engine and drivetrain Melted wires in engine room

[Juel72]

I am in the proces of refurbishing the engine room in my 1975 2002.

Engine out and all.

Yesterday I discovered a couple of burnt wires. See the pictures.

It is in the loom that goes to the starter and alternator. And also the ground wires below the brake fluid reservoir.

what happened?

Any good ideas

B/R

Flemming Juel[/i]

[Hans]

First guess is you didn't deal with ground strap to block. Poor connection or not there at all.

[Hans]

And the alternator should have a ground wire to head

[AceAndrew]

I concur with Hans,

Your engine was trying to ground through the alternator wire, which in turn overheated and started to melt the other wires. Even if you have ground wires in place from head to alternator and block to frame, replace them.

Be thankful it wasn't worse.

[Mike Self]

Check the negative ground strap--the proper factory one has two flat, braided leads. The thick one goes to a bracket bolted to the block that also supports the rear of the starter motor. A thinnner one is bolted to the body, just to the right of the battery box. Without that body ground strap, when you engage the starter, the ground path runs through the accelerator linkage--not a good idea! Aftermarket ground wires don't have this dual strap.

And since the alternator is mounted in rubber bushings (better replaced with urethane) there must be a heavy (12 or even 10 gauge) wire running from the alternator frame to the engine block.

cheers

mike

[Napes]

As a clarification, according to the factory Repair Manual (11 ─ 14/1), the ground wire from the alternator goes under the bottom, inboard bolt of the upper timing cover, not the block per se. Accomplishes the same thing - just easier to connect as per the factory instruction.

Bob Napier

[jimk]

And on the passengers side, there should be a ground strap from a bolt on the rear of the head to the fender.

[Hans]

Jimk - I've never seen that one. Are you sure it wasn't a kluge to attach ground strap without clearing access to normal spots on driver's side?

[Napes]

Jim; I just emailed you with the same question as Hans.

Bob Napier

[eastsidebimmer]

And on the passengers side, there should be a ground strap from a bolt on the rear of the head to the fender.

I think this is EuroSpec only?

[Preyupy]

The big Battery + wire to the starter needs a equal size Battery - wire, the starter pulls over 100amps. If the engine ground strap is missing or has a bad contact at the block or chassis it is going to try and run all the curent through anything it can find. 18 gauge wire for the charging or ignition systems, throttle linkage, choke cable etc. Check the ground strap first and make sure it's big enough!

[Juel72]

Thanks for all your replies,

The factory mounted ground strap has always been there. It's old but not damaged. the connections may have been bad.

The alernator to head ground wire is also OK.

There's a possibility that it could be an old problem. The insulation was burned a non visible place. I have not faced any electrical problems before.

But I will renew the ground strap when installing the engine.

How much of the wiring harness should I replace?

B/R

Flemming

[Hans]

I'd be checking the cable mounting points - make sure the flex cable ends are clean and down to bare metal - use wire brush or emery paper. If block is painted, make sure threads are clean, likewise the bolt. There needs to be a good connection for that amperage.

[AceAndrew]

Thanks for all your replies,

The factory mounted ground strap has always been there. It's old but not damaged. the connections may have been bad.

The alernator to head ground wire is also OK.

There's a possibility that it could be an old problem. The insulation was burned a non visible place. I have not faced any electrical problems before.

But I will renew the ground strap when installing the engine.

How much of the wiring harness should I replace?

B/R

Flemming

This isn't something that comes and goes intermittently. I'm guessing your starter has been taking progressively longer to turn the engine over?

When you say the Alternator to head ground is OK, what does that entail? Did you use a voltmeter and check resistance? Mine looked "ok" as well, but was old, brittle, and largely non-conductive.

Replace the fried or overly-stiff wires (remove insulation to visually check and use the Voltmeter). Most likely these will be the wires between the alternator and regulator, but check any other lines that may be collateral damage (basically from the driver's side of the radiator over to the regulator).

[Hans]

On the harness front, I would slice open the loom and see what has cooked. You may get away with replacing a few wires. You should get the wiring diagram to see where those wires go.