Seems the usual problem now that I've searched and read hundreds of "Won't Start" posts. My 91 Gen1 LWB cranks it's little heart out but won't start, no spark at the coil. I've verified that the ECU is getting power, terminal #110 according to my service manual.

The ECU tech article (Tech: Troubleshoooting the EFI system in the 3.0l V6) states that the voltage across the test terminals will swing up and down even if there's no fault code and that it swings up and stays up if the ECU itself is broken. Mine has no voltage at all across the test terminals, I even whent out and bought a super cheap analog meter thinking that my digital multimeter wasn't responding fast enough or was trying to average the voltage. I pulled the ECU expecting to find oozing or swollen capacitors but no, it looks perfect! Also the Engine light DOESN'T light up and I'm guessing that's also controlled by the ECU.

As you can see I've already convinced myself that the ECU is bad, it's just that the forum tech bulletin specificaly mentions that a bad ECU will show 12v across the test terminals. Of course being an electronic device I'm sure it could fail in any number of ways probably including flames!

There's one more thing that I should mention that I can't believe contributed/caused the problem but seems statisticaly unusual, the very same morning of the break down I rotated the tires and installed KYB Gas-Adjust shocks (thanks for that post too!). The truck started up fine afterwards and (of course) carried me far from home before breaking down! <img src="/forums/images/graemlins/angry.gif" alt="" /> I mention this only because it seems odd that the same day I did a repair it broke down.

So.... It's my ECU, right??

Thanks,
Bob

I am right where you are. Can anyone verify if this is a bad ECU?

Seems that we will have to help each other out! Here's what I did today, I sourced the 3 capacitors that usually go bad from a local electronics shop and replaced them using these instructions - http://www.tmo.com/howto/ecu1g/caps.htm

Same thing when I put it back in the truck, no voltage at all accross the test terminals. <img src="/forums/images/graemlins/frown.gif" alt="" /> So I boxed the ECU up and sent it FedEx overnight to these guys - http://www.autocomputersupply.com/ . They were recomended in another post. I spoke to them on the phone hoping to get a unit mailed out immediatly but they didn't have any exchange units, they'd only be able to repair mine. They offer 1 day return service so I'm crossing my fingers that it can be repaired. The board itself looked perfect, I've read in other posts that folks have seen burn marks in the center of the board... yikes! I was told that they have a Montero right there that they use to check the units out! I sure hope that they can do more than just replace the capacitors, I've already done that and it took $3 worth of parts and about 20 minutes of time.

I'll post again tomorrow after they give me a heads up if it can be fixed or not.

Bob

Thanks Bob. If it works for you, it might work for me if my board is bad.

yall sure that its not the power resistor thingamajig? that went out on mine and i had no idea. i also had no spark.

Update... It was the ECU and the vendor in my second post was able to repair it (overnight FedEX to boot!). It's running perfectly now.

For those that might wander into this post at a later date I'll answer my own original Gen1 ECU question: If there's no voltage output of any kind at the ECU test terminals with the ignition switch in the on position (and you've already verified that the ECU is getting power) the ECU is bad and needs fixed. I think it's also true that the ECU directly controls the Check Engine light, if it's not illuminated when you turn the key to on (and the bulb is good) then again, the ECU is bad and needs fixed. Finally, the ECU controls the power transistor that triggers the coil, if you have no spark at the coil I'd immediatly check the ECU.

It may be true as the Tech article states (Tech: Troubleshoooting the EFI system in the 3.0l V6) that if the test terminals go to 12v and stay there that the caps are bad and need replaced but I now know that no voltage at all is a problem as well (and possible not fixed by replacing the capacitors).

Bob

Bob, what was the cost to fix your ECU in total? <img src="/forums/images/graemlins/lol.gif" alt="" />

$250.00 for the repair and $35.00 for return shipping via FedEx overnight. They offer cheaper return shipping options if you aren't in a hurry.