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cold start issue

W

War97gtp

New member
97 gtp 70k miles. On cold starts or if the car sits longer then 30 minutes after being driven it cranks for at least 5 full seconds before it starts, it used to fire up with the tap of the key. I tested the fuel pressure with the key on engine off, the pressure goes up to about 50 while the pump is priming, then when the pump shuts off it takes about 30 seconds for the pressure to go to 0. With it running pressure is at about 45 psi at idle and raises slightly when i blip the throttle. I dont think its the fuel pressure regulator because there was no signs of gas in the vacuum line when i pulled it off, and when its running and i disconnect the vacuum line to the fpr the pressure jumps from 45 to 55 so it seems like it is working properly.
Is there a check valve somewhere in the fuel system that is supposed to hold pressure when the pump is off, on the fuel pump maybe? could that be the issue?
 


Try pulling the line off the FPR again and letting it idle for a bit. Sometimes it takes a couple minutes before it starts to leak fuel through the diaphram.
 
Fuel pump check valve should hold pressure. Try this. Turn key to on, wait one second or two, then crank. Should start right up since you will have repressurized the fuel system prior to cranking. Gets you around the issue til you fix it. Troubleshoot why loosing pressure so fast. Bad check valve in fuel pump, fuel leak in lines, leaking injector, fpr leaking, etc. May need to trace fuel lines for a leak, pull fuel rail to check for leaking injector, etc.
 
No signs of fuel leaking anywhere and no signs of fuel in the fpr vacuum line. I actually have 2 97 gtps and just to compare i tested the pressure on the other one and sure enough it holds after the pump primes.
I also have a 02 camaro ss which had the same exact problem, replaced the fuel pump and it was fixed.
Im pretty confident its the fuel pump, its not so hard to replace on these cars due to the access panel in the trunk right? On my camaro i had to drop the exhuast, rear end and tank to change the pump.
 
On my 04 I can change the pump in 20 minutes. Pull the back seat down. Sit on it. Flip the trunk carpet up, unbolt the cover. Remove the lock ring, connections, and lines. Wiggle out. Thank GM for putting in an access cover!
 
I changed the fuel pump, but im not sure if the issue is fixed. The pressure actually drops even faster after priming takes only about 5 seconds to get to 0, however the car starts a little better only about 2-3 seconds of cranking. I read somewhere that some aftermarket pumps do not have check valves in them. Since i installed a delphi pump and not an ac delco is this possible? or did i get a defective fuel pump. Is there anything else in this fuel system that is responsible for holding pressure after priming.
 
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If it takes only 5 seconds to drop to zero pressure then their is a leak, the check valve in the pump (which the replacement has) is bad, a fuel Injector is leaking, or the fpr is leaking. Isolate and troubleshoot each component.
 
Here is an example of how to check for air loss. Run an air hose to the injectors or fuel pump, clamp it, and hook up 60 psi or so. Check it overnight and see how much loss you have.



 
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Well, as strange as it may sound I have not done anything and the problem fixed itself. Fuel pressure holds and the car starts perfect everytime hot or cold. It has been like this for about a week now. Can anyone explain this?
 


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