will put a 6th one it when pressure drops as yours and mine has. Good MTX pays off, these engines are great maintained I've not changed the chain and the electronics keeps it massaged as new. Not that I wouldn't fine wear on it. I plan on 500k miles and change oil regularly with full lube. Most cars don't die if you maintain them, you kill them! The Grasshopper