Difficult issue to diagnose

[ranger372]

This potential serious issue will be hard to describe, here go's.

On a long 400 mile trip, I was on the interstate running 65 mph (3200 rpm), Cylinder head temp about 375 deg. About 150 miles in, I felt what I thought was a cylinder miss. I looked at the Tach and it was fluctuating back and forth about 500 RPM's. off of 3000

I pulled onto a off ramp and pulled into a empty lot. Shut the engine OFF immediately. I heard something still running in the engine bay. Got out and opened the hood................THE STARTER WAS RUNNING, the fan was not turning, so I would say the Bendix was not engaging (That was a good thing). Also I would like to point out the key was in my hand. I immediately went to disconnect the quick disconnect negative battery terminal and the green knob was melted and just turned like chewing gum. Frantically I searched for a wrench in my tool box. Disconnected the neg. cable and all stopped.

I walked to a service garage for advice----Got Nothing. I got back to the car about a half hour later and decided to just touch the Neg cable to the battery and the STARTER ENGAGED, keep in mind the ignition switch was in the OFF position and the key was in my pocket.

Now, I've decided to disconnect the two smaller wires at the solenoid. and push start the car. While Beginning to jack the car up to access underneath the car, a car/guy pulled into the lot to offer assistance. I explained the issue and when I showed him how the starter reacted when the neg cable was touched to the battery............THIS TIME NOTHING (key was still in my pocket), about an hour had passed and the engine had cooled down. I put the key into the ignition and the car started immediately as if nothing had ever happened. I continued on my trip about another 75 miles to our Hotel for the night. made a few stops that evening and the car shut off/started several times.

The next morning I continued to my destination another 150-200 miles without incident, shut off/started several times. After the initial incident, I kept the car at 60-63 MPH and the RPM's at 3000, Cylinder Temps at 360 degrees or less. We ran the car at our destination at our destination for four days. When going home (400 Miles) we drove the on the interstate most of the way at the 60-63 MPH again without incident.

Anyone, Please, What happened? Heat? What to look for? What to replace? Starter was rebuilt about 1400 miles ago. I am truly puzzled.

Car is a '65 Corsa w/Turbo

Thanks,
Steve D.

[joelsplace]

The starter has issues if it was running but not turning the engine. The starter motor should be able to run until the starter gear engages the ring gear.
The heater hose that runs over the starter can cause shorts to ground but I can't see how it would make the starter run.
The starter running continuously could melt the cable if there was a bad connection.

[bbodie52]

For the starter to crank the engine, the solenoid must physically move the starter drive gear to engage with the engine ring gear. When this movement takes place, a large contact disc inside the solenoid makes contact between the thick positive cable battery terminal and the electric motor terminal, to apply voltage to the motor to rotate the engine.

The solenoid is normally only energized to move the drive gear to engage with the engine ring gear when voltage is applied from the ignition switch in the START position, which applies voltage from the ignition switch to the solenoid "S" terminal via a purple wire that connects the ignition switch to the solenoid. This is the normal operation of the starter system.

The only way that the starter motor itself could be energized without the Bendix gear drive having physically moved into position to engage the drive gear with the clutch ring gear would be for the large disc that connects the battery cable terminal to the motor contact to have stuck, or "welded" itself to the two high-current contacts inside the solenoid. A short between those two large contacts would continuously apply battery voltage to the motor WITHOUT THE DRIVE GEAR IN CONTACT WITH THE CLUTCH RING GEAR. Since the starter motor is a high electrical current device that pulls more current than anything else in the car, continuous operation due to a stuck switch inside the solenoid would likely overheat the thick battery cable and associated battery connector (causing it to melt, as you described). The stuck internal switch contact disc in the solenoid may have ultimatly broken free of the contacts, permitting normal solenoid operation to resume.

The continuous high current draw by the motor may have over-heated the motor, but if you were lucky the motor may not have been permanently damaged. I would suggest removing the starter and inspecting the Bendix gear drive and associated return spring for good condition and free movement. The internal motor switch disc inside the solenoid (on the left side of the illustration below) may have been burned or damaged, and you already know the positive battery cable terminal was overheated and damaged. I would replace the solenoid with a new solenoid, and replace the positive end terminal or the complete cable to restore full service condition to the solenoid and cable. Hopefully this will eliminate the damaged components from your car and the cause of this unusual failure will be eliminated.

BASIC STARTER PRINCIPLES AND FUNCTIONS
viewtopic.php?f=225&t=13423&p=92687&hil ... oid#p92687

[ranger372]

Understand what Brad said in his response above and I am in agreement as to the solenoid being the likely problem, Thank You. My thinking however is that it was the negative cable/terminal that had built up heat and melted the green knob on the terminal quick disconnect. Would it not be the Positive cable that would be damaged due to the starter motor continuously running? Positive cable is fine, I can not say if the positive cable was hot at the time of the incident. Further thoughts?

Steve D.

[joelsplace]

Both cables have to carry the same current. The one with a bad connection (high resistance) is the one that will melt.

[bbodie52]

I misread your initial post and thought you first tried to disconnect the POSITIVE cable, and thought that the positive connector was the melted connector. I then assumed you used a tool to disconnect the negative cable connector to halt the starter motor. In any case, my suggestion was to remove and replace the damaged (overheated) connector or connector and cable, in addition to the likely faulty starter solenoid that kept the motor energized in the first place.

There is no way to know how long your starter motor was energized and running while you were driving. The noise of the motor continuously running was likely masked by the engine sound. Since it was running free and not engaged with the clutch ring gear, it could have been running since the last time you started your engine (perhaps more than an hour). Since it was not doing any hard work, like cranking an engine, the heat buildup in the starter and starter circuit was likely somewhat gradual. But it is still a high-current circuit that is only intended to run for a short period of time, so continuous high current flow would certainly heat the motor and connecting cables. As mentioned in the previous post, heat buildup is increased wherever the electrical resistance is the greatest. If your negative battery terminal was somewhat dirty or loose, it may have been the point of greatest resistance to current flow, so may have generated more heat than other portions of the circuit. The physical damage you discovered on the plastic portion of the negative connector is the evidence of high heat buildup, and the continuous heating and deterioration of the negative battery connection may have eventually introduced a noticeable fault in the ignition system operation as available power deteriorated to the point where the ignition system began to misfire. (If this had occurred at night, your dimming headlights might have been your first warning sign).

...I felt what I thought was a cylinder miss. I looked at the Tach and it was fluctuating back and forth about 500 RPM's. off of 3000...

[66vairguy]

Both cables have to carry the same current. The one with a bad connection (high resistance) is the one that will melt.

CORRECT!! The "GREEN" disconnect switch has a higher resistance at the knob connection, but normally works fine. The switch will get hotter vs. a regular (and clean) battery clamp under high amperage demands (starter running), but the starter run time is normally brief and it's not an issue.

Anyway ----- Depending on your need for reliability, you can run it until another starter problem happens, or replace the starter and solenoid.

I'd replace the solenoid AND starter. If something was shorting at the solenoid terminals (I've seen this) the solenoid would engage the engine. If ONLY the starter runs it was probably a short INSIDE the solenoid (not common, but happens). Starters will only run without damage under load for about a 15 seconds. Without a load they use less amperage (still considerable) and exceed the normal operating speed which is hard on the starter motor bushings and brushes.

[erco]

Wow, that's a scary story. In addition to the great advice above, I would add to check the ignition switch and all the wiring between it and the starter solenoid. And even if the starter survived, I would remove it to check the bushing & brush condition.

Related, I have new bushings and a NOS end bell for a Corvair starter that I bought but didn't need for my starter rebuild. For sale at my cost if anyone wants, PM me. https://www.walmart.com/ip/New-60-66-Ge ... /542721660

Google maps caught me rebuilding my starter in my driveway last year.

[ranger372]

Decided to replace the Solenoid - ordered from Clark's (wanted the Delco). The starter rebuilder most likely used a cheap Chinese solenoid. Clark's delivery will not be here till next week.

Thanks again,
Steve D.

Today I was notified by Clark's that the solinoid was 'out of stock' both the Delco and the no name. Tomorrow I will go to NAPA

[erco]

Yes, someone here warned me about cheap modern solenoids using less copper and weaker return springs. Check for wear on your starter drive, too.

Newer cars that shut off and restart at stoplights must use beefed-up starters, that's a lot of wear & tear. Of course I marvel at their ability to reliably and instantly restart on the fly first time, every time. No carb flooding, gas pedal pumping, choke unloader, etc. Nice!

[ranger372]

I Thank everyone for their comments. I am almost too embarrassed to say what the problem was.... Once I got the car into the air and me underneath the problem was obvious. The 6ga red wire was EVER SO close to the purple wire at the Starter solenoid. There was a bit of burnt/weld residue on the terminals. I've separated the two and there appears NOT to be any damage to the starter or solenoid, ALL IS GOOD Again Thanks!!!