I bought a 1995 Chevy 2500 4x4 with a 7.4. The truck did not run, no fuel and no battery. The truck was side post and i do not prefer top post. I changed the battery connectors over to top post and purchased a 1000 cranking (800 cold) amps battery. I installed it and the engine cranked over and didn't start( i expected that because i was told no fuel by previous owner). The TBI was not getting fuel so i replaced the fuel filter. Still no start. I replaced the fuel pump. Still no start; however fuel reaches the injectors. I replaced both injectors in the TBI pod as well as replacing the gaskets. I then found out that there was no spark. Also still not injecting fuel. I'm not a mechanic by the way. The service engine light soon came up on the dash board. I purchased a OBD1 code flasher and it flashes code 12 continuously. NOT 3 times then a code, but just code 12 repeatedly about 14 times then i tried again and it did the same thing. I removed code reader second time and the service engine soon light disappeared and hasn't returned and that was three weeks ago. I then replaced the ICM. Still cranks but has no spark no fuel. I've spent more than i wanted to but I haven't given up and want to get this truck running but i'm lost and this problem(s) are obviously beyond my knowledge. Any help is much appreciated.

 

I think 12 is key on without start.

 

Ya i agree the manual says code twelve means that the ECM code reading function is operational

 

I'm not familar with your code flasher, I know there is a way with a paper clip short the two pins, and count the check engine light flashes.

 

Its he same concept except its a little code flasher that can do the abs system as well.
Innova GM OBD1 code reader 3123 - Read Reviews on Innova #3123
Auto zone link to the exact code reader i own.

 

All you're getting is 12?

 

Yes and i don't understand why. The service engine light hasn't come back on though so maybe just a glitch?

 

The code 12 is normal .. If it repeats 12 and then 12 again than computer isn't detecting any faults.. That is a classic no codes sequence display.. The computer doesn't know that there is a problem.. If the truck has a factory tach and it's needle doesn't move when you crank the engine the problem could lie in the pickup coil in the bottom of the distributor.. If so, a new distrib assembly would fix it.. However a bad Crankshaft Position Sensor could cause that too.. The computer needs to see a signal from both of them in order to calculate fuel injector pulse and spark advance... If you replaced the distributor and the Crankshaft Position Sensor, it should bring back spark and fuel injector pulse if the computer and wiring harness is all in good shape... I hope this info is helpful and good luck.