Starter Solenoid Rebuild?

[echrisconnor]

My solenoid is starting to go out. In cold weather (like now) the starter will continue to crank even after you cut power to the solenoid. Once warm, it's fine. So, it appears to me that the contacts in it are sticking. Note, it is not my ignition switch, as I have tested and bypassed it with a starter button. I'm confident that it's the solenoid.

On various Web sites, I've seen articles on people rebuilding solenoids. I'm curious whether electrical contacts sticking can be cleaned, lubed and reassembled in order to gain some more life from the solenoid. Yes, a replacement is cheap, but I always enjoy rebuilding if I can.

[Superman]

I always do too, but brazing is necessary to rebuild my solenoid and a brand new Bosch unit is about $25.

[echrisconnor]

Sup,

Were your contacts worn down to nothing, and brazing was required to build them back up? When a solenoid sticks what is sticking? Is it gummed up, or are the contacts welding together from the arcing?

Also, where are you finding a solenoid for $25?

Chris

[Gunter]

I think:
It's not the contacts sticking but, the "Bendix"-type spring pull-back could be tired and/or the O.D. of the Solenoid is gummed up and needs some cleaning and a little thin oil.

[Superman]

The brazing was needed to re-fasten a conductor that exits the body of the solenoid and attaches to a post, in my hazy recollection. I never did disassemble it. Future project for when I've got nothing better to do. Yeah, right!

I got the replacement at a run-of-the-mill electric motor shop repair place in our local industrial park. It was cheaper than the aftermarket units.

[echrisconnor]

Interesting. Maybe a cleaning is all it needs. So, is the spring which pushes the solenoid plunger out what is requried to physically disconnect the electrical connection going to the starter? The spring in mine seemed strong and it travels freely. Can binding in the starter gear retraction itslef keep the solenoid switch closed, thereby leaving the car cranking away?

[Gunter]

The other way around: The internal spring holds the starter back.
Electromagnetic force in the Solenoid winding moves the starter forward into the ring gear on the flywheel, at the same time the contacts close to make the starter motor rotate. When current to the Solenoid is discontinued, the internal spring pulls the starter back.
The Solenoid plunger may just need cleaning and some light oil.
Take the starter off and test it on a bench.
Do a search on this board on how to do it.

[echrisconnor]

Gunter,

I think we just got our terms crossed. I was referring to the spring pushing the solenoid plunger out, which is what retracts the starter gear. I've had my starter fully apart, but just haven't dug into the guts of the solenoid. It has to be gooked up on the inside though, since when I had it out, it was clean and i cleaned up the external shaft of the plunger.

Your diagram is excellent though. It shows clearly how the contacts are made in the solenoid. It also shows how if the drive gear remains stuck out, and does not retract mechanically, then the contacts could be forced to remain closed in the solenoid...

Chris

[unclebilly]

Go to your local auto parts store, you can buy an aftermarket one (I think beetles used the same solenoid) and it's a simple install. Make sure you clean and grease your bendix with high temp grease.

[Early_S_Man]

Not really a mechanical failure ... corrosion buildup on solenoid plunger, AND clutch disk wear particles collecting on everything -- the bendix mechanism, shift lever pivot, solenoid plunger, etc.

A thorough cleaning and lubing with Valvoline SynPower Synthetic Grease with moly #985 or #986 ... takes care of the intermittent failures, for a couple of years, anyway!

[unclebilly]

If the grease is not high temp, it wall gum up and cause it not to engage... I had to take mine back apart a week after I rebuilt it and put in high temp grease - it's been fine ever since.

[vannesing]

What a great idea

[911pcars]

Originally Posted by echrisconnor

Gunter,

I think we just got our terms crossed. I was referring to the spring pushing the solenoid plunger out, which is what retracts the starter gear. I've had my starter fully apart, but just haven't dug into the guts of the solenoid. It has to be gooked up on the inside though, since when I had it out, it was clean and i cleaned up the external shaft of the plunger.

Your diagram is excellent though. It shows clearly how the contacts are made in the solenoid. It also shows how if the drive gear remains stuck out, and does not retract mechanically, then the contacts could be forced to remain closed in the solenoid...

Chris

Correction: The spring in the solenoid housing doesn't push the pinion gear into mesh with the flywheel. When energized, the solenoid plunger travels to the left (see diagram) which causes the linkage to move the pinion gear to the right into mesh with the flywheel ring gear. When de-energized, the return spring forces the plunger and the pinion gear (via the linkage) back into their at-rest position.

A good idea is to remove the starter, then bench-test it with some jumper cables and a charged battery while observing the action of the pinion gear. It's not a friendly environment inside the starter. Lube can dry out and allow metal-to-metal contact which increases friction.

Sherwood

[T77911S]

its not hard to "rebuild" the solenoid. i have been planing on doing one and posting a how to, but building my garage has taken prioity.

whats cool about this is you basically have spare parts in the solenoid.
only about half the contact on the 2 studs makes contact with the plunger. so you can pull the 2 studs out, clean them, then rotate them 180 degrees and have new "meat". same thing with the contact on the plunger, clean it, then rotate it 180 degrees.

the only real hard part is the soldering. take a wire brush and clean the solder joints real good. i use a standard soldering iron to heat it up. a little tip- put a little solder on the tip or between the iron and the solenoid. the liquid solder helps to transfer heat and melt the joint easier. i also have a solder sucker which helps too.

but a wire can be used too. strip off a few inches of insulation. when the solder on the solenoid melts, put the wire in with the solder and the iron. once the wire heats up enough, the solder should start to flow into the wire. the trick here is too keep the solder liquid, but transfer the iron to the wire, and slide the wire through the solder. the idea is the solder will flow to the heat in the wire. i have not tried this on a solenoid, but it may be tough since it is such a large device and that makes it hard to keep the solder liquid.
some wires take solder better than others, so you may need to have a few around to try.

another way is to heat the solder, get it good and hot, then quickly bang the solenoid on your workbench knocking the liquid solder off. it works, but protect your eyes please.