'90 RS 3.1 just died while driving.
fuel pressure 39-40 psi.
changed coil wire, dist. cap, ignition module, unplugged a spark plug wire plugged in a skark plug and verified there is spark. I have a digital timing light that when connected to the coil wire will flash when cranking, can not get it to flash when hooked to plug wire?
Will start and run on starting fluid as lond as I spray.
Checked resistance in injectors, 5 about 13, 1 was at 10.8 changed it.
Verified that there is 12 volts to injector harness on both pink/black wires.
Checked all fuses.
checked for trouble codes, 12, 12, & 12 was all that was shown.
I don't know what to do at this point, Could the ECM be bad? or do you have any suggestions?

 

Hook up a 12 volt light across the injector terminals. Crank it and see if it pulses. My guess would be no.

Do you have an oscilloscope?

 

sounds like fuel probs.. Fuel getting to injectors?

 

If these are the stock Multec injectors then they are all bad. They may or may not be causing the no-run issue. As the injector coils short out the ECM injector driver has trouble activating them. This gets worse as things heat up.

If the test lamp across an injector doesn't blink (while cranking), then unplug all of the injectors and try again. If it now blinks the injectors are gone. If it still doesn't blink it can be the ECM that is bad.

Also note whether the fuel pump starts to runs again when cranked. If not then the ignition module or wiring between it & the ECM may be bad.

RBob.

 

I guess I know what I'll be doing again this Saturday
For checking the injector pulse, will a test light do? If I get a Scope to use on it, can someone tell me what the pulse duration should be for the starting sequence?
Thanks,

 

OK, I unplugged one injector and used a test light.
The first thing I did was to attach the clip of the test light to the motor (ground), turn on the ignition and checked the pink/black wire for power, light on power good, then I moved the probe end of the test light to the other side of the plug and found that there is voltage there also, I was not expecting this, is that normal? I would think that it is floating and that the ECU provides the ground? I proceeded to plug one side of the test light into one side of the plug and the probe into the other side, cranked the motor and there was no indication of a flicker on the test light.

 

The other injectors are providing +12 volts to the ECM side of the harness. If all of the injectors are unplugged then you shouldn't find 12 volts there. Only on the one pin of the connector.

Since you aren't getting pulses, did the fuel pump come back on? This is important. Because if it didn't then the ECM isn't getting or it isn't seeing reference pulses from the ignition module. Without them it won't fire the injectors either.

RBob.

 

Hey,
I had similar problem the other day and I dropped down the ECM pulled out the Prom then put it back in.After that I disconnected the battery the did the computer re-learn thing,now it seems to run just fine(for now)...Maybe give it a shot ,all you have to lose is time..

 

If I am checking the correct relay then yes the fuel pump relay does turn back on when cranked. I am checking the inner most relay theat is on the driver side firewall, when i turn on the key it energizes then turns off after about 5 seconds, when cranked it turns back on and when I release the key it turns off after about 5 more seconds.

 

I replaced the ECM, no help. wasted $100

 

Did you ever figure out the problem? I'm curious.

I may be needing to change my injectors because of a similar problem. The only way my engine will start is if the injector ground (don't know which of the 2 injector grounds) at the ECM is manually grounded. Seems to run and stay running and most of the time will even restart on it's own after that ... for awhile anyway and then it does it again. I think my injectors may be shorting out.

I'm afraid if I just replace the injectors that it still won't fire unless I manually ground the ECM to reset the injector controller but I'm kinda sketchy on that thought.

 

It appears that I had a bad coil, even though I showed that it had good spark when I pulled a wire and plugged it in to a grounded spark plug.
$30 later for the coil, not to mention ECM, wires plugs, ect. Still running now.