Ignition Module??

[Guest Anonymous]

I could use some of your guys' opinions on my car here.

 

Oh boy, where to start!

I have a '79 280zx... the kind with the ignition module on the distributor right underneath the upper radiator hose. Gotta love nissan for thinking that one through!

 

My problems started a while back, when I first started the car when it was cold, it would smoke black smoke, I thought it was blue, but my dad says it was black. If it was black (which I believe him, because I only saw it in my rear view mirror) then it would be an indication of 2 things, one that it was running rich, and/or 2 that it is getting poor spark, and once it warms up the heat helps combust the mixture.

 

Now, that was the first part of the problem, the second was when sometimes my car would not start, but only when the car was hot. Now there were a few wierd things going on there. One of them, was that if you push started it, it would start right up, and run fine. Another was that if I had driven the car, and I had a feeling it was going to not start, I would watch the tempature gauge. It would be normal, right in the middle when I shut the car off. Then, I would crank it, and nothing happened, well, no spark at least, but now, turning the key to the on position, the temp. gauge would read really high, like 2/3 of the way across the normal range, but after push starting it, it would read normal again, I found this very odd...

 

Now a couple of days ago, I was playing with my car, and it died, I don't know what I did, but it died when I moved the main injection wiring harness. Today I was running through all of the circuit tests of the main module, by checking the resistance and voltage on the terminals of the main harness connector at the ECU, as per the manual's instructions, and I came up with a few strange things...

 

1.) My TPS connections seem kind of wierd, the idle contact goes straight from 0 ohms, to infinity once you press the gas pedal a bit, the full throttle contact moves from infinite to resistance, to 0 resistance once the pedal is about 1/4 to 1/3 of the way down. the adjustment there is obviously off. Now I was under the impression that the resistance should gradually increase/decrease, then at a certain level the connection breaks completely. Is this right, or should it jump instantaneously like it is?

 

2.) Now I learned the other day that the pump should not be running when you turn the ignition switch on, and that this is controlled by the AFM, and that someone probably just adjusted the AFM wrong, and now the pump stays on, which isn't too big a deal I don't think?? It just needs to be adjusted correctly.

 

3.) The thermotime circiuts aren't working right, but I think the wire to the thermotime switch is broken, but I usually keep the cold start injector unplugged anyway, and it is nice and warm here, so I don't think this matters.

 

Now I have intermittent weak spark, and a test light to an injector lead also shows an intermittent signal. The engine acts like it wants to start, but never quite gets all of the way there. I am thinking, that if the ignition module is bad, it would explain why before, it wouldn't start when hot (too much resistance), and I'm thinking that when you cranked it, the module couldn't get enough voltage, but when push starting it, it would get a full 12.5 volts, and start.

 

Now I think the module went completely (almost) and now it is sending intermittent signal, to both the coil and the computer, causing both bad fuel and spark.

 

Does this sound right to you guys? any other Ideas?

 

Thanks alot, and sorry for the long post,

Kris

[J Taylor]

I can't help you on the rest of it but the temp gauge should go up when you turn the car off as it is getting no more water circulation. When you start it back up it will drop down very quickly due to the cool water running through the motor.

JT

[DAW]

It sounds like you have more than one thing going on. If you really think you've got an intermittent IC module problem then replace it. If a new one's too expensive then pull a used one in a JY and look for a smashed vehicle like it was being driven before it went to the JY. Also check application, the module is pretty basic and may fit Zs as well as Maximas and even 4cyl Nissans of similar year.

Check the engine harness well. It sounds like you may have a bad, loose or corroded connector to the temp sensor since you get black smoke. DAW

[RB30-ZED]

You say that the fuel pump is running with the ignition on and the engine not running, well it will run for a second or two when you first turn the ignition on, but it should stop. The most likely cause of this and your black smoke problem is the air flow meter sticking in a open position ( mostly caused by a back fire) which will make the computor think it is consuming more air and give you more fuel, hense the black smoke. This will also run your pump all the time as the computor thinks the engine is running, if the AFM was ok you could turn the ignition on and open the flap with a screw driver and hear the pump turn on and off as you open and close it.

Steve