Starting issues Our 1999 GMC Jimmy will not start. The fuel pump and fuel pump relay is working and the fuel filter has been replaced. It will crank but will not start. Last week we had a code reader on it and it gave us a few codes, one of them being the crank shaft positioning sensor. Could it keep the truck from starting?

Is your fuel pump relay getting a signal? Is it any good. I would start by figuring out why the pump isn't running

Kelly, could be a few issues, security lock out, crank sensor, fuel pump fuse/relay, faulty new pump,faulty ignition switch, etc. Attached links may help you diagnose the crank no start issue you are having.
Check the attached links,video,instruction and guides, Good luck
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you might have to replace the fuel pump as the small plastic gears need fuel to lubricate them and with out fuel they tend to mess up bad.

Yes. Replace this sensor.

Spray some starting fluid, (ether), directly into the throttle body. Does it start with that?

This might apply .. but it for a 1999 Jimmy:
Electronic Fuel Pump Computer Problem6 Cyl Four Wheel Drive

Your symptoms could also be do to other issues ... not just the fuel pump relay. Read the embedded link within the 2carpros response.

Good luck with your troubleshooting

yea you have no fuel and sound like a bad harness and the gm's are know for there fuel pump harness's! did you change it when you changed the pump? there is a lose connection somewhere in the fuel delivery system and it's pretty simply! i would check the fuel pump relay on the left hand side of the engine compartment and maybe even put power to the pump at the relay position "b" on the fuel pump relay harness and there should be a one pin connector to put power to also connected to the same position on the relay "b" the wire should be tan and white! good luck

Replace the fuel filter before the pump goes bad, just paid $700 to replace OEM withan aftermarket fuel pump and filter (better than $900 quoted by another shop. Had I changed the filter sooner, may have avoided. Now dealing with a bad intake mfld gsked and old leaking oil cooler lines. Help, GM is killing me!! These vehicles are notorious for various issues.

Good luck

The pressure relief valve is in the spider fuel injector not the fuel pump. We have had our 94 gmc jimmy for 4 years & have had to replace the fuel injector 4 times which cost right at $500 each time for the part. Yes the spider fuel injector cost averages around $500.

I'm not sure of vin? My info shows oil pressure switch in parallel with fuel pump relay, so if that switch is functional and has voltage, once you crank it enough to bring up oil pressure, the pump should run even without the relay. The voltage for load side of relay and oil pressure switch comes from ecm B fuse. The voltage for control side of fuel pump relay comes from pcm.
Any other issues besides fuel? Engine cranking do you have spark at the plugs and fuel injector pulse? If your missing the last two, have to check for rpm signal.