The old cranks no start problem

[noncarbonated]

thank you for the advice. the injectors are new Rochester off ebay I will get a noid light to see if the ecm is communicating with them. the fuel is fresh maybe a month old. this thing is keeping me up at night! hopefuly this weekend!

 

[dave s]

Exactly. No way to take the computer out. It’s electronic fuel injection.

I should have figured that. So you are just unplugging the same one you unplug to set the initial timing then?

 

[noncarbonated]

Ok got a noid light, its a no go on either injects, no light while cranking. also, if I connect a 9v to the injectors, they will spray the initial priming fuel out just fine. thinking ECM? is there an injector relay perhaps?

 

[Schurkey]

Is the noid light not lit up because there's no power, or because there's no ground?

Power should be supplied through an injector fuse.

The ECM will not ground the injectors if it doesn't get a signal from the ignition system. This is possible even though you seem to have spark--failed wire harness, perhaps.

I'd be looking at the injector harness first. See if one of the two prongs in the connector that plugs into the injector has system voltage (12-ish volts.)

 

[noncarbonated]

ok seems reasonable. I checked the ign and ign a+b fuses earlier with voltmeter both checked good. I'll check ground on harness. man just such limited can't wait to retire. thanks

 

[noncarbonated]

Hey guys! Ok yeah there is 12ish volts at the injector plugs, so I'm guessing that the ecm isnt grounding. Tried a new ECM, still the same show, injectors not firing. Whats the next best step? I cant believe such a simple system has me beat! Thanks in advance

 

[Schurkey]

I'm guessing that the ecm isnt grounding.

Or the wire harness from the ignition module to the ECM is broken.

Tried a new ECM, still the same show, injectors not firing. Whats the next best step?

Connect a scan tool, crank the engine. See if the computer knows the RPM it's being cranked at.

No rpm = no signal from ignition module = no injector pulses.

 

[noncarbonated]

Or the wire harness from the ignition module to the ECM is broken.


Connect a scan tool, crank the engine. See if the computer knows the RPM it's being cranked at.

No rpm = no signal from ignition module = no injector pulses.

Thank you sir will check in the morning!

 

[thinger2]

Have you tried firing it with dist wire unplugged, timing set at zero tdc?
No, disconnecting the dist wire does not take the ecm out of the loop.
It keeps the ecm from controlling the timing.
Same ****** thing.
Semantics.
You dont need to spend a fortune in diagnostic tools just to satisfy some lingering angry gatekeeper.
You need a volt meter, a mighty vac, and a timing light.
And a decent set of tools.
TBI problems are rarely hardly ever a bad ecm unless youve back fed it and fried it.
Bad grounds, crusty wiring, throttle body plugged full of carbon, worn throttle shafts, worn distributor, bad plug wires.
Normal mechanic ****.

Its a small block Chevy bud!
Its easy,
You dont need 4 grand in tools, you dont need to buy an ecm
Fix the grounds, charge the battery, and do the starter.
******* cake.
Do not let anyone convince you that you cant do this or that you can only do it if they approve of your process.
Fuckem.
Dive in, get dirty and drive it

 

[noncarbonated]

Thank you for the encouragement man! So long story short, it was the ICM. I learned a trick from a friend of mine, disconnect the 4 pin connector on the ICM, jam a wire in the purple/white connection, lick your finger and touch the positive battery terminal at while touching the attached wire (ignition on start), the injectors fire. I'd never heard of such a thing. so changed out the "newer" (china) ICM to an old delco one. fired right up. took her for a ride around the block, little bit of hesitation maybe clogged egr or old plugs oh and looks like front main has dried out and dripping oil behind the harmonic balancer. but IT RUNS!! thank you for your support and advice u guys! time to chase down the rest of the gremlins.