Not good with Electric...

[BusaDave9]

correct me if i am way off but this ground block is supposed to be a junction for the wires and NOT the actual ground......meaning that there should be another battery cable coming from there going down and attaching to the frame or the engine block?

steveno will be double checking the wiring but yes it appears that left terminal block is ground, directly connected to the battery. Normally there is a smaller ground wire from the battery connected to the firewall here. But the way the PO installed this terminal block it is isolated from the firewall. That's wrong. The ground wire from the battery should be connected directly to the firewall.

So the cable on the right is connected to 12 volts on the battery. It shorted to the firewall via the bolt. The firewall wasn't grounded properly so the firewall and blower motor were energized with 12 volts. The ground wire on the blower was connected to ground and it drew all the current back to the battery. The battery drained and the engine failed to start.

There should also be another ground wire from the battery to the engine block.

 

[steveno]

The wire you have circled is the positive wire from the front of the battery terminal. So you think it touched that bolt and energized the firewall and the wires on that ground block on the left took in the juice off the firewall? Hope it didn't go to other places. At least I'm starting to get an idea of the electric with your guys help. I can pretty much do anything else but electric is like a big curve ball with all the fuses and relays and stuff. Can't wait to get home to work on this.

 

[cerrajero]

this is turning out to be very educational........
I was told WAY back that the best way to find bad grounding and bad connections is with the engine running ( or all components energized )

test battery...... it says 13.8 then take off negative tester and attach to block or an grounds you can reach.....it should be within .4 to .5 of the original 13.8
and its the same with all your grounds......if not on one of the grounds then you can narrow it down to that particular part

and if not running it should be within .4 to .5 of the original battery read

that what i was told the better way to test bad circuitry
which maybe the backwoods shade tree georgia mechanic way and totally wrong

 

[steveno]

I like the backwoods way, seems much easier and makes sense to me...
Thanks.

 

[TroyaCantrell]

Steve, your real problem is what Dave pointed out, you have got to fix that ASAP. Your luck that all you did was burn out a wire to the blower motor. When that 12volt + hits or gets close enough to that bolt you are putting 12v + back through every device that is grounded, meaning all of them.

Your lucky that all that happened is a burnt wire and not an exploded battery. I have seen that happen and it is not pretty.

If you are going to keep it get some rubber hose and get it around the shank of that terminal on the wire that leads back to the positive side.

The - or ground side is fine. It is both the junction and the actual ground, or one of the actual grounds you could still have one to the block.


Troy Cantrell
Sent from my iPhone using Tapatalk
Build thread - '66 CJ6 :
http://www.jeep-cj.com/forums/showthread.php?t=15075

 

[cerrajero]

no disagreements on that
but if the grounding block is the left one and the wire that he is holding (which looks burnt) is the blower ( as well as leading to the ground block)....


totally agree with Busa about the short with the bolt but why the ground part of the blower burning intead of the positive? if there is no bad grounding
and thats a question for my education as well

 

[BusaDave9]

I would recommend putting a ground wire from the block on the left to the firewall. The factory puts a ground wire on the firewall. If those ground wires on the block on the left were all connected to the firewall itself the blower wire never would have burnt. When the 12 volt cable on the right shorted to the firewall it would have returned via the ground wire that should have been on the firewall.


When that bolt touched the 12 volt cable the firewall had 12 volts. Anything bolted to the firewall (such as the blower motor) would then have 12 volts. The makers of the blower motor expected the firewall to be grounded. They also added a ground wire. So when the blower motor had 12 volts all the current went through that small wire and burnt it up.

 

[BusaDave9]

why the ground part of the blower burning intead of the positive? if there is no bad grounding
and thats a question for my education as well

The positive wire is a big cable that can handle high current. That same current also tried to go through the small wire. That's why it burnt up.

A bad ground causes too little current to flow. But it flows where it should. If you have head lights with a poor ground the lights look dim. (or maybe won't come on)

A short causes too much current to flow but it flows where it shouldn't (such as the firewall and that small blower wire) The short then drains the battery and the starter won't run.

 

[BusaDave9]

Another thing to remember is, for any circuit, the same amount of current flows through the entire circuit.
For example a headlight: If the headlight has 10 amps of current flowing through it then there is 10 amps leaving the battery. 10 amps through the switch. The wire to the headlights must handle 10 amps and of course the headlight itself has 10 amp flow.

This also holds true for a short circuit. We might have had 70 amps flowing through the big battery cable to the terminal block on the right. 70 amps through the firewall to the blower motor. And 70 amps through the tiny wire back to the grounding block on the left. It's the tiny wire that couldn't handle it.

To make a comparison. If you connected a tiny straw to a fire hose both would need to handle the same current. You wouldn't have to worry about the fire hose but the straw would burst in a second.

 

[steveno]

Ok, got home from work and opened a beer...... going to work on it today. Put the battery on the charger was at 8 volts, so it did start to drain the battery. Taking more pics now, so it's very possible that everything on the left ground block could have fried, and or everything connected to the firewall. One good thing is the PO put in alot of relays and fuses. Pulling the alarm now.

 

[steveno]

Busa, yes that is a junction box for the wires, the right side box. I ran a jumper from positive battery termial to starter wire side of starter solenoid and it tried to start the motor. I charged the battery. I accidentally tried it in 1st gear and it rolled the jeep a little, then tried in nuetral and it tried to turn the motor. I also pulled the fuse for the heater blower.
Can I ground the blower motor somewere else besides that ground junction block so it doesn't contact the other grounds or it doesn't matter? I put a volt meter on the positive battery termail and the starter solenoid battery side, thought I would get a reading from a full battery but no reading at all. Is it possible the positive battery cable is bad?

 

[steveno]

Yes there is a ground going to the engine block from battery. I removed the alarm also. I will put a wire from the ground junction block on left to the firewall now.

 

[steveno]

Ok a friend who is a backyard mech. stopped by and got the jeep to crank and replaced a ground wire to engine block from battery. Still no spark or gas. He told me to pull the ignition module and get it checked. I did autozone said they can.t check it so bought one for 40.00 bucks installed and same thing. My friend is going to call later to see how it went. In the meantime i figured if it's cranking and no spark or gas something isn't getting the signal. All fuses are good and relays look good. I took the ECM out and ran it to pep boys to see if they can test it. They don't. A new one would be 50.00 which doesn't seem bad. But on the computer at pep boys it said it needs to be programmed off the old one. I thought well if the old one is bad how the hell can they do that. And the guy at pep boys was clueless. Can't get ahold of my friend right now. So I took the ecm apart just to visually check it, simple enough. The pic below shows a break in one of the silver lines. I'm thinking that is a problem. Should I get a new one? I do have an adl cable and odb program downloaded on my computer, could',t I program it myself if I get it running?

 

[steveno]

Could I have a computer repair store fix that real quick?

 

[BusaDave9]

Can I ground the blower motor somewere else besides that ground junction block so it doesn't contact the other grounds or it doesn't matter?

No that doesn't matter but I would put a ground wire from the left terminal block to the firewall. About 12 to 8 gauge wire. If the firewall was grounded that would have protected your blower and other components.

I put a volt meter on the positive battery termail and the starter solenoid battery side, thought I would get a reading from a full battery but no reading at all. Is it possible the positive battery cable is bad?

That's normal. There should always be 0 volts across both ends of a wire or cable. You would have to go from the positive side of the battery to ground to read 12 volts.

^ ^ ^ now there's a problem. You blew the trace off that board. You need a new ignition control module.

 

[steveno]

I'll pick and new ecm tomorrow. Does anyone know about the programming part of it? I will also ground that block to the firewall before I put the new ecm in. I do have the hook up for the computer in the Jeep but I think it has to be running for that to work. I usually work on the jeep in new jersey where all my tools and room to work is. It sucks here in the city working on the street with Limited tools. Anyway I'll post progress tomorrow.

 

[steveno]

Busa, when you say I need a new Ignition Control Module. Do you mean a new ECM? I put a new ignition control module on today. That is a pic of the ECM above.

 

[BusaDave9]

Oh yes, sorry, the ECM Pep Boys have is generic and needs to be programed. To get one pre-programed you will pay more.
check out this link: RockAuto Parts Catalog[ID]=0&ck[idlist]=0&ck[viewcurrency]=USD&ck[PHP_SESSION_ID]=gh4qhadqatd90c563fql6lhma1

I use Rock Auto often.

 

[steveno]

Will call the PO on what to get. The ECM is from an 89 chevy 1500 pickup 4.3L. The rest of the TBI I believe is from a 92 Chevy 1500 pickup. I have to find what I need the TBI programmed for. And I have a 79 AMC 258 i6 / 4.2l AMC 258 i6 / 4.2l in the 84 CJ7 . It has a spark control and OBD (I think that is what it is called) connection for the laptop to tweek it. Maybe I will just call Rock Auto tomorrow and they would know, thanks for their website.

 

[steveno]

Couple of pics.