MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Starter & Solenoid teardown

74.5/76/79 rubber bumber MGBs: I have looked through the archives but not found quite what I am looking for on this. I have a starter/solenoid that works about half the time. If I hit it with a stick it always works again for a start or two. I realize the problem is in this combination as I can reproduce on the bench but I still can't tell which is the culprit. Hence, I want to tear down both the solenoid and the starter so I am trying to get directions and "gotchas" ahead of time.
1) My solenoid has the two high current studs, one going directly into the starter, and then the regular and the small spade lugs. To disassemble the solenoid I see that I should remove the 2 phillips scres and then unsolder the soldered wire sticking through a rivet and gently remove the bakelite end. What I don't know is whether I should also unsolder something else. Does something need to be done with the two spade lugs? Will anything "spring apart" when I pull it apart? How tough should it be to pull out the cneter once the unsoldering has been completed?
2) When the solenoid is ready to go back into the starter, how do I connect the "pusher" to the lever in the starter?
3) On the starter, how do I disassemble this and what should I watch out for? I see the two fasteners that look like they may extend through the whole body of the unit. With the solenoid removed, do I just remove these and everything pulls out of the casing with no surprises?

Sorry to be so long winded.
Thanks
Tom Gillett

Tom

Unless you're determined to disassemble both parts I'd try to determine which part is faulty. You say you're able to recreate the fault on the bench, have you tried measuring the voltage on the terminal that goes from the solenoid to the starter during a fault condition? If there's 12V there I'd suggest the starter is a good place to start. When the starter fails to operate does the solenoid throw the pinion forward? If not the solenoid is at fault. Even if it does move the pinion forward it could still be the solenoid at fault. When it fails to work try putting 12V direct to the starter input terminal. The pinion won't move but the starter should turn. I'm not trying to stop you dismantling things unnecessary but some of the plastic parts become brittle over time and you could cause more damage than you solve.

Bob
R.A Davis

Hi Tom,

I second what Bob has said, and will add my two cents worth.

The first thing to check are the motor brushes. If these are OK, I would then suspect the high current contacts in the solenoid. After these it's anybody's guess.

The Haynes manual has good diagrams on pages 170 and 171.

Herb
Herb Adler

Thanks all,

Actually I have the solenoid and starter separated and, at this point, I am more interested in disassembling them and understanding just how they fail/work. I'm not too concerned if I have to replace both items. But, I did not perform all the good tests you have suggested when the two were connected, hence, I need hints on how to re-assemble them, in particular, how do I re-engage the solenoid rod to the starter paddle that throws out the pinion gear. I see a suspicious hole in the casting inside of which these two connect but I would like some tips from someone who has succseefully done this. Then I'll run through the tests you recommended. Also, do I just remove the two main bolts from the starter body to pull out the "guts" and examine the brushes?
Tom
Tom Gillett

Hi Tom,

To check the brushes just remove the cover band at the rear (away from the pinion gear) end and the brushes are easily accessible.
From your post I get the impression that you don't have a workshop manual. Do yourself a favour and buy a Haynes MGB manual, all the information you need is in there.

Herb
Herb Adler

Or even better a Leyland manual as well. More in that, and two sources are (usually) better than one.
PaulH Solihull

This thread was discussed between 10/03/2011 and 18/03/2011

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now