Is my ECM bad? (81 carb'd converted to 88 HO)

[ratio411]

I converted from carb'd I6 to 88 HO EFI...
I transplanted everything from the donor car straight over.
Wiring, fuel tank, relays, etc... all as stock.

All I really had to do was hook up the constant hot wire, grounds, and I used the 'key hot' wire from the Duraspark so that the ignition would stay energized even when the starter is cranking. Oh, and the starter activation wire had to be tied into the harness too, for the later model ignition module.

I have yet to put gas in the car and try to start it in earnest, but I have it ready otherwise.

I did a dry run this evening, and turned the key to cycle the fuel pump, however, it didn't cycle. I checked the relay and it is good, as is the fuel pump.
The constant hot is hot at the relay, and the ECM hot trigger wire comes on with the key. The only thing I can figure is the ground that the ECM uses to cycle the pump is not working... Therefore my suspicion of the ECM. When I manually ground the trigger, the fuel pump comes on.

Next issue...
When the engine cranks, there is NO spark.
HOWEVER, when the key is released from "start" to "run", the coil wire sparks while the engine spins to a stop. Make sense?
When the starter disengages, the engine continues to spin for a split second more, causing the distributor to signal one last spark. So if I was trying to actually start it, the engine probably wouldn't start when the key was turned to "start", but might actually start and run when the key is released because spark is triggering in the "run" postition.

What the heck would cause this?

I removed the start wire from the solenoid so the engine wouldn't spin, then engaged the key in the "start" position...
The coil is powered up, the module is powered up, everything seems normal.
It 'should' have spark, unless the spark wire from the ECM is not triggering.

Is there any sure fire way for someone with very basic tools to tell if the ECM is doing it's job? It is pretty obvious that at the very least it is not operating the fuel pump.

IDEAS?

Thanks!
Dave

 

[liljoe07]

You need to make sure the TFI is getting power. #3 wire on the TFI should have power when cranking, and #4 wire on the TFI should always have power whe key is on or cranking. Make sure the ECM ground is not hooked to the positive side of the starter relay. It looks like is should,but shouldn't. That wire is black with green stripe. Remember, its a ground. Let me know what you find.

 

[ratio411]

Check, check, and check on all 3 points.
The ground comes from the ECM through the stock harness.
The red/blue start activation wire was hooked to the stock wire, which was also red/blue.
The power wire is the stock Duraspark power wire that is hot no matter if key in 'start' or 'run' position.
The Duraspark wire is hooked to the green/red wire in the harness.
That wire also goes to the ECM power relay. That relay is functioning, and the ECM sends out VPWR when the relay is triggered.

I am worried I burnt the ECM because before I knew any better, I put the keyed power to the VPWR wiring. I later found that the ECM powers these wires itself, via the black/orange constant hot, after the ECM relay is triggered. When the key was turned while it was miswired, the entire 12v wiring dropped to about half voltage. The test light dimmed to roughly half, or less, brightness when put to any 12v wire in the engine bay.

Now all 12v wires are acting properly.

 

[ratio411]

The ECM has several ground wires that show continuity with a buzz tester, plus the ground strap.

I don't have the ECM itself bolted down yet, but with the extensive network of grounds, I figure it is grounded plenty. Does the case need to be grounded, PLUS bolted down to ground properly.

I put the test light clamp on the case, then probed a hot wire and did fine. I also put the buzz tester on it from case to fender and got continuity. So I don't think I have a poor grounding.

Am I correct, or missing something?

 

[ratio411]

Test light, hooked to ground, will trigger fuel pump when probed to ECM test lead tan/green wire.
Tan/green is the trigger wire to the fuel pump relay. It is a ground switched by the ECM to operate the pump... Should the test light light up when hooked from ground to tan/green ground wire? Seems funny to me that it does. I know it is completing the ground circuit, but to light up???

 

[ratio411]

BUMP...

Apparently the ECM won't switch on the fuel pump.
Does that mean the ECM is toast? Is it serviceable?

 

[InjectorsPlus]

BUMP...

Apparently the ECM won't switch on the fuel pump.
Does that mean the ECM is toast? Is it serviceable?

First off you need to verify powers and grounds to the ECM as follows.

Pin 1 12v power at all times
Pin 37 12v power key ON
Pin 57 12v power key ON
Pin 20 Ground
Pin 40 Ground
Pin 60 Ground

If all of this is GOOD, then check pin 26 for VREF which is the 5v reference to the TPS, EGR position etc.

If you have ALL powers AND grounds, and NO 5v reference at pin 26, you either have a dead ECM or you have something hooked to the VREF that shouldn't be grounding out the VREF, or a pinched/cut/grounded VREF wire somewhere.

Hope this helps.....

Tony @ IP