No start, no spark- help with wiring?

[CoreyB]

Read up, already have done that with a '91 SL to be specific, thanks though will try again. lol

This made me think you must be a 91-92. If you are 93 though the crank sensor is located behind the crank pulley.

Damn time traveling. I need to stop hanging out with those little green people. Always playing tricks on me lol. Real first post is below mine.

[onyxice]

The only reason I'm really making a thread for this is because it's intermittent, at first if I would let the car sit, it would start after a minute. Then over time it turned to moving the harness connecting to the PTU would make the rear bank of injectors "click", after doing that it would start. One day the "sweet spot" for the wiring had somehow moved to the larger bulk wiring down closer to the trans. and that time they fired very rapidly. After that it wouldn't start, my PTU was bad but not the reason it wouldn't start, replaced that, actually ran decent for a weekend (had the wire issue once more) and now it's sitting again, moved every damn wire in the engine bay and not a single noise, no luck anywhere. Not getting any spark, I'm just not sure which wire's should send which signal. In the downtime of not knowing what to do about the wiring, I'm swapping/checking ECU/PTU/thermostat/various things that needed attention due to age anyway.

Any help is very appreciated, been dealing with this for a few months now. No intentions of giving up but it's starting to annoy the piss out of me, and I miss my car. lol

[Austin@STM]

First thing is peel back the tape and look at the wires, if you had to wiggle them to get connection then they are broken or corroded somewhere, or shorted to something.

[onyxice]

I know what that means and how wires work, thanks though. More so wondering if anyone knew which one's should be supplying power to the PTU or from the ECU so I can test with a DMM (Digital Multi-Meter) without tearing my harness apart. That's a lot of tape and wire shielding to tear off accross the area of affect when I moved them. If that's not the issue I'd rather not tear it apart to be left with a taped n chopped engine harness.
Also (just remembered) when I replaced the PTU the fix to start it that time was to clean the corrosion off of the wire that connects the small cylinder on the end of the coil pack assembly, which I believe is an isolator? The plug ended up falling off though, the wires just broke at the crimp one after another, it's jumped with a straight wire now, twisted and taped until I get it back home tonight to use actual connectors.

[CoreyB]

That little canister is a condenser. It absorbs high frequency so it doesnt enter the cars electrical system. Without it you may hear some noise through the radio. Wiggling the wires to the PTU should have no effect on the injectors.
If you want to measure the signal from the ECU to the PTU do this. Disconnect the larger of the two connectors at the PTU, Using a prefferably analog volt meter connect the positive terminal to the pin that would be closest to the center of the PTU if it was plugged in. Connect the negative lead of the voltmeter to ground. While the car is being cranked the needle on the voltmeter should bounce up to about 3 volts and back to zero constantly as long as you are cranking. Thats testing one of the 3 signals. Now test each of the 2 pins next to the first one for the other 2 signals the same way.
The signal is a 5v pulse wave, when the ECU sends the 5v signal a transistor in the PTU grounds the primary windings on the coil. This colapses a magnetic field wich induces a current in the secondary windings of the coil realising the high voltage to the spark plug.

[onyxice]

Just got the car back home so if I don't have time to do those tonight I will tomorrow after work, and I've got an analog as well, actually bought it specifically for the car (CEL codes). lol
However any input to the over all problem is helpful and very appreciated, that being it won't start. If the PTU wiring should have no effect on the injectors then I'm guessing that the problem is somewhere else in the wiring, but I can't replicate that anymore, either way it's still not sparking.

[CoreyB]

You may want to check the contacts on the ECI fuse under the hood. They tend to get corroded and cause issues. What do you hear the MFI relay do when you first turn the key. This is the cycle you should be hearing.
Key on to run = 1 click frome relay
Turn over engine = Hear another click, for fuel pump
Turn key of = after about 10s you should hear a final click.

[GTwizard]

Our wires are old. And they were crap to begin with. The wires ar oxidzed, but you can make some simple repair. Just use Asid flux when soldering to old wires. The acid brakes the oxidation and cleans the wires. Pulling the bundle apart to look for bad spots can be a pianfull Job to most. The main harness has what I call the Mitsubishi Braid. If you cut and un-braid the lines first, you can really change the path of part of the harness, the lengths, and their location. I try to route lines so they will end up a bit more hidden. I run no wires across the front of the engine and as many behind the motor as I can. Not hard to do. Just takes a bit of time. I also hard wire the rear injectors just like the fronts.

[GTwizard]

Not sure if he is first or 2nd gen? Did not say. But never heard of a 2nd gen having Cap issues. Only 1st gens, Just an FYI. The service/repair manual is a must for most any electrical issues. In fact cake with the manual. No harder than making toast. Just takes a little longer.

[GTwizard]

No. You are wrong about that totaly. Yes, all cars get old and thing can go out. That is not the case with the first Gen cars at all. Do your home work dude. The specs for those caps on the first Gen board were correct. But the board supplier never followed those specs and used cheap as infearior parts. Strait up wrong parts on the boards. This was a manufacturing issue from the supplier and this was corrected before the 2ND gens were out. That is the issue.