Chevy 350 TBI help - Won't start... (1 Viewer)

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jesus888

jesus888

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Alright boys... need some help... who would you take your truck to (in Atlanta) or what else would you try if you had this problem
  • Chevy 350 TBI out of a 92 Chevy 1500 pickup (was a crate motor)
  • Driving last week, and it stalled and can't get it started... noticed coil wire disconnected from distributor, plugged back in, truck turns over, just won't start...
  • First checked to see if I was getting fuel, pump kicks on and fills the bowl...
  • Ran diagnostic on ECM and get one code (12) and that is just the startup code, so ECM not telling me anything is wrong
  • Decided since fuel wasn't an issue, it was likely the spark...
  • Replaced coil, replaced Ignition Control module, visually checked rotor, distributor isn't moving (it's tight), cap is tight, new coil wire installed... still nothing...
  • HELP PLEASE :)
 
jesus888 said:
Well, by bowl, I mean, fuel comes out of the 2 injectors that fire downwards into what looks like a bowl. It's fuel injected. TBI setup.
Click to expand...

The distributor module are notorious for going bad on TBI's. In most cases if any of the TBI electronics go bad it will code or go into default mod but will still start. A bad module will not show up with a code.
 
Check the wiring from the ignition switch to the ECM, maybe something else came loose and it's not getting a good IGN hot signal?
 
afraptor22 said:
Check the wiring from the ignition switch to the ECM, maybe something else came loose and it's not getting a good IGN hot signal?
Click to expand...

Totally disconnected computer, waited 5 min, and reinstalled... Good connections there. Also replaced fuel pump relay, and 2 fuses (neither were blown) coming off that harness (labeled battery and ignition)
 
Known good part!!!, I have seen new modules that were bad, try another tbi/tpi distributor and coil you know are good, one more thing tbi/tbi stuff eats coil wires, ohm the coil wire..

its a real simple system but the electronic pickup and the modules don't last forever. modules can even ohm good and fail to function.
 
FYI - Alldata DIY for GM pickups have very nice trouble shooting diagrams.

Did you check to see if you are getting power to the system (ignition and start)? Could be a blown fuse.
 
Did you make sure the ICM and distributor surfaces were CLEAN, and did you put dielectric grease on the surfaces?????
 
I have the same motor, same problem, just quit. It was the fuse for the injectors. A separate fuse I didn't know existed. You maybe already replaced it?
 
jesus888 said:
Alright boys... need some help... who would you take your truck to (in Atlanta) or what else would you try if you had this problem
  • Chevy 350 TBI out of a 92 Chevy 1500 pickup (was a crate motor)
  • Driving last week, and it stalled and can't get it started... noticed coil wire disconnected from distributor, plugged back in, truck turns over, just won't start...
  • First checked to see if I was getting fuel, pump kicks on and fills the bowl...
  • Ran diagnostic on ECM and get one code (12) and that is just the startup code, so ECM not telling me anything is wrong
  • Decided since fuel wasn't an issue, it was likely the spark...
  • Replaced coil, replaced Ignition Control module, visually checked rotor, distributor isn't moving (it's tight), cap is tight, new coil wire installed... still nothing...
  • HELP PLEASE :)
Click to expand...
With key on and a 12v test light is their power going to the coil from the switch. When you put the test light on the negative side (tach) do you get a pulsing lamp? On my Tbi no start, I had no pulsing...turned out the negative connection in the pigtail connecting the coil to ICM had melted do to a loose connection. Spliced in a new terminal and fired right up and got me from Utah to Anchorage. Then I bought a replacement pigtail...

Chris
 
Cdbailey said:
With key on and a 12v test light is their power going to the coil from the switch. When you put the test light on the negative side (tach) do you get a pulsing lamp? On my Tbi no start, I had no pulsing...turned out the negative connection in the pigtail connecting the coil to ICM had melted do to a loose connection. Spliced in a new terminal and fired right up and got me from Utah to Anchorage. Then I bought a replacement pigtail...

Chris
Click to expand...
To see the pulsing you need to have someone turn the motor over while you probe the tach terminal on the coil..
 
The ECU is live
The fuel pump primes when you turn the key on
The injectors pulse and inject fuel into the throttle body
The distributor must be sending a rpm signal back to the ECM to pulse the injectors

That only really leaves the coil circuit or some problem with the distributor if your not getting any spark
 
sadam_husain said:
The ECU is live
The fuel pump primes when you turn the key on
The injectors pulse and inject fuel into the throttle body
The distributor must be sending a rpm signal back to the ECM to pulse the injectors

That only really leaves the coil circuit or some problem with the distributor if your not getting any spark
Click to expand...

Only thing I didn't check/replace was the camshaft position sensor... which I read may be the issue... sending it to a local shop this AM... I'll keep the thread posted.

Thank everyone for the suggestions
 
I don't think those TBI motors had a cam or crank sensor I think all the referencing comes from the distributor signals

The shop will sort it out for you mate good luck getting it running again :)
 
Goooood question...

After changing everything in the ignition, and inspecting everything else, I was at a loss...

Towed to a local shop and turns out UNDER the rotor, once removed, there were obvious burn marks (I just inspected from the top)... so 1 x $7 rotor later, everything ran like a champ!
 
jesus888 said:
Goooood question...

After changing everything in the ignition, and inspecting everything else, I was at a loss...

Towed to a local shop and turns out UNDER the rotor, once removed, there were obvious burn marks (I just inspected from the top)... so 1 x $7 rotor later, everything ran like a champ!
Click to expand...
Woa. Well I will look at that carefully, got a no start issue myself right now. Thanks for the reply
 
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