pizon6979

Hey Guys, I'm new to this forum thaught I would see if some one could help. I have a '96 blazer w/ 4.3 v6 4x4. It wont start, It turns over fine, when I spray a little starting fluid in the intake it starts up ok and runs fine. until I shut it off and it wont start again w/o fluid. I changed the cap/rotor, plugs, wires and fuel fiter. and still no change. I checked the fuel pressure and was good (around 60psi) didn't bleed right off or any thing. I have know ideas, why would it start and run with starting fluid but not by its self? any help would be great!! Thanks -Tony

old_master

You have a fuel pressure problem here's how to test it:

Fuel pressure test:
This determines if the fuel pump is capable of building adequate pressure to satisfy the fuel pressure regulator. It will also determine if the system is able to hold the fuel pressure. If the pressure is insufficient, or the pressure does not hold, this test does not determine what the problem is. It only confirms that a problem exists. Fuel pressure must be tested only when the engine is cold. This avoids increases in pressure by heat radiating from the engine causing erroneous readings. GM does not publish engine running fuel pressure specifications in the “dealer issue” shop manual. Make sure the fuel filter is not clogged with dirt before testing fuel pressure, easiest and best just to replace it. Here is a link to an adequate, inexpensive, fuel pressure tester: http://www.harborfreight.com/cpi/cta...emnumber=92699 Install the fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After 2 to 3 seconds, the fuel pump will shut off and the fuel pressure must remain above 55psi for 3 to 5 minutes. A drop in pressure below 55psi indicates excessive leak down.

pizon6979

Thank you for your response, but as I said in the original post I checked the fuel pressure and it seems ok, also I replaced the fuel filter already. Any other ideas? thanks for your input! -Tony

pizon6979

I will check the fuel pressure again tomarrow. Maybe I am doing it wrong. I'll let you know how I make out. thanks again!

old_master

What you described is a classic symptom of low fuel pressure, "around 60psi" is borderline. It must be a minimum of 60psi. Check it with another gauge, you'll find a problem.

pizon6979

Hello, I finally got around to checking the fuel pressure. I checked it with a different gauge. I turn the key the pump goes on and only pumps up to 30psi. It holds at 30psi for at least an hour or so. So far I've changed the tank, and rear fuel lines, (they where leaking) but still no difference in psi. Any Ideas? Thanks and merry Chrstmas!!! -Tony

old_master

Fuel pressure is too low, must be 60 to 66psi. The fact that the pressure holds, indicates that the lines, injectors, and pressure regulator, (all under the plenum) are more than likely ok, and that the fuel pump is weak. Check pump output by installing a fused jumper wire to the pump feed wire, slowly restrict the return line while watching fuel pressure, do not allow it to rise above 75psi. If pressure will not reach 75psi, the pump is weak and will need replacement.

pizon6979

hello, I just wanted to thank you for all your help!!! I replaced the fuel pump and it seems to work fine. Thanks again and God bless!!!! -Tony

old_master

Good job! What are the readings with the new pump?

pizon6979

The pressure is right around 66psi and holds when turned off for about 10 mins. the bleeds off slowly. thanks alot!!

old_master

66psi, that's great, what brand of regulator is that? Most of them I see are around 62 or 63psi.

pizon6979

It is an Airtex, I have heard a couple people on here say there no good but it is the only one I could find that is made in the USA. and I got it on ebay brand new for $135. I'd say you can't beat that.

old_master

Airtex is the pump, have you replaced the regulator or is it OEM? I have used Airtex pumps for years, several of them already have more miles than the original OEM pumps got. I always upgrade the connector at the pump and add a 14 gauge ground wire from the connector to the body of the vehicle. Along with replacing the fuel filter every 5,000 miles, that might have something to do with improving the longevity of the pump.

pizon6979

The regulator is stock. I will have to try the up grade on the wiring sounds like a good idea.