Cranks but will not start is it the fuel pump relay

MATT MACKIEWICZ

MEMBER
2004 PONTIAC GRAND AM
3.4L
6 CYL
FWD
AUTOMATIC
140,000 MILES

Turning over not starting. Swapped the fuel pump relay with another relay fired right up couple hours later turns over, but not starting. Tried swapping relays again, no luck this time.

Saturday, January 21st, 2017 AT 7:11 PM

3 Replies

STEVE W.

MECHANIC
13,591 POSTS

If swapping the relay helped it is very likely a bad fuel pump. Do you hear the pump turn on when you first turn the key on? It will prime for two seconds. If not a quick check is to reach under the car and give the fuel tank a hard whack. Many times that will jar the pump enough that it will start working again. Still a bad pump but now you know it is a bad pump.
The tank has to come out to replace that one.

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Sunday, January 22nd, 2017 AT 1:58 AM

MATT MACKIEWICZ

MEMBER
1 POST

Fuel pressure gauge on fuel rail 52 at prime 60 at attempted start. NOW check this out hooked up a snap on computer forced the injectors to pulse which they did (when told) and the car started right up. SO the injectors are now being told to pulse when starting

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Wednesday, January 25th, 2017 AT 7:15 PM

STEVE W.

MECHANIC
13,591 POSTS

OK, no injector pulse is usually a bad crank or cam sensor GM uses input from both. You should be able to use that SO tool to see all 3 and tell which is sending the bad signal.
The 3.4 has 2 crank sensors and one cam. The cam sensor is mounted where the distributor used to be. The cranks sensors are split. One is up front by the crank pulley the other is mid block and reads the crank ring. They are Crank A and Crank B on most scan tools.

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Wednesday, January 25th, 2017 AT 9:20 PM