Real time help - starter plunger proper lube?? (1 Viewer)

[IdahoDoug]

I've got the starter apart to put new contacts and plunger in it. I'm wondering where to put grease to lube the plunger. It has a skinny section - almost a rod - with the spring around it, and the fatter section is my question. The fatter section runs in a bore and the one I'm removing is completely dry. The engineer in me says put a bit of lube on it. But the engineer in me also says it was dry so replace it dry.

What say ye??

If lube, what kind of grease? I've got everything in my shop.

On my other 80 a few years back I believe I put a light film of synthetic grease in there but I'd like to know if someone has better info. The FSM is silent.

Thanks,

DougM

 

[cruiserdan]

Doug the FSM does not indicate any lubricant on the plunger. Usually they are very specific about lubricants so I would say dry it is.

D-

 

[IdahoDoug]

Thanks - you're the man. Starter's disassembled on the bench, UPS truck should be darkening my doorstep any minute.

DougM

 

[CruisinGA]

The contacts are a wear part. Any attempt to 'lubricate' them would be counter-productive. Let them wear as designed.

I touched some white lithium grease to the plunger rod, spring and 'fat' portion.

 

[IdahoDoug]

Bruiser,

Agree with GA - those are the actual contacts and grease there would be a bad thing. I was talking about the bore the plunger slides in only. I could not resist and put a faint film on the plunger and wiped it off a bit. The spring and shaft got liberal grease as I found it.

Worked well and the starter has real life back in it. I figured the notably slower cranking (vs the 2.2kw starter in the 93) was normal. Nope - wasn't getting full juice. Whips right up now.

DougM

 

[Rich]

I expect that the contacts wear due to the sparking that happens when the contacts close and open.

 

[IdahoDoug]

Actually, it looks like physical wear to me. If they are properly installed (perfectly flat, 300lbs of pressure during attachment), then there'd be little sparking. The wear is from the heavy copper plunger pounding the contacts.

DougM

 

[Rich]

My factory original contacts that I removed are pitted and eroded. I am rather certain that it is due to the sparking that occurs when the circuit is closed and opened. Same kind of wear that occurs with breaker points based ignition, only without the benefit of a condenser to mitigate the voltage spikes.

If it were wear due to "pounding" then I would expect all the metal to be there, but deformed. What I have is metal gone, from both the contacts and the plunger.

 

[IdahoDoug]

Hmm, I think you're right, Rich. The sets I've changed had pits here and there but the plunger appeared to have slowly dented the contacts over time. But in thinking about it you may be on to something. Kind of nice that they're so easy to change. Getting the starter out is 45 minutes, but changing the contacts is only 15 minutes and then another 15 to get it back in. Reasonably field maintainable.

One of the guys on another list felt that some of the sparking was due to the solenoid (contacts and their movement) taking power from the ignition switch and not getting full power to work and move fast. He fitted a relay in the circuit so the ignition switch is powering only the relay, which then gives direct power to the starter solenoid. Seemed logical - what do you think of this? I considered doing it today, but those nice shiny contacts distracted me and I decided my job was done for another 100,000 miles.

DougM

 

[RavenTai]

The arcing is because you are breaking a large current has nothing to do with the solenoid side. Electricity happens a lot faster than you will get the plunger to move. Electricity has an inertia of sorts, when the contacts separate the electrons that were about to make the jump stack up and create a higher potential than the source voltage, there is an arc just as the contacts separate. This burns the surfaces, IIRC it burns the anode more than the cathode or vice versa cant remember witch

Sometimes you can put a capacitor and a resistor as a shunt near the contacts for this excess voltage to go to, kind of like the big gravel pits for trucks with dead brakes near passes. You would have to talk to an electrical engineer or do some research to get the right values, I do not know how well it would work in this app

 

[Rich]

I figure that when starting there is an initial spark when the plunger closes the contacts and that when the starter is switched off there is a larger spark when the plunger opens the contacts. When opening the magnetic field due to the inductance of the starter motor windings collapses, inducing a large voltage spike that jumps the gap between contacts and plunger as the plunger opens the circuit.

I assume that the ignition switch and associated starter circuit wiring is properly sized to operate the starter motor.

There are standard schemes for reducing the surges that are detrimental to contacts when switching inductive loads. I don't have any knowledge if they are ever applied to automotive starters.

Here is link to an overview of the issue: http://www.naisweb.com/e/relaye/mech_eng/mech_eng_rtia/idapm4w.html

 

[landtank]

You should not put any time of lubricant on the plunger. Doing so will only increase the possibilty of failure regardless of how little is used. I've worked on a variety of plunger stlye solenoids over the years and the only time I've had a problem is with a coil failure or a stuck plunger do to someone lubricating it. The dust can attach to lubricant and with the heat become hard and bind up the plunger. It doesn't take very much either because a little will cause the plunger to get slighty cocked in the barrel and bind up.

Just clean everything up with Isopropyl and reassemble.