1993 GMC Jimmy 4.3 vortec auto 4x4
OK, It started 3 days ago... not having any pick up like it was outa gas. Then it started stalling, again like it was out of gas. I thought it might be a fuel filter, so I changed that and it's still the same... when I try to start it, it only fires for a second.
I suspect the fuel pump next. When I turn the key I can hear it for a couple seconds, so I kknow it's working.... is there a way that the fuel pump might be not pushing hard enough? how can I test it without a pressure guage. Thanks

 

You really need a fuel pressure gauge to check for the proper output from the pump. They aren't that expensive.

 

ok, looks like I'll have to get a guage.... can I test it where the fuel filter is? or do I need to figure out where to put it on the engine?

 

Do you have the CPI or TBI motor? The CPI has a large aluminum upper plenum with a 'VORTEC' in orange letters in the middle while the TBI has a traditional round air cleaner.

If you have the TBI fuel system, then you will need an adapter to put the gauge inline with the fuel feed. For the TBI system, proper fuel pressure is in the 12-18psi range.

On the CPI motor, there will be a fuel pressure test port on the back of the intake manifold where the fuel lines enter the plenum. No additional adapter necessary. For the CPI motor, you should see 55-60 psi of pressure for proper operation.

 

I have the first one you mentioned, with the vortec deal and aluminum intake.... hope it's not too hard to find it.... anyone got a pic?

 

On the CPI motor, the fuel pressure test port is located on the back, driver's side of the plenum. Look directly off the back side of the intake near the brake booster. You should find a cap on the test port. The test port is basically like a tire valve, but a bit larger.

 

borroweda tester and it reads 60 psi..... still acting excatly the same...... will attempt to fire, but only for a second after the truck has sat for awhile.... any ideas what to check next? I can't afford to have it towed o a shop. BTW the service engine soon light comes on at stop lights and then goes off.... also comes on after 5-10 min of high speed driving..... HELP!

 

Probably is not the pump, with that kind of pressure reading. Did you not stop at a place like AutoZone and have them read the codes from you SES light? That info can tell a lot about where to start looking for a cause. It could be a fuel pressure regulator, bad injector spider, etc.

 

What does the pressure do when you turn the key off? Does it hold at 60psi? Drop off fast?

 

when I turn the key it spikes and stays there @60 PSI when I turn the key off.... at least for a few seconds.... but I do not know how long it will hold that