Cranks, but fuel pump won't turn on

uluz2a6

uluz2a6

Senior Member
2003 Pontiac Grand Am
2.2L 4 Cyl (Ecotec)

Engine will turn over fine (Cranks & has spark) but fuel pump isn't running.

I checked the fuse. The fuel pump and injections run on the same fuse. Checked the fuse and Fuse is fine (checked with Digital Meter).

I checked the F/P relay. It works.

Fed power (12v) to the relay and the Fuel injectors clicked (working), but fuel pump will not turn on.

Jacked up car, crawled under it, found F/P harness, applied 12v power and I can hear the pump run.

So... the fuel pump DOES work, but for some reason it appears the cars PCM will not give power to the F/P relay to turn on... Why is this?

Suggestions?
 

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where did you apply power on the relay. The injectors shouldn't click cause I beleive they are ground controled by the pcm along with the fuel pump relay
 
If the PCM does not see a crank signal then it will not turn the pump on. Or if the crank signal is out of phase with the injector timing. I know you said you had spark but is it coming in at the right time ?
 
Could this problem be linked to the GM theft deterrent? I'm thinking the theft system is acting up, maybe the PCM isn't telling the F/P relay to energize. Can I shut the GM theft deterrent off W/O a GM Tech2? thoughts?
 
fzsk4p said:
If the PCM does not see a crank signal then it will not turn the pump on. Or if the crank signal is out of phase with the injector timing. I know you said you had spark but is it coming in at the right time ?
Click to expand...
the pump should stil cycle at key on
 
uluz2a6 said:
Could this problem be linked to the GM theft deterrent? I'm thinking the theft system is acting up, maybe the PCM isn't telling the F/P relay to energize. Can I shut the GM theft deterrent off W/O a GM Tech2? thoughts?
Click to expand...

theft deterant kills the injectors
 
Open up the fuse box and check the pins. Alot of times they will corrode and or burn out. Also on some models the pcm is a high side B+ signal instead of ground. I would doubt it is a pcm failure. I would check the switching pins for power/ground and if that checks out look for continuity to ground from the relay output power pin. 87a or pin 30 pins 85 and 86 are gonna be the relay switch control circut.
 
UPDATE:

Ok.. I HAD TO take it to a ASE master mechanic. He looked at it and said the underhood electrical center (fuse box) is only getting power to 1/2 the box. Also the fuel pump relay was too loose. He flipped the box over and made the relay housing connection tighter so the relay connects better. He suggested changing the box out with a used one from a junk yard. The other issue was the key cylinder might need to be replaced. A new key cylinder is around $130 and there is a special procedure to change it out (or so he said). So all in all, this was not a simple fix. The guy who fixed it was GREAT. He only charged me $40 for his diagnostic time.:banana:
 
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uluz2a6 said:
UPDATE:

Ok.. I HAD TO take it to a ASE master mechanic. He looked at it and said the underhood electrical center (fuse box) is only getting power to 1/2 the box. Also the fuel pump relay was too loose. He flipped the box over and made the relay housing connection tighter so the relay connects better. He suggested changing the box out with a used one from a junk yard. The other issue was the key cylinder might need to be replaced. A new key cylinder is around $130 and there is a special procedure to change it out (or so he said). So all in all, this was not a simple fix. The guy who fixed it was GREAT. He only charged me $40 for his diagnostic time.:banana:
Click to expand...

Fuse box problems are common thing in GM's. I have done a ton of repairs to them due to coroded wires. Really just a pain in the ass trying to track down the problem, if you ask me. I've also had ignition switches go bad and not send power to parts of the fuse block, but normally that will effect one entire row and not just one elemnt of the fuse block. Good thing you found an honest mechanic that explained to you these problems and didn't really charge you anything . . . but please don't get a junkyard box, because lord knows it will just happen to that one, try cleaning your factory coroded wires first before anything.
 
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