97 blazer fuel pressure

[Sunliner]

I'm trying to run down some starting problems on my 97 Blazer.

Checked fuel pressure at the port under the hood. Here's what I got:
Key "On" 54
Engine running 52

As soon as I shut the engine down, the pressure immediately dropped to 48.

With that info, is it possible to tell if it's the pressure regulator or the pump?

[old_master]

To answer your question... no.

Key on, engine cold and off, fuel pump running, fuel pressure must be 60psi to 66psi and must remain above 55psi for 3 to 5 minutes after the fuel pump shuts off. Post your results doing it this way and we can help you with diagnosis.

[Sunliner]

I'm not trying to sound smart, but I thought that's what I did ? This is my first time checking this, so maybe I did do it wrong.

When I first turned the key on (engine off), the fuel pressure was 58 psi for a few seconds, then leveled out at 54
The engine wasn't completely cold but had been shut down about 30-40 minutes before I hooked the gauge up.
When I started the engine up, it dropped to about 52 and stayed there until I turned it off, then it immediately dropped down into the 40's.

I appreciate the help!
-Mike

[old_master]

Ok, I understand, I just wanted to make sure on your procedure.

Key on pressure of 54psi is too low, your leakdown of approx 6psi is understandable and is acceptable provided it doesn't continue to drop. The reason it's below 55psi is due to the pump not building enough pressure. To determine if the problem is the pump, or something in the plenum, the pump needs to be isolated from the plenum just after it builds pressure. To accomplish that, there needs to be a shut off valve installed either permanantly or temporarily, between the pump and the plenum. Check your inbox for a PM, it explains how to do it.

[ski332]

I have a 98 and getting same problem-- key on it goes to around 63 psi for a second then immeditly drops to 56 and stays their with key off--- Truck will run for about 1-3 seconds

[paulmagee]

hello as i am having the same problem could you send me the same thread so i can try that thank you in advance

[old_master]

Originally Posted by ski332

I have a 98 and getting same problem-- key on it goes to around 63 psi for a second then immeditly drops to 56 and stays their with key off--- Truck will run for about 1-3 seconds

Your fuel pressure and leakdown results are fine. Leave the pressure tester connected and watch the pressure when you start it. If pressure drops off and then the engine stalls, it could be a problem with the ECM not receiving a signal from the crankshaft position sensor, or the VTD, (Vehicle Theft Deterent) system is disabling the fuel pump relay. Either way, you'll need a scan tool capable of watching those circuits. A typical code reader like the auto parts stores use will not do the job.

[serpentracer]

it's usually fuel injectors that leak down.
everyone blames the pump.

52 psi while running is a little bit low for a 4.3 it should be closer to 55-60. and about 62 key on engine off.