Fuel Pump?

[bshadow998]

I have a 1999 Grand Prix GTP, it drove just fine an hour ago and then when I went out to go to the store it would not fire. It turns over just fine but cant even get a sputter out of it. When I sit in the car and engage the key to the "on" posistion I cant hear the pump engage, but then again, this is only a trick I have learned on other cars that I have had. It has 112,000 miles on it and the pump has never been replaced.

Is this a pretty clear sign that the pump is bad or shold I check some other things. I am also going to throw myself under the bus here and admitt that I am one of those people that runs his tank almost empty before filling up, now I learn that can heat up a pump pretty good and shorten the life. Lesson learned.

Thank you in advance for your help

 

[BillBoost37]

Check the resistor. Doesn't sound like the typical failure, but it's worthwhile to check it.

http://www.grandprixforums.net/fixing-your-intermittent-stalling-problem-26549.html

 

[bshadow998]

Thanks for the tip. Tried to bypass the resistor and no dice. Dont get any pressure at the rail either nor can I hear the pump engage.

 

[agentbluescreen]

The low pressure fuel pump fuse-resistor only works after the engine has started-up at full power fuel pressures. There are generally two relays that control the fuel pump circuit most years the one turns the pump on or off at full power (55psi) and the other "speed" one (once the engine is running) swaps-in the expensive GM fuse-resistor to drop the power to the fuel pump motor (44psi) thereafter, unless greater than normal fuel-use demands are sensed.

Try swapping the two relays to see if one has a bad Normally Open contact - this would cause the engine to start and then die, instead of not starting at all, if the fuel pump is still ok, and would mean that what is now the "fuel pump speed relay" (formerly the fuel pump relay) is no good. You may not necessarily be able to hear the fuel pump, try bleeding the fuel rail (covered tire pressure-type pin-valve) with a small screwdriver tip and rag to absorb the fuel, to see if it spurts pressure - if it does, fuel may not be the issue. If it doesn't spurt fuel it sounds like the fuel pump, it's motor wiring or it's main relay or it's fuse are gone.

A $2.00, 75 watt, 12vdc MR16 quartz-halogen track lighting bulb is the best replacement for a blown original low-speed fuel pump (fuse-)resistor, but this cannot be your problem, or the engine would (repeatedly, always) start and die.

Check to see if you have any spark while cranking.

If not, it is most likely magnetized stray brake-rotor filings stuck on the center magnet of the CPS (crankshaft position sensor) that weaken it's magnet preventing the two transistors in it from getting tach and timing signals. (it's under the main-bottom "harmonic balancer" pulley, next to the passenger wheel well).

This magnetic Hall-effect transistor "CPS" sensor "virtually" functions as both ignition "points" (and tach) and as a "distributor rotor" on these sorts of computer controlled ignition, MP-EFI engines and control the entire show.