Easiest way to find a broken wire?

[Bamamav]

Bought and installed a new set of injectors in the Vette crossfire. Still can’t get one to fire. Not a lot of troubleshooting info out there on this ancient system, but I found someone say to swap the plugs from one injector to the other to see what happens. After I checked to make sure I had 12 volts at each plug, I swapped them, the no fire followed the plug, the other one now fired but the other one won’t now. The distributor switches the ground to make them fire, so I’m thinking I have a broken wire or connection somewhere. Without taking all the wires out of the harness, is there any way to find a broke wire or connection without a special tool? Not really looking forward to tracing one wire through the harness.

I’ve got a Edelbrock intake stuck back, if I can’t get this injector working I’ll probably get a new carb and HEI distributor and swap it over.

 

[lowbudget50]

Bought and installed a new set of injectors in the Vette crossfire. Still can’t get one to fire. Not a lot of troubleshooting info out there on this ancient system, but I found someone say to swap the plugs from one injector to the other to see what happens. After I checked to make sure I had 12 volts at each plug, I swapped them, the no fire followed the plug, the other one now fired but the other one won’t now. The distributor switches the ground to make them fire, so I’m thinking I have a broken wire or connection somewhere. Without taking all the wires out of the harness, is there any way to find a broke wire or connection without a special tool? Not really looking forward to tracing one wire through the harness.

I’ve got a Edelbrock intake stuck back, if I can’t get this injector working I’ll probably get a new carb and HEI distributor and swap it over.

If you and reach each end of the wire you can use a multi meter and do a continuity test.

 

[redidbull]

Are the wires different colors? How many wires are in the harness. Do a search for Corvette crossfire groups or community. I am sure there is a group of enthusiasts. There seems to be groups for everything. Jim

 

[Bamamav]

Problem is I don’t know where to find the other end, at the distributor or the ecm. Guess I need to order a good wiring diagram. Really need one anyway, it’s got a direct short in one circuit on the fuse block, lighter, power door lock, power antenna, dome lights are all on the one fuse, it blows as soon as you put one in. Tracing all those out and disconnecting them one at at time will take a while, but that’s about the only way I know to do it.

Just a little work and a whole lot of head scratching . [S

 

[smallfoot]

I use Lowbud's method although it can be a pain!

 

[Bamamav]

Found a little info on the web today. There is a firewall plug connection I need to check. Other thing I found out is it could be the ecm. It’s looking like it’s the trigger ( ground) coming from the ecm since I have 12 volts on both injector plugs. Will probably try a jumper between the two plugs on the ground side. If that works I’ll know for sure it’s the ecm or a connection. If it’s the ecm, I’m still thinking about going to a carb.[S

 

[Tripper]

If it’s the ecm, I’m still thinking about going to a carb.[S

Vettes have a lot of electric problems & I converted the Vette motor in my Nova to HEI & carb & never looked back!

BoB

 

[smallfoot]

When they got ecm and computer use in cars and trucks, I no longer wanted to buy anything "new". Those features turned guys like us that like to take things apart and physically fix things into plug and play idiots. I know, some of the sophisticated test machines will narrow it down pretty good, but the testers are expensive. The sensors involved, the totally enclosed devices are expensive, and you'll go thru a bunch of unnecessary replacement parts in a hurry if you're wrong on your assessment. I know plug and play is sometimes easier but it's just not the same...
Carb and HEI it would be for me too!.

 

[redidbull]

When they got ecm and computer use in cars and trucks, I no longer wanted to buy anything "new". Those features turned guys like us that like to take things apart and physically fix things into plug and play idiots. I know, some of the sophisticated test machines will narrow it down pretty good, but the testers are expensive. The sensors involved, the totally enclosed devices are expensive, and you'll go thru a bunch of unnecessary replacement parts in a hurry if you're wrong on your assessment. I know plug and play is sometimes easier but it's just not the same...
Carb and HEI it would be for me too!.

I agree with not liking the new stuff. The 89 F150 I bought had EFI and OBD1 which is the worse of combinations. I'd love to carb it but the trans is dependent on electronics from the engines ECM to the trans ECM. Just too much work and money for what it is. Jim

 

[Bamamav]

Fiddled with it today. Checked and cleaned the plug at the firewall, no change. Tried coupling both injectors on the good wire, got both to fire that way, but it wouldn’t run but a few seconds, must be overloading the ecm. Put it back they way it was, moved to the inoperative wipers. Can’t get fire to the from inside, so I pulled the fuse, yuk, it was corroded. Spray cleaned the fuse box with electronic cleaner, put in a new fuse, still no go. Hooked my jump box direct to the wiper motor, it would move a little, but the park setting worked fine. Bad motor probably.

Went and got some hose, had a couple of vacuum lines leaking. Fixed those, cranked it up, SOB! Both injectors were firing! Runs great with both firing. Let it run a bit, then the back one quit again. Goosed it a couple of times, it came back alive. Done that several times, it would work a while, quit, then start back. Finally, it quit again and I couldn’t get it to pick back up. After supper, wife got in it, it fired right up on both injectors again. WTF?[S

It’s something electrical. What, I haven’t figured that out yet. From the looks of that one fuse, I’m starting to think this thing sat with the windows partially open and moisture got in. After I cut grass tomorrow I’m going to pull each fuse and clean the contacts with a small file or emery board, then spray contact cleaner on them again. The fuse block is up under the dash, so you about have to stand on your head to get to it.

Not giving up yet!

 

[soltz]

Good Luck [P

 

[redidbull]

Being you were saying the fuse was corroded for the wipers have you taken the ECM out and looked for corrosion on the connectors or even inside? I used to repair ECMs for the Suzuki community and often came across corrosion. I also had an intermittent wire on my Samurai. I was able to wiggle the harness and make it work and not. Started with the whole harness on the firewall and started doing less and less wiggling of the harness and found an intermittent going into a weather pak connector. Jim

 

[Bamamav]

I did, but probably not good enough. The ecm sits behind the seat, so it’s easy to get out, wish the fuse box was there, but I digress…The connectors for the ecm slide directly onto the board, no plug on it, just the flat board in a slot in the cabinet. Why they thought that was a good idea, I dunno. I did spray both the board and the harness plug with contact cleaner, but I was afraid to rub very hard on the board. This ecm board is ancient design, no wonder replacements are almost impossible to find. Fun to try and make work though!

 

[bob w]

A broken wire has four ends.

 

[05snopro440]

I have solved a lot of intermittent electrical issues on GM's by carefully scratching the electrical contacts with a small sharp screwdriver to remove oxidation.

It sounds like you've narrowed it down to something in the injector firing circuit. Is there any way you can bypass each harness wire (power, ground, whatever) with a jumper to try to pinpoint your issue? I'm not talking jumping the injectors as you've done, but seeing if it's in the harness by jumping back to the ecu. A power probe could do it, but those are expensive.

 

[Bamamav]

Snopro, you hit on exactly my next action. This morning, it started fine on both sides, then it got to cutting in and out again. I dove into the fuse box, pulling fuses, spraying the contacts with CRC contact cleaner, replaced a couple of fuses with new, others I scraped with my knife.

So far, it has worked! Got my interior lights to work, my wiper and washer now work, and the engine hasn’t cut out a single time. I knew it had to be electrical, but finding it was the problem. CRC is the good stuff!

Going to take it down the road in a bit and see how the ponies run.

My thoughts are, the car sat up since 2015, probably in a location that wasn’t entirely dry, like a carport. Maybe the windows were cracked open a bit, too. Oxidation formed from moisture getting in, might not have been more than fog or condensation, but it still got in, and not being driven, it didn’t dry quickly. A very good reason to regularly drive your vehicles unless you have them In climate controlled conditions.

 

[05snopro440]

That's great! I hope it works!

I have some weird gremlins in my Caprice that has sat for a while that it didn't have before. I haven't had a chance to dig in yet but you're inspiring me to do the same.

 

[26Troadster]

good you found some of the problems, hope it is the cure. the cross fire looks cool but is not a good performance setup the runners are real small, but should be good for the mrs. good luck.

 

[smallfoot]

Fingers crossed for ya!

 

[Bamamav]

We got a hawg leg now![cl[cl[cl

Finally took her down the road today, man alive! This old girl will scoot!
Pulled out of the driveway, barely mashed it, good googly moogly, it about got sideways! Looked down at the speedo, dang, I’m doing 70+ in about 1/4 mile and I’m not even holding it down! It may not have the top end with the small runner intake, but it makes up for it with bottom end torque. I can see new tires very soon!

Still got a few things to fix, heater/ ac temp lever won’t move enough to cut off the heat, so I can’t use the AC that I charged up today. Power mirrors don’t work yet, power seat is still working sometimes and sometimes not, got to get the book on the headlight system, the doors don’t close. Just some of the little stuff you expect on a used vehicle. All in all, I’m happy right now.

Thanks for the helpful suggestions!