JMAC71

Hey Guys,
Hopefully you can help me. I have a 1997 Firebird. 3.8 Liter engine. Car has to turn over 4 or 5 seconds before it will start after sitting like an hour. I checked fuel pressure with guage. When you turn the ignition on, the fuel pump energizes for about 2 seconds and fuel pressure reads around 47 PSI. As soon as the pump cuts off (2 seconds) the pressure will not hold. In about 30 seconds it drops to almost zero. Therefore making the car hard to start due to lack of fuel pressure. What would cause the pressure not to hold? Pump, regulator, or injectors, etc? Once the car starts it runs fine. The pressure stays around 41 to 42 PSI with the car running. If you unhook the regulator with the car running the pressue goes up to 50 PSI. Hook the regulator back up and the pressure drops back to 41 to 42 PSI. Any help would greatly be appreciated.

thanks,
JMAC

eseibel67

iTrader: (10)

Your regulator is o.k.

Most likely culprits are the injector "o" rings.

The cost of the rings is minimal. Lift the fuel rail and change them all.

JMAC71

Thanks for the reply. I was leaning more towards something like a check valve in the fuel pump since the fuel pressure drops so quickly. Seems if the o-ring were bad it would let fuel go into the intake and cause a rich condition or flooded condition which would produce black smoke. I was curious as to what keeps the fuel from flowing back to the tank once the pump turns off till you crank the car? There has to be someway for it to hold pressure until you turn the motor off. I do see what you are saying that it is leaking into the cylinders as well but seems like it wouldn't drop that fast. I will give the orings a try if I don't find anything like a check valve.

thanks

camcamaro1991

iTrader: (18)

its the check valve in the fuel pump.
pump pressure should not drop/bleed off to zero.
although the running pressure was at 58 psi at idle
just did one in my GF's camaro, she had hard starts as well the pump would prime and then the pressure would fall to "0" psi within 3-4 seconds.
time for a new fuel pump.
i installed a racetronix pump.

added info

With KOEO the fuel pressure should immediately go to 43.5psi +/- 2 PSI

The next important thing to do is watch the gauge. The pressure should hold right about there. Any bleed off could cause no start, hard start or bad performance.

If the pressure drops slowly you could have a leak in a line or fitting or possibly a faulty fuel pressure regulator. Usually if you pull off the vacuum line to the regulator it will be wet if it is faulty.

Another cause of slow bleed down is a stuck or shorted injector. this will usually cause a hard start and can be very damaging to the motor since fuel is filling that cylinder when ever there is pressure in the lines.

If the pressure bleeds down fast it is usually due to a faulty fuel pump check valve and the fuel pump will need to be replaced.

JMAC71

Thanks for the info. Sort of what I was leaning towards. It doesn't leak down to zero in two or three seconds but it does do it in about 30 seconds. You can see the needle on the pressure guage going down as soon as the fuel pump shuts off. So out of curiousty, how hard was the pump to change? I know you have to drop the tank so it can't be all good. I was told there was another procedure where you can go through the trunk by cutting a hole and do it that way. Not too sure about that. Thanks again guys for the info.

JMAC

camcamaro1991

iTrader: (18)

heres a general thread and link for 99+


f-body dual pump thread, but the hole location applys

https://ls1tech.com/forums/fueling-i...ick-cheap.html

plastic tank 99+ web link.

http://www.gonicd.com/intankinstall/...mpinstall.html

i installed fuel pumps in my old 1991 camaro twice, by lowering the tank out the bottom, makes you never want to do it again.
i cut a hole in my GF's 02 Camaro and mine 02 Camaro as well. greatly reduces the time for pump R&R

JMAC71

A big thanks to you. This I can do. I have dropped the tank on one of these once myself and it was a PITA to say the least. I will for sure try this route. As long as the 1997 location is the same shouldn't be a problem at all. Since my pump seems to pump fine I was actually thinking of just going underneath and putting in a check valve right after the fuel filter in the fuel line to see if that would work. I found a guy in Alabama who offers the check valves just for this application. However with this procedure you have showed me, I think I will go ahead and just replace the pump. Again, thanks a lot and I will let you know how it turns out.

thanks,
JMAC

blkcamaro_z28

iTrader: (3)

Had my car do this last year, it ended up being the pick up line that runs to the the bottom of the tank had a small crack in it and all it is, is a small plastic hose that sucks up the gas to the actual pump at the top of the gas tank. The crappy thing is that you can't just buy a new little hose and slap it on there, oh no that would be way to easy lol, ended up buying a AC Delco fuel pump for close to 450$. But good luck, figured I'd give my 2 cents worth.

JMAC71

Thanks for all the help guys. Just out of curousity I went ahead and put a check valve in the fuel line since the pump would pump up correct pressure but wouldn't hold it. This fixed my problem, or it seems to have. Through some searching I found that there is a place in Alabama that came up with this check valve for the GM products due to this very problem. There is a check valve, or maybe the pick up that Z28 is referring to, that goes bad even though the pump still operates it won't hold pressure in the system and causes hard starting. I have the name and contact info for this valve if anybody has the same problem. Be sure to check your pressure first and make sure your pump is pumping to the correct pressure. If it is but just won't hold the pressure there, the chances are the check valve has gone bad. It is far easier than replacing the pump if there is no need to. However, I do like the going through the trunk to replace the pump and that is something I will try when I do need to replace my fuel pump.

again thanks for all the help,

JMAC

dlpow

Can I get the name and phone number please?

triblk6spd

iTrader: (2)

Old thread I knkw...If I install a full Racetronix fuel pump set up....does this set up have a new check valve and whatnot with it or woukd I need to get a new GM fuel pump assembly and add the Racetronix piece to it.
Mine has been slightly hard to start lately and Iv tracked it down to the darn check valve. Car runs mint other than that nagging issue.
Thanks all!

triblk6spd

iTrader: (2)

Nobody? ******* Racetronix?! Email AND phone messages STILL not replied. **** passes me off. If I ran my business like them I wouldn't me in business.