hi, i have a 99 pontiac grand prix GTP. last monday when my wife pulled in to the grocery store and shut it off, and then came out and started the engine it would only run for 4-5 secs then die. SHe was low on gas so i figured it was too low. So me and dad went to the rescue and put some gas in and same thing. it will start great and then smother right out. BUt if you pour gas in the intake it will run fine. So we loaded it on the trailer and took it to the garage. The check engine light is not on, but i put it on the computer anyway and no trouble codes showed up. WE tried a fuel pump and no better, then a fuel filter and nothing, i have also tried a throttle position sensor, Module that the coil packs bolt to.Fuel pump relays. So here is finally i guess what i need to know. WHen i turn the key on the pump kicks on for maybe a couple secs and pressures up and then when i start the car the pump doesn't offer to run and i guess what little the car does run it is just using up the pressured gas. What would tell the fuel pump to run while the engine is running. when the engine starts to die the fuel log has zero pressure. I'm about out of guesses. Thankfully dad is letting me try the parts. I hate to give up and take to any local garages, they aren't none to brag about and would probably rape me switching parts which is what i'm doing. if anyone on here has had any run ins with a problem like this and can help me i would appreciate it. thanks Bo
When did the HAMB become a tech line for all that is automotive? Should be plenty of sites/forums besides here that could help ya.
when you turn the key on you should hear the pump run for about 2-3 seconds then it shuts off when the engine starts its supposed to switch the pump back on, sounds like its not switching the pump back on. I believe there is a relay and module that controls the pump on those assuming you have already checked for the filter being plugged up I would look at that first or you could have a bad pump too
the fuel pump comes on with key on to prime system then cuts off until the ECM recieves an engine speed signal, then the ECM signals for the fuel pump to run, you will need a diag manual to see where the engine speed signal is coming from. some cars use the alternator output as the signal that the engine is runing and others use crank sensors Larry
Your right, the pump kicks on for 2-3 secs then off and when i hit the key and start the engine the pump never comes back on till the engine totally shuts off and then it repressurizes. I changed the pump and filter. the relays in the underhood fuse compartment. I have racked my mind trying to figure what to try and where it may be. The fuses under the dash all looked good also. I figured i would give a shot here because i spend alot of time looking and reading here on with so many members i thought maybe someone may have a similar experience. I appreciate any help or ideals that i can get.
I had a service van that did this and it ended up being the ignition switch drove me nuts. it had a security sensor go out so it killed the pump when youd start it . It thought it was being stolen.
hey larry, that info makes alot of sence. i will try to find out what the ecm uses for the speed signal. I will try to get a manual or keep searching the net and see if i can find what the ecm relies on. thanks alot Bo
Ran into an issue like this a while back on the wife's Buick... turned out to be the crank position sensor.... drove us batty. Normally, when they go, they just flat go.... hers, for whatever reason, would send just enough signal to get everything going, then send a batty signal.
Are you sure you've found the fuel pump relay? If so I guess at Crank Sensor to, and key code/Key/ignition switch as a second guess, come to think of it reverse those answers.
thanks for all the helpful information that you all have gave me today. Now i have some confidence that tomarrow will be a better day trying to figure this car out. I realize that this is a traditional board but i know it is also about helping fellow hambers out also. Your interest and help are greatly appreciated and maybe it will save me some major bucks so i can get the hemi roadster on the road. thanks Bo
Sounds like a security system problem to me -- I am a tech at a GM dealer I should add -- you wont get a check engine light if it is a security issue but it should set a code in the passlock system -- depending on what type of scanner you are using you may or may not get the code -- watch your security light when it stalls and see if it is flashing. Could probability you are gonna be needing a passlock sensor. This is a fairly common problem. Hope this helps.
My daily driver is my 1953 Chevrolet Bel Air.. you new car ninny! Sell that heaping pile of plastic and cup holders!
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