Hey, so I have a '92 camaro rs 305 tbi injection and my injectors won't pulse. I've changed the distributor, changed the injectors about a year ago, its getting gas, its getting spark, and it will crank, just no start. Im really confused on what to do, I've tried to check the ground wires but I cant find them for the life of me, I've checked the every fuse on the car, they are all good. I heard that it could be a faulty ecm but I hope not because those are a little pricey for me atm.

 

Any injector pulse if you pull the ecms prom ?

 

Im not sure, im going to have to check that out tmrw. Thank you for the idea

 

It forces the 1228746 ecm into limp home mode as well as a temporary way to check vats by bypassing it.

 

had that problem on one injector. had power to both injectors but had a funky bare wire in the harness and replaced the ignition control module and taped up the bare wire rf emi tape. don't know which one was the fix. I believe the ignition control module triggers the pulse. pulse is the ground going on and off.

 

1. What is the fuel pressure?
2. Do you have power to the injectors when the ignition is "on"?
3. Connect a TBI 'Noid light to the injector wire harness. Crank engine. Does the 'Noid light flash?
4. Do the injectors click (and spray, IF there's fuel pressure) when you put a new 9-volt battery on the terminals? The injector terminals are nicely-spaced for testing with the 9-volt battery. Don't hold the 9-volt on the injectors--just touch and remove.

Injectors can fail to spray fuel because:
There's no fuel pressure
There's no power to the injector coil
There's no ground to the injector coil
The injector is varnished, the pintle won't move
The injector coil is open, no current flow = no magnetism to move the pintle

I had one varnished injector on my '88 K1500 5.7L. About the time I was wondering what I was going to do about it...it freed-up and has been fine for all these years since then.

The pickup coil in the distributor triggers the ignition module. The ignition module sends an RPM signal to the computer. The COMPUTER triggers the injectors based on the RPM signal, by connecting the injectors to ground. The injectors have constant power when the key is turned to "Run" or "Start".

You can verify the RPM signal to the computer by connecting a scan tool. See if the scan tool shows RPM when cranking.

 

Would he be able to monitor the tachometer while cranking the engine over to verify RPM signal to the computer?

 

Does the tach get it's signal from the computer...or independently from the ignition coil?

 

That I don't know. I was just wondering if it was possible that he could watch for movement of the tach if he didn't have a scan tool.

 

Thinking about it again, probably not. People swap these cars from fuel injection to carb all the time and the factory tach still works without a computer installed.

 

Tach signal comes from the coil, icm sends a reference signal to the ecm that is a tach signal purple/white wire at icm.

 

Anyone performing D-I-Y work on a computer-controlled vehicle needs a scan tool, or scan tool emulator.

Trying to diagnose computer problems with no reasonable way to communicate with the computer to access the data stream and to have some bi-directional control is two steps away from hopeless. Instrument cluster "Blinky-Light" diagnosis is one step away from hopeless.

 

Yeah, it's much easier if you at least have a Snap-on MT2500. They are cheap enough now days.