fuel system help!
Thread Starter
Drifting
Joined: Jul 2003
Posts: 1,613
Likes: 0
From: Orlando FL
fuel system help!
Well, I finally got a fuel pressure gauge, hooked it up and everything seems to be in spec with the book. Holds about 36 psi after the pump primes (engine off) and runs around 30 psi at temp. There was a SLOW drop in pressure with the engine off (maybe a pound or two over 5-10 minutes). I was hoping to find a simple solution, either Fuel pressure regulator gone bad or EGR or IAC or even a dying pump. There are no codes and all of the charts and checks come back fine. But the car still has some stumble in it sometimes until it hits 150* or so (especially in the cold). Also, there seems to be a delay in acceleration when you jump on it, but then it frees up. I’ve seen it characterized as “running through molasses”. That’s about right….what am I missing? Could it be a vacuum leak somewhere, and if so, how do you test all the vac lines without equipment?
Safety Car
Joined: Dec 2004
Posts: 4,088
Likes: 0
From: Poop land
EGR has nothing to do with fuel pressure, but since vacuum hoses are connected to it, it might be a vacuum leak. The last time my fuel pump died, the pressure was 37 psi primed and about 30 psi at temp like yours. Had really bad problems with hesitation at one point. Then I bought a new pump from Autozone for like $75, put it in and now the car makes the 43 psi of fuel pressure my Vette needs. Dunno how different an 85 is to an 89 but anyways good luck.
Le Mans Master
Joined: Dec 2004
Posts: 5,789
Likes: 8
From: Myrtle Beach SC
St. Jude Donor '05-'06
Can't test without the tools.I bought a Mityvac off ebay for $30.It will do testing and bleed the brakes too.Well worth the money it has paid for it self with just the brake bleed.An EGR will weaken over time and start to leak vacuum as I am having some issues in that area right now I can say my old one would not hold a vacumm for any time at all.They will leak down with a vacuum on it but it should take around 20sec for it to happen.
Safety Car
Joined: Dec 2004
Posts: 4,088
Likes: 0
From: Poop land
Isn't fuel pressure also controlled by vacuum as well? I remember seeing a vacuum line connected to the fuel pressure regulator. You might wanna check the vacuum line leading to the FPR because that means you could be getting too much or too little fuel if that line is cracked or split.
Thread Starter
Drifting
Joined: Jul 2003
Posts: 1,613
Likes: 0
From: Orlando FL
sometimes the idle hunts between 660 and 750...slowly...until it gets nice and hot and going...is there a way to spot leaks with a light mix of water ond soap or something? (i thought i saw that here once)
