I have a 1989 S-10 Blazer with a 4.3 220 TBI engine.
It was spitting sputtering and dying out when accelerated. I replaced plugs, wires, cap & rotor. It ran pretty good until you nailed the accelerator, it would stumble until you let off some. Drove it for 20 min, parked it, came back out to drive it and it ran for about 10 minutes, then just died out all of a sudden at 35 mph, no miss or stumble just flat dead. Now I have no spark from coil to distributor and no throttle body gas spray from either injector. I have checked the TPS, it varies voltage properly. I changed the coil & ignition module, map sensor, replaced the fuel pump assemble and filter. I have also pulled the coded and got a 33 & 34, which is why I changed out the map sensor. I even pulled the ECM, looked it over for any obvious cold solder joints or water penetration or ached / burnt out components, everything LOOKED good.
The fuel pump runs for about 2 seconds when ignition is on, fuel is getting to the TBI but not spraying and no spark ANYWHERE. Engine turns over but sounds like its missing fire and gas
Help requested!

 

The pickup in the distributor is what sends the signal for both fuel and spark on a TBI. If you don't mind resetting timing you can take the distributor loose and turn it in either direction when the engine is not running but the key is in the run position. You should hear the fuel pump run for the 2 seconds as the pickup is triggered. That will tell you that the ECM is getting a signal from the distributor. If that does not happen you would either have a problem with the ECM, wiring or else the pickup in the distributor.

 

Thanks TZFBIRD,
It does run for a few seconds

 

So you are getting the reference pulse from the distributor but nothing as far as spark and fuel? If you get the fuel pump prime then the ECM has to know what is going on. I doubt both circuits would go bad at the same time but not for the fuel pump.
Have you checked fuses? There should be +12v on one side of the fuel injector connector. The ECM grounds the circuit in order to fire the injector. I believe it is the same for the ignition coil but I have not had to do much troubleshooting on my TBI ignition system so I am not 100% on that.

 

I do have the 12vdc at the coil.
Can I simulate the ground from the ecm? How?
Thanks for ALL your input. Stick with me if you will.
I can only work on it on weekends but am willing to try anything.

 

Unplug the vacuum line from the distributor vacuum advance and try it. When the advance pulls the breaker plate in the distributor, it pulls on the tiny wires to the pick up coil. The constant flexing causes the wires to break. VERY common to have intermittent problems as the strands of wire break. Once the last one breaks, no spark, and no injector pulse.

 

Thanks for that Captain Hook. I will try this tomorrow!

 

They still had vacuum advance in 89?

 

1989 "Z" (TBI) engine has an HEI distributor. Some had vacuum advance, some did not, but they both have a pick up coil with the tiny wires that can develop "issues". As you mentioned in post #2, the pick up coil is what generates the pulse for the ignition and injectors, so that's the first place to look for a problem in this case.

 

I learned something new today then. I figured if GM started 2 years prior having distributors without vacuum advance that it would have been phased out.