My injectors arn't working and the car is not firing. The fuel pump is not working etheir, the fuse and relay is good. I've been trying to fix the pump for a few weeks now. While I was waiting on some parts I changed the valve seals, and today got the valve covers back on and went to fire it up and it was a no go! The tach ran real high( it would turn up 7gnd like nothing) before and the Chevy dealer here told me it was controled by the ECM and that is what I would need to get to fix the tach. So do ya think it is the ECM and now it has went out for real? Thanks, Bobby

 

Tach is controlled by the ignition pulses from the coil. If the tach goes high while cranking then it is possible that the igniton system has a problem. Coil, pickup coil and ignition module are good suspects.

I would at least get the fuel pump operational before tackling the tach (could be a bad tach too). At key on (do not crank) the fuel pump should run for two seconds and stop. This is ECM controlled via the fuel pump relay.

RBob.

 

Double check for having mashed a wire under a valve cover. EZ mistake.

 

Well its not the ECM. And no mashed wires. As for the fuel pump I'm running a Holley Blue Pump now. The pump went out about 2 years ago, and the car has just set up. Dont know about all years, but '91-'92 has 2 plugs with 2 wires(4wires in all) in each plug coming out of the coil. All 4 of these show hot with a test light, with the ignition on, but no fire comes out of the coil wire to distribor(bad coil?). I'v got a Matco Tools #NLT8837A TBI/EFI Injector Tester Kit(it is a set of 5 lights(you use only one light per car, it works on several different cars) that plug into the 2 wire harness that plugs into your injector. The light should flash when turning the car over to confirm voltage pluses are going to the injectors, well I get no light. I tested it on my buddeys car and it is working. Is it possible that the coil is bad and when the ECM realises the distribor is getting no fire that it kills power to the injectors(my Nissian's cam broke and the distribor didn't work so the ECM in it killed my fuel pump, I bought 2 new ECM for it before I found that out)? Someone please give me any ideas! I'm swaping to a carb soon but for all the stuff that I still need it would cost $1200 and I just can't do that right now! In desperate need of help, Bobby

 

All four wires showing hot with the ignition on is likely correct. The large pink is B+ from the ignition switch, the white wire in the same connector is the tach feed (goes to the tach).

The other connector (on the coil) is B+ to the ignition module and the coil trigger from the ignition module. Also, in order for the ECM to fire the injectors it needs to get reference pulses from the distributor.

In this case I'd say we are back to either the pickup coil, ignition module or the coil being bad. If you can swap out the distributor and coil for known good ones that would be a good test.

RBob.

 

Well I tried my coil on a '91 4.3L S10, they looked the same & the wire connectors were the same, and the truck would not start. I'm almost postive the coils are interchangeable. I know that MSD sells only 2 GM Blaster coils(one wire & two wire connectors). Does anyone know forsure if these coils are the same? Please help, Bobby

 

Well I tried my coil on a '91 4.3L S10, they looked the same & the wire connectors were the same, and the truck would not start. I'm almost postive the coils are interchangeable. I know that MSD sells only 2 GM Blaster coils(one wire & two wire connectors). Does anyone know forsure if these coils are the same? Please help, Bobby