I have had an ongoing problem with my 91 TA. It has a 305 TPI, it would drive alright, but as soon as i floored it and it got ready to shift the engine would just cut out, and it was knocking like hell and it would sputter around and finally die. Sometimes it would not even start and run after this would happen. If you kert after it, all of a sudden it would start up fine and run like hell until you florred it again. I have had it to the dealership twice. Tyhey checked the EGR and all of the injectors are still fine. They are clueless. Now, the car is sittin gin my garage dead. I can not even get it to start. All of the fuse are ok, new plugs, wires, cap, rotor, and fuel filter. All of the wires are firing. The car has never given an error code. A friend of my dad said that it could be a bad fuel pump. It will crank, but not fire. He said that the pump must push out a certain pressure to open th injectors. So if i have a bad fuel pump how do i find out???? Is there any way i can do a test?? Any ideas would be appreciated because i miss my car.

Thanks

 

He is thinking of CPI and SCPI, this does not apply to your car because you do not have poppet nozzles.

If you suspect you have fuel pump problems, you NEED to hook up a fuel pressure gauge. Simply depressing the schrader valve and seeing how far fuel squirts will not help you. (unless none comes out at all).


------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
JET AFPR,
Ported Plenum,
TB Coolant Bypass,
SSM SFC,
Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
KYB Shocks
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

 

It's also a good idea to know what the fuel pressure is doing at WOT (wide open throttle) - it should be no lower than 46 psig, or so with the stock regulator. If you have an adjustible fuel pressure regulator, run it at around 50 psig, or so. You'll need a gauge with a hose long enough to reach to the windshield - so you can look at it while you're driving, or a dash mounted (permanent) gauge, or run the car on a chassis dyno with an under hood gauge. Also, there's a fuel pump test connector near the fuel pump relay on the driver's side fire wall - it's a red wire with a connector on the end - you may power the fuel pump directly from the + terminal of the battery to test it out, without running the engine.

Hey, GMTECH, what are CPI & SCPI? Just curious....Thanks.

Tim

 

CPI is Central Port Injection. It was used on the 6 cylinder, 4.3L "W" from about '92 to '95. It had one fuel injector wich feed six poppet nozzles. The Poppets had a little ball valve at the end, and when the injector opened, it put pressure behind the poppet nozzle, and the fuel pushed the ball valve off its seat, and the fuel sprayed.

In '96, GM went to SCPI, wich is Sequential Central Port Injection. It is basiclly the same, but instead of one injector, there are six. So each poppet nozzle has its own injector, so the system funtions the same, but now is sequentially fired. The poppets must see a minimum of 55psi before it will unseat, so if the fuel pump is weak, the truck simply won't start. But none of this pertains to Fbodies.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
JET AFPR,
Ported Plenum,
TB Coolant Bypass,
SSM SFC,
Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
KYB Shocks
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

 

Thanks for the info....

Tim

 

Hey there,

I'm new to this forum but not TA Problems. Here's something I hope will help. Before you try to start it verify the fuel pump is even tuning on. Have a friend turn the key on and off while you stand in back ear to the open gas cap and listen for a short 2 sec whining noise. If you hear it at least you know the pump is turning on with the key. If you don't hear it then pump may be no good. Now, to get it to start try removing the vacuum hose from the fuel pressure regulator. It's located on the passenger side at the back of the intake plenum connected onto the side (right behind the plenum's chrome or aluminum pipes) connected to the regulator (which is under the plenum at the rear of the intake manifold)
Next, crank the car over while a friend watches for fuel squirting out of the disconnected vacuum line. (BE SURE TO POINT IT AWAY FROM ANY SPARKS AND BE CAREFUL!)
If all else is well the car SHOULD start. If there is fuel squirting from the pressure regulator vacuum hose WITH OR WITHOUT THE CAR RUNNING then the regulator needs to be replaced.
If no fuel squirt then ONCE THE CAR STARTS reconnect the vac hose and listen for a weird idle change. Once you hear the change quickly disconnect the vac hose again and you should see fuel running out from the regulator. BAD SIGN
another quick check for a broken fuel pressure regulator (IF YOU DON'T WANT TO RISK GAS EVERYWHERE) IS TO START THE CAR, feel all the intake plenum's pipes. They should all be the same temp if all plugs are firing properly. If one set feels "Ice cold" compared to other sets of 2's then there is most definitely liquid gas in stead of vapor getting into the cylinders getting the plugs wet causing one or more "dead cylinders" Hope this helps. Let me know

Greg "Sho Nuff" Tatum