Injectors not firing; ECU problem?

[FastWoman]

I think you've covered everything. Your pin 10 seems to be the + supply to the ECU, and you've confirmed the ECU grounds. Your pin 1 is good, and yet when you cycle it between +12 and gnd, there's no injector pulse. I'd say your ECU is dead. I don't see any other possibilities, although others here might have some other ideas.

[Lani Kai]

Oh right, 10 is ECU power.

[Zed Head]

Yes, it does look you've covered all the right tests.

You might try to figure out why the CSV is on all the time, or run the tapping test without it connected (Edit 2 - looks like you've already done that by trying to run the car without it). I know the ECU has a CSV circuit, but can't remember how it works, I think that it only gets power at Start. I wonder if the CSV was shorted externally to the ECU, if it would cause the ECU to stop firing the injectors. Just a thought. You could unplug the CSV to remove the power and try the tapping test again, or check the CSV wiring for shorts. Check at the ECU pin to ground from the CSV pin, key Off.

But the CSV spraying all the time and the injectors not firing is not a good sign for the ECU.

Edit - if the CSV is on all the time, it seems to imply a short in the ECU or the ignition relay. If I understand my own notes, the CSV circuit in the ECU only gets power through the ignition relay during Start. But I don't know if it's a separate circuit to Pin 21 or if Pin 21 is a branch off of another ignition circuit. Worth a look. Check Pin 21 for power with the key at Run.

Note that these are off the top of my head. The FSM wiring will tell you the CSV works in detail.

Edited June 23, 2012 by Zed Head

[Wade Nelson]

>Cold start valve is also having problems (always has). It's constantly getting a current and keeps continuously spraying fuel. Previously, when the injectors were working, I had unplugged it because I don't really need it. Right now, the only way the car can start is with the cold start plugged in (the car is running on fuel from the CSV only)

If your CSV is constantly being fed current then your ECM thinks your engine is constantly being cranked. Check your crank signal to the ECM. You might just have a bad keyswitch.

[Lani Kai]

Well, I went and bought a new ECU, and the car started up right away with the CSV unplugged, which is something that I've not been able to do in a long time. I also tried the Christmas tree light test and confirmed that the injectors are firing at regular intervals.

However, after running for about 20-30 seconds at idle, it just died. After that it started once and died again, this time for a shorter period of time. Now it just cranks and cranks and doesn't start, although I suspect it might be flooded. I'm going to let it sit for a while.

In the meantime, I guess I now need to consult the section on troubleshooting for "starts then stalls"?

[Wade Nelson]

You'll need to consult the the schematic of the EFI system in the factory service manual to determine which ECM pins should have continuity to ground, B+, etc.

If you don't have a FSM or know how to read schematics, you'll want to hire someone who does. It's not really something you can expect someone on a forum to do for you.

Since you've previously had CSV problems, I'd be paying special attention to those inputs to the ECM, thermotyme, crank signal...

Most likely you have a shorted sensor, putting B+ to an ECM input that shouldn't be seeing B+, or else one of the ECM outputs, like an injector driver, is shorted to ground. Those are the most common ways an ECM gets "confused." Since your "new" ECM lasted 30 minutes, I would check the resistance of my injectors, make sure one isn't shorted.

Good luck, and if all else fails, I can drive out to OC and diagnose it for you. But I expect you'll figure it out long

before that point, or find someone local to help you who's good with auto electrics.

I'd also unwrap my ECM wire harness and look for wire damage, rodent damage, previous repairs, melted wires/insulation, green corrosion in the connector, etc.

[FastWoman]

Interesting! I wonder whether you still have drop resistors, or whether someone simply removed/bypassed them, thereby overloading the injector driver circuits, as Wade suggested. The drop resistor assembly is located beneath the brake master cylinder. It would be a good idea to measure the resistance from + to each of the ECU's injector connectors. I forget the resistances of the various components, but I think I recall the drop resistor and injector both being about 2.5 ohms (each -- i.e. 5 ohms in series). I could be wrong about this, but I think all you need to confirm is that they're somewhere in the general range of correct.

I'm going to throw out another guess: Maybe your alternator is going bad and blowing out your ECU. How is your system voltage? Is there a noise suppression capacitor connected between the alternator + post to ground? Of course since your car isn't running, it's hard to determine these things. Maybe you could pull your alternator and have it tested at your local auto parts store. If something is killing your ECU, I would think that's a likely cause.

Edited June 26, 2012 by FastWoman

[Lani Kai]

I think there's been a slight misunderstanding. While the engine started and stopped running, the new ECU is perfectly fine. It still lights up Christmas lights as if it were December, so I don't think it's been fried or anything. My current problem lies elsewhere.

[grantf]

Got Gas? not trying to be funny. just asking.

[Lani Kai]

Yeah... So I was just going to post that...

It was indeed out of gas.

Now it runs pretty strong but needs some timing work. Also runs pretty rich.

Edited June 26, 2012 by Lani Kai

[Willoughby Z]

Got Gas? not trying to be funny. just asking.

[Lani Kai]

Also, I just removed the old ECU from the car (previously, I hadn't bothered removing it from the bracket while I tested the new one).

Carved on the back side of the ECU with a knife or something was the word "BAD"

I wish I was making this up.