Fuel pressure
 

1996 s10 4.3L "x" v6 5speed 160k miles

So, my truck has always had a very very slight hesitation from time to time at idle that hasn't ever affected my driving. The last few days it has started to hesitate in 1st gear randomly. Not much but noticable. Also it has started taking a couple extra seconds to start after cranking. Usually when cold.

My fuel pump has always had a whine to it so I thought maybe it's finally going out. Today I got a fuel pressure gauge to check it out.

Here's what I got:
It cranked and idled at 54psi.

When i shut it off, it immediately dropped to 50 psi and held for about 30 seconds before it slowly went down.

After being off for 2 minutes it was at 42psi.

3 minutes: 40psi, 4-5 min: 38psi. 7 min 36psi. 9-10 min: 34psi.

According to these 2 how to articles....

http://troubleshootmyvehicle.com/gm_fuel_pump_4.3L_5.0L_5.7L/fuel_pump_test_1.php


http://troubleshootmyvehicle.com/gmc/eight-cylinder/198-testing-the-spider-fuel-injector

....it sounds like I have either a pressure regulator leak or an injector leaking. Apparently it should of held at 40-45 psi for 5 min. But the article also expects it to drop to 0 psi pretty fast after shuttting off the engine if it's leaking, which mine didn't do.

I work out of town so I'm just doing some research untill I can look inside of it in a couple weeks.

What do you guys think?

I had a noisy fuel pump on my truck at one time and was losing pressure pretty fast after killing it. Turned out to be the fuel tubes going through the top of the fuel pump holder had work themselves loose and air was being sucked in continously to keep up.

The fuel pump has a check valve in it to keep fuel from bleeding back into the tank. This could be bad and causing your problem. You can either replace the fuel pump or add a check valve in the fuel line like I did. Solved my problem and cheaply.

I went ahead and replaced the fuel pump. Seems to be working well so far. I've only driven around town a little bit.