1993 Suburban Issues

[Chris 69]

For my dad, who is 4-hours from where I live.....

He has a 1993 GMC Suburban 2500, 350, auto, throttle body.

My uncle borrowed the Suburban. When he was using it it died suddenly. He restarted it and it ran fine. My dad picked it up later that day, got to the bottom of the hill and the car died. It would crank, but not start. The car had to be towed home.

Last weekend, he replaced the fuel pump (located in the gas tank). It still turns over fine, but will not start. If gas is poured down the throttle body, the car will start and run fine indefinitely (above 1200rpm) off the fuel in the tank. Once shut off, it will crank, but won't start.

Sometimes, if he keeps cranking the engine for an extended period of time, the car will eventually start.

When the engine is running, it will run fine above 1200rpm, but below 1200rpm, the engine will die.

My guess (and I am not the greatest mechanic) is that there is a fuel pressure regulator in the system that has failed and is allowing too much pressure.

Questions:

1. Is there a fuel pressure regulator in the system?
2. Any advice as to what the problem could be?

Any help is greatly appreciated.

Thanks, Chris

[bull]

Kind of sounds electrical to me. Do those things have a pickup plate in the distributor in lieu of points?

[captnsim]

First thing to do is figure out for sure if its fuel or spark that's causing your issue.
Regulator is in the throttle body. To figure out if it's bad do a fuel pressure test. These are known to get "sticky" with age.
You could also be loosing pulse width to the inj's. A noid light is used to determine if you have pulse. Also early tbi gm's are  known for computer failure due to bad internal connections. A light tap on the computer if bad will cause a miss or stall. Also inspect the fuel pump relay.
The pickup in the distributor is also known to deteriorate and cause a intermittent no start. Unfortunately to test this requires special tools.
Bull...Yes these have a reluctor plate in-place of points.
   

[Chris 69]

Kind of sounds electrical to me. Do those things have a pickup plate in the distributor in lieu of points?

Bull, it is electronic as captnsim states.

captnsim, thank you for the information, I will forward it to my Dad.

Chris

[bull]

Kind of sounds electrical to me. Do those things have a pickup plate in the distributor in lieu of points?

Bull, it is electronic as captnsim states.

captnsim, thank you for the information, I will forward it to my Dad.

Chris

I know it's electronic, I'm just asking if it has a pickup plate. Those are notorious for going intermittent.

[Chris 69]

Kind of sounds electrical to me. Do those things have a pickup plate in the distributor in lieu of points?

Bull, it is electronic as captnsim states.

captnsim, thank you for the information, I will forward it to my Dad.

Chris

I know it's electronic, I'm just asking if it has a pickup plate. Those are notorious for going intermittent.

Thanks Bull, I'll check to see if it has a pickup plate.

[no318]

Magnetic pickup distrubtor.  The magnet can break, crack, fail and cause low output.  ATLEAST 400mv AC volts with a DVOM coming out of the pickup coil in to the module (under the dist. cap).  Obviously the faster it spins, the higher the AC voltage amplitude out of the pickup coil.  IF this is the problem on yours, sometimes, they will start better with a jumper box/start because the higher cranking RPM is just enough higher that the pickup coil signal is just high enough for the ignition module to recognize that it is running.  Module relays RPM info. to ECM.  ECM triggers injectors.  You will have no spark (module) and no injector trigger (ECM) if there is no RPM input.

[Chris 69]

Magnetic pickup distrubtor.  The magnet can break, crack, fail and cause low output.  ATLEAST 400mv AC volts with a DVOM coming out of the pickup coil in to the module (under the dist. cap).  Obviously the faster it spins, the higher the AC voltage amplitude out of the pickup coil.  IF this is the problem on yours, sometimes, they will start better with a jumper box/start because the higher cranking RPM is just enough higher that the pickup coil signal is just high enough for the ignition module to recognize that it is running.  Module relays RPM info. to ECM.  ECM triggers injectors.  You will have no spark (module) and no injector trigger (ECM) if there is no RPM input.

Thank you. This will be checked as well