If you've been following me lately.. well I still haven't got my electrical gremlins worked out.

stock '94Z28

Everything but the pcm ign. and pcm bat fuse are unplugged. Everything in the fuse box underhood is removed. When you first turn on the key the car will do it's normal fuel pump prime and everything else it does.. then the problem is that it will keep doing it and it will not do it completely or not stop doing it. Normally the symptoms are exactly like if it were in the ignition switch.. I know that's not the case though because I get constant voltage while it's happening at the pcm ign fuse which feeds right off the ignition switch. Other people mentioned the vats module.. but I had that bypassed and still nothing.

I've checked everything I can imagine now and I'm no further then when I started. I just need more ideas on what this could possibly be.

Also, if I remove the pcm bat fuse it stops resetting.. I guess because the computer can't reset....or if I remove the pcm ign fuse. So I'm guessing it's likely a ground on the pcm? I don't know what else since I see constant voltage at the pcm ign fuse even when it's happening. If a ground is messing up then I suppose that would reset the computer.

SlowPoke Rodriguez tried to explain a little how to test that.. but I didn't follow. So I guess if anyone knows how to test all the grounds on the computer that would be helpfull.

Thanks,
Ross

 

Now it almost consistently runs the fuel pump and the rpm gauge bounces all over the place when I turn the key to on.

I just wish I even knew what would cause that to happen.

I looked up which wires are grounds and power to the pcm. I pulled the connectors off the pcm and measured the voltage from various power wires to grounds on the other connectors and kept getting 12v on everything.

I just don't understand this problem and so when I try something I don't even know if I'm getting the right results.

I also tried disconnecting the negative terminal and measuring the resistance to ground from the positive in case the main wire was shorting to ground.. but nothing there.

Anyone have any more ideas? It's been a week and a half and I'm nowhere on this.

Details on how to check something would be great because I keep trying to check things as best as I can figure it should be done but I don't really know for sure if I'm checking everything properly or what numbers to expect.

Even just a solid reason what could cause this would be helpfull now as I seem to just be testing random crap without even knowing if it has an effect.

Also, on the black connector.. the two gray 5 volt reference wires...where do they get 5v from? Should they read 5v when the key is on but the connector is not connected to the pcm? I don't think either were showing any voltage. Would that cause a problem like this?

 

I'll be working again tonight on the problem if anyone has some more suggestions let me know. I'm going to try using paperclips to backprobe while the connectors are on the pcm so I can be sure it's happening while I'm checking.

I'm going to try and check the starter wires too.

Are there any other wires I should check on the pcm besides the 4 power and 4 grounds that might cause this weird situation?

OK... it looks like "maybe" the heavy power from the battery and possibly the ground has been rubbing the frame. I'm going to replace those with a spare I have and see what happens......nope that wasn't it

 

UPDATE:

It's not acting up at the moment so I can't verify if this is it....but

I'm getting about 60ohms resistance to ground on the C32 black/white ground wire to the pcm. That's not right is it?? If it's got a little resistance now then I wonder if a little more would be just enough to trip the computer into resetting over and over.

So my question is two things.. is that normal and where does that wire go to? It doesn't happen to be the one passing through C210 connector is it?