I went to start my 93 trans am lt1 this morning started right up then died 5 minutes later.Then it wouldnt start back up so i put gas in it finally started back up and died again i think the fuel pump is going bad does anybody know what pressure it should have? im also going to try some dry gas it has been sitting for about 45 days.
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93 trans am lt1 soon to be a 406 gen 1 sbc all bolt ons zr1 wheels dr in back built 700 r4. -
When you turn the key to on, the fuel pump should prime for about 2 seconds, then shut off. Fuel pressure should be at least 40psi. Then watch to see how fast the pressure bleeds down. Should drop very slowly. If it drops fast, could be leaky injectors, faulty diaphragm in the fuel pressure regulator, or a bad check valve in the fuel pump. If it drops, priming it several times in a row should build enough pressure to let it start. If it appears flooded, put the accel pedal on the floor and hold it there while you crank it. That puts the ECM in "clear flood" mode.
If you get it running, at idle, vacuum compensation line off the fuel pressure regulator, pressure spec is 43.5psi. Anything between 41-47psi is OK. When you reattach the vacuum line, pressure should drop 6 to 8 psi, with a stock cam (less drop with a more radical cam). At that point, its out on the road, max RPM max power and the fuel pressure should stay at the "no vacuum" pressure.Fred
381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor -
the pump is not priming everytime i turn the key only about half the time that is why im thinking it is the pump.93 trans am lt1 soon to be a 406 gen 1 sbc all bolt ons zr1 wheels dr in back built 700 r4.Comment
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Did you test the pump by connecting 12V power directly to the "fuel pump prime connector", up by the PCM? That allows you to bypass the PCM control and the relay to make sure the pump is operating correctly. Is a small gray single pin connector, loose, in a bundle near the PCM.Fred
381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motorComment
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no i didnt can you please tell me how to do this and what to look for93 trans am lt1 soon to be a 406 gen 1 sbc all bolt ons zr1 wheels dr in back built 700 r4.Comment
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Connect a wire from the red terminal box near the battery, to the gray fuel pump prime connector near the PCM. If the pump starts and runs, it is OK. The problem would be in the relay. If the pump doesn't run, you know its the pump or wiring to the pump.
If the pump does run, check the fuel pressure by connecting a fuel pressure test gauge to the Schrader valve connection behind the passenger side fuel rail. If you get that far, I can tell you what the pressure should be.
Courtesy of Shoebox:
Fuel Pump Test Connector:
Schrader valve connection:
Fred
381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motorComment
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