Hey guys. Forgot I belonged to this forum but glad I found it again. I have a 2002 Chevrolet Blazer 4 door, 2WD 4.3L that I suspect has a bad fuel pump or fuel pressure regulator. I had an old a/c low pressure gauge lying around and with the right adapter I was able to test the fuel pressure. Turning the key on it went to about 43 psi and within 3-5 seconds dropped to 0. I read somewhere that the drop is normal (a safety feature) but should it drop that fast. My understanding is that fuel pressure should be a minimum of 50 to 60 psi. Looking to confirm that here. Also besides the fuel pump and the fuel pressure regulator are there any other components I should consider replacing for good fuel delivery?

I don't see much for vacuum hoses but I did find one 7/32" one from the top of the engine (intake/valve cover area) going over to the corner near the driver and it was coming apart so I replaced it with one I had on hand (5/32"). Directly in front of the driver was a "T" fitting the one end connected to a rubber fitting leading to a smaller hose/tube following down the firewall, the third leg of the "T" had a hose leading back towards the front over the wheel well but didn't connect to anything and I can't see anywhere that it would have connected to. Any ideas?

I have my dads OBDII tester on loan and it had a code for C0265 (Electronic Brake Control Module Motor Relay Circut).

Any help, ideas or input is greatly appreciated.

 

The mystery hose likely goes to a vacuum reservoir in the fender. Check out my vacuum hose thread in my signature.

 

I had a hard time finding that one also. If you run your fingers back there you can feel the nipple, there is a small vacuum tank mounted in the inside of the fender area. I pulled the bolts out of the ASB controller and pulled it away to see. You don't want to do that.

 

Lowest I've seen with a good fuel system is 58 psi with the key on - then a drop to about 53 psi after a couple of seconds where it should hold for a while. If it doesn't hold, then either the fuel pressure regulator or the check valve in fuel pump is the culprit. There is a sticky at the top of the second gen forum about fuel pressure testing/diagnosis. However, I don't agree with the necessity for 60 psi, especially when you have the MPFI injector upgrade (AC Delco). I've seen too many regulated to 58 psi. Fuel pump itself should be able to put out far above 60 psi in any case - it's just regulated down. There are procedures to definitely test the fuel system described.

The vacuum reservoir is mounted inside the rear part of the drivers side fender, accessed from the engine compartment. Need a mirror or to stand on your head to see it.