Help! Injectors not firing

1988 Isuzu I-Mark Turbo with Geo Storm engine swap.

I used the Storm harness, and therefore had to re-wire things.

Items affected: -injectors -TPS -MAT sensor -Distributor -Coolant temp sensor -Idle Air Control

I have done continuity tests back to the ecm to confirm proper wiring and connected a noid light - but it doesn't light up.

Is there a situation that the computer would see that would tell the injectors not to fire?

What RPM does the scan tool show when your cranking?

Computer doesn't see any/enough RPM when cranking?

Computer not connected to power that is live when cranking?

Computer interpreting TPS as being at WOT, thus going into anti-flood mode?

Crank/Cam sensor not connected/broken/sending signal compute doesn't understand? (oh. Distributor. Uh. I dunno if you have those things)

Is there a relay for the injectors? Is it working right?

GVX19 wrote: What RPM does the scan tool show when your cranking?

-- I don't have a scan tool (and I don't know if a computer this old would show such a signal if I had one) But the rpm gauge does bounce as I crank.

Computer doesn't see any/enough RPM when cranking? --possible

Computer not connected to power that is live when cranking? -ECM has power

Computer interpreting TPS as being at WOT, thus going into anti-flood mode?

--I thought this too. But according to my manual, the best way to check this is to unplug it. I unplugged it - and same result

Crank/Cam sensor not connected/broken/sending signal compute doesn't understand? (oh. Distributor. Uh. I dunno if you have those things)

--I THINK the signal is reaching it (rpm gauge bounces)

Is there a relay for the injectors? Is it working right?

--yes I have voltage to the injectors - the ECM just isn't grounding them.

Do you get a prime squirt? That would tell you if the ECU is able to communicate with the injectors. If yes, then you find out why the ECU doesn't think the engine is spinning. If no, then you know the problem's between the ECU and the squirters. Don't forget to check the 12v power feed to them as well.

Keith Tanner wrote: Do you get a prime squirt? That would tell you if the ECU is able to communicate with the injectors. If yes, then you find out why the ECU doesn't think the engine is spinning. If no, then you know the problem's between the ECU and the squirters. Don't forget to check the 12v power feed to them as well.

I get nothing. I put a test light at the injector output, on the back of the ECM and don't get a signal change to ground.

I have also replaced my ECM

Does the ECM show any signs of life? It's too old to have OBD-II, but it probably has some sort of communication. Does the CEL light up with the ignition?

It should probably have a constant 12V and a switched 12V. If it's got one but not the other, that'll be a problem.

Always start looking for a "no injector pulse" problem by checking the ignition system first. No ignition trigger means the ECU has no idea that the engine is turning, so why would you need fuel?

You'd still get a prime shot in that case, though.

True enough, in most cars. I've sure seen a lot of people chasing fuel problems when they actually have no ignition pulse, though.

Do you have spark?

dean1484 wrote: Do you have spark?

Yes, I have spark. the car will start if I manually apply gas with a squirt bottle.

I can only assume that each of you are correct and that my ECM is not receiving a signal from the distributor (But I do have a bouncing tach at start up, and this leads me to believe that a signal is present)

as a side note, when I put a test light to my distributor wiring terminal labeled bypass, the fuel pump primes and I hear the injectors pulse once.

I will check the signal to confirm

f6sk wrote:

dean1484 wrote: Do you have spark?

Yes, I have spark. the car will start if I manually apply gas with a squirt bottle. I can only assume that each of you are correct and that my ECM is not receiving a signal from the distributor (But I do have a bouncing tach at start up, and this leads me to believe that a signal is present) as a side note, when I put a test light to my distributor wiring terminal labeled bypass, the fuel pump primes and I hear the injectors pulse once. I will check the signal to confirm

will it then run ? or only start ?

In reply to wbjones:

Only start

It seems that the tach signal is separate from the ECM signal, and I cannot therefore say that the ECM is getting the dis. signal. I attempted to put a test light on the back terminal of the ECM, but got no result. I'll try again with a multimeter.

Yeah, I'd guess that in older systems the ecm works get a signal and then the tach would run off of its own signal from the distributor.

Without a wiring diagram I don't know, but does the ecm look for a crank or cam position sensor or is it just reading the tach signal? Is it possible that the format or whatever of the signal that the engine puts out isn't what the ecm expects to see? (I don't remember which parts parts were which)

f6sk wrote: In reply to wbjones: Only start

I figured that was going to be the answer…. without going back through the previous posts … if you pull a (all) the injectors, and try cranking, do they squirt fuel ? is there power to the injectors ?

In reply to wbjones:

they do not squirt. there is nothing at the noid light. There is power to the injector but it never gets grounded. I'm wondering if I may have a bad module

Found the problem! GROUND WIRE!

Grrrrrr. I checked for this and even added additional grounds, but there was one that I missed and this was it

http://m.youtube.com/watch?v=uO-icsfKBAo# got it running