99 gtp starts then dies..

[2004pontiac]

Hello, we had a 99 gtp towed in today, just died. Any way it will start and die, start and die unles we give it throtle. First we noticed the SC belt and idler pully was gone. But customer said its been running like that. So we did a fuel psi text. with key on gauge shows 55psi, Then when it fires up drops to approx 45 then the gauge drops stedly to zero and dies at approx 15psi. Humm so we did the cheap changed filter, no good same reading, checked psi reg seemed ok but we changed it, same readings.. so humm fuel pump thats all thats left right.. so we had a good one. Changed it over and still same syptoms, 55 with key on then 45 under crank, then when it start the psi stedly drops to zero.. car dies. not if i chasing my tail,barking up wrong tree or what.. any ideas?

Thanks

BTW the iac,tp,map and mas have been changed.. with no change.. its like the fuel pump stops.. we also changed the relay..

 

[BlackGT97]

change the fuel pump. only other option at this point.

 

[rocknnachos]

The outgoing power from fuel pump relay doesn't go straight to the fuel pump. It goes out through a fuel pump resistor and then back up to the f/pmp spd cont relay. I think its right beside the f/p relay. So the f/p relay would be hot at the #30 terminal goin out and the f/p spd cont relay would be hot at #87A goin in. Could be the resistor.

 

[BillBoost37]

You'd want to test power going to the pump before changing a pump. Nacho his it on the head when he asks about the fuel pump speed resistor. When the key is turned the car primes. Then that pressure in the line will bleed off like you mention unless the pump kicks back on. This is very common.

 

[2004pontiac]

update, sty been a while,, anyway we found a fuel pump speed resistor.. (.08 0hm ballast) called the dealer and they didnt know bout it.. they found it and it cost 60 bucks wow....