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MG MGB Technical - Solenoid problem

I am having a problem with the solenoid on my pre-engage starter.

A few months ago the core plug above the starter came out soaking everthing in that general area. While I was waiting at the side of the road the battery drained very quickly with the hazard lights on.

I fixed the core plug but then noticed I had oil on the inside of a back wheel so the car didn't get any use. A few weeks ago I changed both back axle oil seals. Then the car would not start. The batteries were flat even though they had been on one of these clever trickle charge battery conditioners. So I desided it was new battey time.

A couple of weeks ago I fitted a single 063 battery. Went to start the car, little click from the relay, heavy clunk from the starter, but the starter did not turn. Took the starter off the car found the end bearing had dropped out on the garage floor and assumed that because the shaft was not centered the brushes were not making proper contact. So I had a quick look inside the starter to check the where no other problems. Then I refitted the bearing with a new spire clip, refitted the starter to the car. No change!

I removed the starter to the bench. Using my electrical meter I find that the high amp curcuit is not closing. The solenoid has been fitted some time in the last 10,000 miles/ 13 years and a new one is £36.

I guess water has got in and corroded the high amp contacts. Has anyone ever unsoldered the wires that come through the end cap, cleaned up the contacts and reassembled a solenoid successfully?

sorry for the long post!

David
David Witham

Hmmm, I'd have thought the starter was pretty prone to getting soaked with road water and salt anyway. Given the problem with the bearing and now apparently the solenoid I think I'd be looking at a replacement starter for reliability. Whilst the manual covers dismantling of the starter it does not go as far as dismantling the solenoid to reveal the contacts. Does it crank if you bridge the studs on the solenoid? maybe some mechanical problem in the linkage between the solenoid and the motor gear is preventing the solenoid from moving far enough to close the contacts.
Paul Hunt

Paul,

I have not tried bridging the studs. It is a good idea. As the starter is on the bench and the solenoid is off it, I will run my jump leads straight to the starter to check it turns when live.

However, with the solenoid on the bench I have checked that the pin which operates the high amp contacts goes all the way in. When it is all the way in there should be continuity from one stud to the other and there is not.

I only have a low watt soldering iron. Looking at the amount of solder on the wires that come through the solenoid's cap I guess I need to find a friend with a 100w soldering iron.

David
David Witham

David,

Yes, I regularly unsolder the wires and ease the bakelite cap off the solenoid a little at a time, remelting the solder as you go.

Once off, you can heat up the solder points ant give the cap a sharp tap on a hard surface to shake out any remaining solder - then you can reassemble easily.

Once off, unbolt the posts and clean up the contact faces before refitting.

Turn the contact bar over so clean metal faces the posts.

Reassemble and resolder the wires and all should be well for many miles more.
Chris at Octarine Services

Thanks Chris. I will give it a go.
David Witham

This thread was discussed between 21/02/2005 and 22/02/2005

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.