Starter? electrical problem, help (1 Viewer)

[nspctr1]

OK, On my 75 FJ40, 2f, stock, new battery, not my DD and hasnt been started in a few weeks. I went to start it this pm and it cranked over, ran for a few minutes then melted the hot wire that comes off the positive battery terminal into the harness on the passenger side. I went through everything w/o the wire hooked up and it all works fine. Once you hook up the 10 ga. wire from the battery terminal it starts smoking. I asked a buddy of mine and he says when a starter sits for a while it can get a flat spot in it which would cause slow cranking and after a while it could possibly freeze the brushes or something could break off and cause this problem. Does this sound right? Any ideas?
Thanks

 

[Steve C]

The heavy juice through the starter goes through the biger of the two wires off the + side of the battery.

Question 1, when the wire is smoking, is it with the engine on or off?
Question 2, did the amp meter peg one way or the other during this event?


Assuming that it is melting with the engine off, I would get out the ohm meter and start looking for a short.

Assuming it is smoking only with the engine on and in the charge direction on the amp meter, I would look at the voltage regulator.

You need to be very careful with this though, as it could cause a fire.

All just my personal opinions.

 

[nspctr1]

It does it when you turn the key on. I can jump the terminals on the starter and get it to turn w/o the wire connected which also leads me to solenoid/starter. It's the smaller of the wires from the positive bat terminal. anyone know what this feeds?

 

[Steve C]

Did you notice which way the current meter went on the dash? (charge or discharge?)

When you say it's when you turn the key on, do you mean to the "run" position or fully to the "start" position?

That wire goes to the amp meter, then to the alternator, then the key switch, then the starter and power distribution.

What you are looking for is either the voltage regulator is toasted, allowing full juice back to the battery, or a short somewhere.

Check out the wiring diagram on the links section.

 

[nspctr1]

Thanks, I didnt pay much attn to the amp meter when it was toasting, I was trying to keep it from frying further. I can hook it back up I guess and see what it does, It does it when I turn the key in the run position. dont even have to try and crank it. Is there no way it can be the starter? I took if off and when I removed the wire on the right hand side, little one probably 14 or 16 ga. the screw fell into the solenoid/ starter. All connections are pretty rusty. Also, this rig would start and run fine until I pulled the two coil wires off and cleaned them up and the starter wire and cleaned all terminals. It was turning over slowly and thought the connections were bad. I started it this pm after that and got smoked!!!

 

[65swb45]

As a preventative measure, you should buy and install some fusible link wire between the wire on the battery that is melting and the battery itself. The wire in question is bundled into the center of your main cowl loom, and if it melts, it WILL TAKE OUT YOUR WHOLE WIRING HARNESS! YOU WILL BE FAWKED! Fusible link is designed to melt before anything else.

The other suggestions posted here are all very good and useful. Ask lots of questions and be very careful.

Mark

 

[Steve C]

The small wire off the battery dosn't hook to the starter until you turn the key to the "start" position.

Fusable link-- excellent sugestion (should be there anyway). You may want to get a 20 amp circuit breaker from the boat store for test purposes.

It sounds like there is a short it the wiring. Typically, what you want to do is leave the battery off and trace the wires with a Volt meter (using the Ohm, or resistance feature), removing and inspecting wires until the short is located.

If your not familiar with electrical devices and wiring diagrams, this may be the time to call in a pro, as an electrical fire is an easy way to set the car on fire.

 

[Romer]

I think its a bad ground. Take the ground wire from the battery and follow it to the frame. Remove it from the frame and clean to bare metal on both the frame and lug and tighten down. Also should be a battery type wire (Thick) from lig on starter to frame or ground spot. Make sure there is good metal to metal there.

Ken

 

[Pin_Head]

It sounds like you have a short somewhere between the key on position (or accessory position if that is the one where it starts smoking) and the fuse block. Download a schematic from the tech links section and check it out. The good news is that it is only 1 wire or circuit and it is pretty short.

BTW, if you had a fusible link in this wire at the battery it wouldn't burn up.

 

[Steve C]

Pin_Head is right on target.

Bad ground won't cause over current condition in the + wire out of the battery. As the resisitance goes up the current goes down.

 

[Romer]

He said the wire that goes into the main harness, not the main battery wire. This would be a smaller gauge wire. A bad ground from the battery to the frame would in fact raise the voltage potential from the Hot wire to the return back to the frame. It depends on what this harness wire is feeding on if that would cause a problem. The main battery wire (Thick) would not have this problem. I'm not saying that the potential on the wire itself would make it hot, but what its connected to might have a problem drawing extra current.

I had a poor ground, hot wires and the point were the battery (-) wire connected to the frame would glow if the starter was on for a few seconds. Cleaned up the ground and that and my headlight problem went away.

You guys are probably right that its something else, but it's always good to make sure you have a good ground, because ground loops can give you funny readings when you are troubleshooting through the harness.

I would never disagree with Pin-head, he guessed it was only my rod bearings when I siezed my engine.

 

[nspctr1]

Was told by the dealer today that one of the brushes could have broken in the starter and grounded out against the case. Is there a way to test for that or just crack the case and look inside? As mentioned earlier, this rig is not a D D and has been under resto work for the past 3 years although started almost every other month. The starter drug the last time I went to crank it so I pulled off the Positive cable on the starter and cleaned it up, very rusty, and the 2 coil wires and cleaned them also, climbed in the cab and cranked it over and after a few seconds I had smoked the wire attached to the positive cable. I am going to get a fusible link for this connection, 20 amp seems to be the best? but, what would you check first, starters are about 100 bux locally and cant dump money into it since I have recently been laid off and was being forced to sell the rig anyways, I just want to make sure if I do sell it that who ever buys it is happy and doesnt get a POS. thanks everyone for your help!!!!

 

[nspctr1]

OK, took the bait, bought a new starter and still burning wires !! any other suggestions. thanks

 

[Pin_Head]

I would never disagree with Pin-head, he guessed it was only my rod bearings when I siezed my engine.

A bad ground acts like a resistor, so it won't raise the voltage, it will only pass less current.

From what you described, you can tell that it is a short somewhere between the key and the fuse block. Best place to look first would be the fuse block, since it is accessible and then the ignition switch, since it is subject to wear.

It ain't anything else and it is nothing less (unless you got the description wrong).

 

[nspctr1]

I was looking through the fuse block, all fuses are good, cant see any burned or deformed wires, seems to be OK, how else would you test it. I hooked the wire up to allow current to flow through and it pretty much reads normal. I must be brain dead because I just cant figure this damned thing out.

 

[Romer]

A bad ground acts like a resistor, so it won't raise the voltage, it will only pass less current.

Allright pinhead, I am a lousy Electronics Engineer I knew that. Must be that I am management now.

 

[Pin_Head]

Allright pinhead, I am a lousy Electronics Engineer I knew that. Must be that I am management now.

Are you an EE? I was just funnin wichyou. If the ground is loose, it will arc and get REAL hot locally, but not the whole wire.




For finding the short:

It starts smoking only when the key is on, right? Which switch position? If not you have a different problem.

(Edit: You don't have to wait until it smokes, it should peg the amp meter in the dash.)

If it smokes in the Accessory position, then check the light blue wire with a red stripe that goes to the fuse block. If it only smokes in the Run position, check the Black wire with a yellow stripe. If it only smokes in the Start position, check the Black wire with a white stripe. this last wire doesn't go the fuse block; it goes directly to the starter solenoid. By check, I mean disconnect the wire and see if the problem goes away. If so, then the problem is after the wire you disconnected, like the fuse block or solenoid is shorted. You replaced the solenoid too? If so, it is not likely the problem. Try removing the fuse block from the fire wall make sure that the contacts inside the box are not touching ground. The problem is not after the fuse or the fuse would blow.


If it doesn't go away, you have to follow this wire back to its next connection at the ignition switch. Check that the insulation is intact and not shorted to ground. This means taking apart the steering clumn and getting into the switch. Disconnect the wires at the switch and see if the problem goes away. If so, the switch is shorted and needs to be replaced.

If the wire gets really hot, it would be better to diagnose it with an ohm meter. You can disconnect the wire at the battery + lug and alternator B lug and pull all the fuses out. Check the resistance on battery wire to the ground. If it is zero with the key on, it is shorted. Then start pulling the wires described above and look for where the resistance goes up to infinity. the short is after the wire that you disconnect.

One more hint: the wire going from the switch to the solenoid is a much smaller wire. If this circuit was the problem, then this small wire would smoke and not the big one. chances are, it is not a short in a small wire.

Disclaimer: the wiring diagram I have is for an '81 and I don't know that the color code is the same, but it is for my '76. The diagnosis depends on your description of the problem so the more you can tell us the better.

Good luck. electrical shorts are a biatch.

 

[65swb45]

Now that PinHead mentions it, I seem to recall a couple of ammeter-caused cases like yours that were started by the water that comes in thru the windshield gasket and hits that side of the instrument cluster. You should pull the cluster [with the battery disconnected] and do a physical inspection of the ammeter leads and wires. Pitting on the retainer nuts is a sure sign of the moisture I am talking about.

And, like PinHead said, wiring is a biatch.

 

[nspctr1]

Thanks pin_head for your info and expertise, I apologize If I am repeating myself but, The wire only smokes when I turn the key in the accessory position, I have a electric fuel pump that usually starts running when I turn the key on and it isnt running either. Could it be that? It is hooked up to the hot side of the coil? I will check the wires mentioned by pin head and try to locate the problem that way also. Thanks for all of the help !!

 

[Steve C]

here's a brainstorm, how about unhooking the wires from the coil and starter and seeing if it goes away. (that's when it started, wasn't it).