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#1
09-11-2006, 02:12 PM
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cranks but wont start
Heres the problem.....engine cranks with good speed but will not start. the fuel pump never cycles and i have swapped the relays and checked for bad fuels. i have replaced the fuelpump. i have checked the ignition it is firing the plugs it is. my question is is the fuelpump controlled by the ecm/pcm? I dont believe it is i suspect the oil pressure sending unit is my problem.
 all comments welcome....thanks97 gtp grandprix supercharge 3.8L 
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#2
09-11-2006, 02:30 PM
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Re: cranks but wont start
It would be helpful to post the year, model, engine size and mileage so members can weigh-in to help you.
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'08 Pontiac Grand Prix GXP (Dark Slate Metallic) - LS4 5.3L V8 '02 Oldsmobile Alero GL2 - LA1 3400 V6 '99 Buick Regal LS - L36 Series II 3800 V6 '03 Honda CR250R MX - 2 Stroke 250cc '97 Pontiac Grand Prix GTP - L67 Series II 3800 V6 Supercharged (Sold) Timeslip 08/12/06 AF Community Guidelines
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#3
09-11-2006, 03:50 PM
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Re: cranks but wont start
When you take ignition to on do you hear the fuel pump prime for at least 2 seconds?
In a GTP there is a 2 speed fuel pump due to having two control relays. Fuel pump and fuel pump speed control. The fuel pump is controlled by the PCM module via the 2 relays. The speed relay has a resistor that can go bad causing fuel system problems. To properly check the fuel pump, check fuel pressure at the front fuel injector rail on the Schrader valve of the fuel pressure regulator. On a GTP it must be in specs. The oil pressure sending unit should not cause your problem so I would rule it out for now.
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'08 Pontiac Grand Prix GXP (Dark Slate Metallic) - LS4 5.3L V8 '02 Oldsmobile Alero GL2 - LA1 3400 V6 '99 Buick Regal LS - L36 Series II 3800 V6 '03 Honda CR250R MX - 2 Stroke 250cc '97 Pontiac Grand Prix GTP - L67 Series II 3800 V6 Supercharged (Sold) Timeslip 08/12/06 AF Community Guidelines
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#5
09-11-2006, 06:03 PM
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Re: cranks but wont start
nope the relays were good no pressure at all at schradervalve. the fuel pump never cycles at all. i have changed the fuse for the fuelpump and ecm just to be safe.
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#6
09-11-2006, 06:36 PM
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Re: cranks but wont start
Quote:
12 volts will always be present on one side of the relay coils at ignition to on. The PCM supplies a low or ground to the other side of the relay coil.
__________________
'08 Pontiac Grand Prix GXP (Dark Slate Metallic) - LS4 5.3L V8 '02 Oldsmobile Alero GL2 - LA1 3400 V6 '99 Buick Regal LS - L36 Series II 3800 V6 '03 Honda CR250R MX - 2 Stroke 250cc '97 Pontiac Grand Prix GTP - L67 Series II 3800 V6 Supercharged (Sold) Timeslip 08/12/06 AF Community Guidelines
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#7
09-11-2006, 07:02 PM
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Re: cranks but wont start
with relays installed no power at fuelpump....ignition on and during attempt to start. 11.75 volts at f/pmp spd relay socket 1 and 2 connectors. 9.61 volts at fuel pump socket 1 and 2 connectors. trying to do a continuaity test now on the fuel pump harness..........any other ideas THANKS
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