rodie_27

I've looked and looked to find a similar problem on here but just can't. When I bought my '89 IROC, I didn't know there were electrical issues. Anyway, one wire, I believe a black/white, coming out of the ECM connector going to the driver's side firewall fried, melting a bunch of other wires to it.
I spliced in new wire for all those affected and car ran great for a couple days until issues began again. I want to do everything right. So I'm hoping you can maybe point me in the right direction as to what the wire is for, why it got hot, and what I need to do to fix it, i.e. new harness, new ecm, etc.
In addition to the story, I had it towed to a shop and the guy was nice enough to clear the security codes for free, but didn't want to mess with the wiring issues, said the injectors weren't getting juice. Dash is completely removed, so I have unrestricted access to ALL wires.
Please let me know if there's any more information you might need, just trying to keep post as short as humanly possible.....thank you for your time.

BigBadLou

iTrader: (3)

Howdy,
you got my attention with the title, bud.

If you tell me which terminal on the ECM the black/white wire comes from, I can hopefully tell you what it does (but it's usually ground).
But I don't think that will help you much. As with all wiring fires, it's usually not the wire that caused the problem in the first place but the other wires whose insulation got melted and now they're toughing each other or ground.

As you said, you fixed the one bad wire and all worked fine for a while but now you're having issues again. That's exactly the main symptom of fried wiring in the clusters.

Sorry but my only advice at this point would be to replace the whole underdash wiring. Yes, it can be an involved job but hey, you only have to do it once and it will all work. Because if you just go replacing wires one by one as they keep popping up, you'll pull your hair out.

So many people here have spare harness from an '89, you should not have a problem swapping it.

Oh, I wouldn't think the ECM is bad. If it ran fine recently, the ECM seems good, it's just the wires that are "acting up".

Lou

rodie_27

Hey thanks so much for getting back to me. I will hopefully have a chance sometime this week to take a look at it some more and get back with some good info. Could it be just as simple as a bad ground? The whole car has had ground problems, I've had to replace the front light harness, the tail light harness, and need to repair both the engine and dash harnesses a little better. I've fixed lots of grounds and think that maybe if I just take my time and repair everything it could possibly work. I did buy another dash harness on ebay to switch but after pulling the connector apart on the firewall found out they were different. Oh well, now I have a duplicate of most everything else. But like I said, I greatly appreciate your help, you're truly a priceless asset on this forum!!! I'll see what I can do later this week and get back to you.

rodie_27

Are you there Lou (or any other electrically oriented individual lol)? Sorry I took so long to get back on here but Illinois has had some crappy weather for a while! That together with my new job and night classes.....whew! Anyway, I got my harness repaired again and hooked up. I charged the battery and got it to turn over but not start. The first time, the fuel pump primed and I think I got one or two ignitions but additional cranking didn't produce any more results.
The second time (a few hours later) the fuel pump didn't prime but the starter cranked. After a few times turning the keying the starter on and off, I discovered the fuel pump would run while cranking and shut off shortly after. But it would never prime on key 'on.' Could this be a passkey issue? Could I have thrown some codes disabling me to start it? Hopefully we have good weather tomorrow and I can check it out again. Any insight is always appreciated!!! Thanks in advance.
Tyler

BigBadLou

iTrader: (3)

The fuel pump is not controlled by the VATS. Once again, VATS does NOT control the fuel pump.
The priming is done solely by the ECM, for 2 seconds after you turn the key on. Then when you're cranking the engine, the oil pressure builds up and the oil pressure switch turns the fuel pump on. Once you stop cranking, the oil pressure drops and fuel pump stops.

You need to wait 15-20 seconds with the key off, then if you turn it on, the fuel pump should prime again. What I'm saying is that if you turn the key on, off, on, off, on, off, etc, the fuel pump won't prime every time. It primes only after the ignition has been off for 15-20 seconds.

As for the no-start, can you smell raw fuel from the tail pipes after long cranking? If yes, it's not a fuel problem and thus not a VATS problem (VATS disables injectors). I'd look for spark.

If you cannot smell gas, squirt some starter fluid or brake parts cleaner (something flammable) into the intake and crank the engine over. If it fires up and dies, you do have spark but not fuel.

Let us know what you find, we can take it from there.
Lou

rodie_27

Wow, thanks a lot. I'm just about to go out and see what I can see. Thanks for the simple yet ingenius tests! Not sure why I didn't think of that. Thanks Lou!!!

rodie_27

Thanks for the help Lou!!! I finally got my car started the other day and had it running pretty darn good tonight! First time in 4 months. Still need to replace my fuel pump relay, it's going intermittently. She didn't want to stay running when she was cold though. When it finally killed choke she ran real nice. Brand new idle air control and O2 sensor. Any suggestions? Also, what is the connector that looks similar (identical?) to the O2 sensor pigtail? I have a lonely one, whatever it is. Thanks for all your help Lou, your information and input have been understatedly vital to me!!!

BigBadLou

iTrader: (3)

Glad you got her running!

What is the wire color for the lonely connector? What's its location? If you have a camera, a picture might help.

Lou

rodie_27

Hey Lou thanks! It's about time I got 'er! Ok, I won't have a chance to get a picture of it, but it's a green wire toward the back of the engine compartment. It appears to be coming from passenger side to driver side but not overly long. I'll be in Florida for a week on spring break so don't worry about rushing. I suppose I'll have a few hours to read over my Chiltons manual on our flight lol. Well, I always appreciate the help and comments!

BigBadLou

iTrader: (3)

That's what I thought, a dark green wire. It connects to the temperature sender between the first and second spark plug on the driver side. It shows the engine temperature on the dash gauge. If disconnected, the gauge needle is in full red.

Lou

rodie_27

Ok, I got a chance to look at my car again today and found that the lonely connector is on the rear drivers side right behind plenum. So this one isn't the temp gauge sender. I just replaced my sender so I do know that. It has the same exact connector as the O2 sensor and is a green or dark green wire. I have no idea where it plugs in, I'm thinking it might be the EGR temp wire? Also supporting my thinking, my car does not at all like to stay running while it's cold. My buddy mentioned that a lot of cars run the choke off the EGR temperature. She runs like a bad man once warm though!
Another problem keeping me from putting my dash back together is suddenly my headlights aren't working. I didn't have a multimeter at the time, so I'm not sure of very much. All I know is that when I parked it, the lights worked fine. Where should I start? Definitely need to get that figured out before I do all the hard work. Thanks Lou!

deadbird

This is not correct (unless your fuel pump relay has stopped working). The oil pressure switch is a failsafe to the fuel pump relay. The oil pressure switch is not even needed in the system for the fuel pump/relay to operate.

BigBadLou

iTrader: (3)

Correct. If the fuel pump relay works (which we assumed didn't), then it turns the fuel pump once the ECM detects pulses from the distributor which usually happens before the pressure builds up.

So since the fuel pump relay was an issue here, I was explaining how the back up oil pressure switch works, without the help of ECM.

Rodie, sorry, I have no idea what that wire might be. Did you check every single sensor and are they all plugged in? No other connectors left unplugged? It's a real mystery.
Does the wire maybe have an unnoticeable stripe of different color? These old wires are usually so dirty and faded that it's not easy to tell. My car is the same way.

Lou

rodie_27

That's allright. I'm sure it's a green color with no stripe. It has a very short pigtail, about 5-6 inches coming out of loom. Anyway, my bigger concern is finding a new headlight switch. I did some continuity tests and I'm pretty sure that's what's keeping my headlights from working. Oh, another question, do our cars have a headlight relay? Kinda small and squarish? Hopefully once I get my lights working I can put my dash back together! Thanks Lou.

BigBadLou

iTrader: (3)

No headlight relays on our cars.
The only relay connected to the headlight circuit would be the fog-light relay.
No idea on its shape, though. But I could identify it by wire colors!

Lou

rodie_27

Well, good news and bad news. I finally got my lights working, albeit by sacrificing my parking lamp capability. Jumpered headlight lead to parking lamps/tail lights. After that I started putting my dash back together, except for mounting all the modules (fuse block, VATS system, convenience panel, ECM, etc). So I was wondering if you might have a picture or other method of figuring out where all that mess of wire goes! In my haste to tear apart last year, I didn't memorize or otherwise pay attention to where stuff went
Besides all that, I was running my car last night and found a disconnected vaccuum tube to be the source of my erratic idling. However, it was to be short lived. Soon thereafter, smoke began coming up both sides of engine so I shut it off. I look under the car and coolant is spewing out the back of the driver side of the block. At first I thought head gasket or cracked head but I think it's just the freeze plug. Might you have any thoughts as to the source of problem or fixing it? My buddy has an uncle who can, just wondering if I might be able to do it myself. Sorry for the long post.....