305 tpi, possible low fuel pressure or wrong mixture?
07-04-2011, 05:27 PM
#1
Junior Member
Thread Starter
Join Date: Nov 2010
Location: Mid-MO, Missouri
Posts: 55
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1989 Pontiac Trans Am
Engine: 5.0 TPI LB9
Transmission: 700r4
Axle/Gears: 10-bolt 2.73
305 tpi, possible low fuel pressure or wrong mixture?
Alright, so I have a 1989 trans am, 305 stock no mods
The fuel pump went out on me, so it has been replaced, car was running fine before, but now when I press on the gas it bogs, )it after a few seconds of holding the gas it straightens out and works just fine! Everything has been tuned up, new fuel filter, MAF.
I tested fuel.pressure at the rail and it will only read 20. FPR doesn't seem to be be bad, ( vacuum line pulled from top and checked) also getting a backfire in the intake? honestly at a loss as to what this could be! Help is appreciated!
The fuel pump went out on me, so it has been replaced, car was running fine before, but now when I press on the gas it bogs, )it after a few seconds of holding the gas it straightens out and works just fine! Everything has been tuned up, new fuel filter, MAF.
I tested fuel.pressure at the rail and it will only read 20. FPR doesn't seem to be be bad, ( vacuum line pulled from top and checked) also getting a backfire in the intake? honestly at a loss as to what this could be! Help is appreciated!
07-04-2011, 06:32 PM
#2
Junior Member
Join Date: Apr 2011
Location: Castleton, NY
Posts: 31
Likes: 0
Received 0 Likes
on
0 Posts
Car: '91 Z28, '04 2500HD
Engine: 5.7
Transmission: 700R4
Axle/Gears: 2.73
Re: 305 tpi, possible low fuel pressure or wrong mixture?
Your fuel pressure should be around 43 psi. The bog is because the engine is starved for fuel and running way lean. Has the fuel filter been replaced recently?
07-04-2011, 11:53 PM
#4
Junior Member
Thread Starter
Join Date: Nov 2010
Location: Mid-MO, Missouri
Posts: 55
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1989 Pontiac Trans Am
Engine: 5.0 TPI LB9
Transmission: 700r4
Axle/Gears: 10-bolt 2.73
Re: 305 tpi, possible low fuel pressure or wrong mixture?
Yes the fuel filter wasn't too long ago, but I'm probably going to pull it and see how dirty it is, and I brought the pump back and exchanged it twice for different ones. Tomorrow I'm going to replace the fuel pump pulsator with some hose, and see what that does. What should the fuel pressure be at an idle? I haven't put it under a load other than reving the engine, because my car doesn't go anywhere! Haha, thanks for the replays, and happy 4th guys!
07-05-2011, 08:11 PM
#5
Junior Member
Join Date: Apr 2011
Location: Castleton, NY
Posts: 31
Likes: 0
Received 0 Likes
on
0 Posts
Car: '91 Z28, '04 2500HD
Engine: 5.7
Transmission: 700R4
Axle/Gears: 2.73
Re: 305 tpi, possible low fuel pressure or wrong mixture?
The pressure at idle should be around 43 with the vacuum line unhooked. I would check all the electrical connections to the pump too.
07-07-2011, 09:26 PM
#6
Junior Member
Thread Starter
Join Date: Nov 2010
Location: Mid-MO, Missouri
Posts: 55
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1989 Pontiac Trans Am
Engine: 5.0 TPI LB9
Transmission: 700r4
Axle/Gears: 10-bolt 2.73
Re: 305 tpi, possible low fuel pressure or wrong mixture?
Replaced the electric connections at the pump, sadly don't have my fuel pressure tester now, but I'm thinking I have a bad injectori just don't know how to test them!
04-11-2015, 06:38 PM
#7
Junior Member
Join Date: Apr 2015
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
Re: 305 tpi, possible low fuel pressure or wrong mixture?
Hey did you ever solve your problem? I'm having the same issue and I'm starting to go in circles! New fuel pump and sending unit, new fuel filter, and new tps!!
Thread
Thread Starter
Forum
Replies
Last Post
R3500
Engine/Drivetrain/Suspension Wanted
1
08-17-2015 12:16 PM
