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MG MGB Technical - '77B key spun in ignition

Hey everybody -
I checked the ignition switch archives, but did not find exactly my problem.
I recently was going to drive my '77B to the body shop for a little beautification project. Inserted the key, turned it and something "snapped". The key would now spin freely in the switch, but nothing would happen. The car was in the "on" position - so dash lights were on, fuel pump was clicking, but starter had not fired. Could not turn it off either, it would freely spin either way. I disconnected the fuel pump until I could get my Haynes manual, check the wiring diagram, and rig a connection to the starter wire so that I could get it running, and get it to the shop.
I thought I had a bad switch, and ordered a new one. Interestingly, when I took the black plastic pieces off the steering column and took out the switch, it worked fine (actuating it with a screwdriver). So the problem is in the key/tumbler deal somewhere. This part I don't understand very well. I was wondering if from this description, anyone could tell me if I have to order a whole new steering lock set-up, or if the "lock barrel" alone is the problem, obviously that would be alot cheaper to replace.

Thanks. Jeff
(now in Connecticut - same email.)
Jeffrey Delaney

Jeff,
Hope you're enjoying the cold weather in Connecticut. ;) I don't know as though just the tumbler assembly is available for a 77B ignition. Another question worth asking: How does the key look? If it's the original ignition, it's now 26 years old, and the key is probably pretty worn out. When I tried to get a key made for my 77b, no one could do it because it was so worn out. I bit the bullet and put on a new ignition assembly. I'm glad I did too. No more worn out keys, no more worn out wires, no more problems with the ignition system.

No problems are good problems, =)

Justin
Justin

Justin -

Thanks for the reply. I don't know if the key I got with the car when I bought it 4 years ago was original. However, it was the only key to the car - so I had duplicates made. They all worked fine, so I did not worry about it. I don't think that the key was worn, so as not to catch in the tumber, I think it is that mechanism. The moss catalogue shows a "lock barrel" that you can order separate from the whole apparatus. It appears to come with keys so I was hoping that this was the only thing I would need to replace and I could forgo drilling into the sheer bolts and taking that whole thing apart and replacing it. Also - it is about $100 cheaper.
Thanks for any additional thoughts on this.

Jeff
Jeffrey Delaney

Several years ago I had problems with the column lock on my 78B. I went at it a little gingerly, but I was pleasantly surprised that I was able to disassemble it without problems from the shear bolts (maybe they had been replaced with standard bolts at some point in the past?).

The lock mechanism has a lot of pot-metal parts, and so there is a fair bit of wear over time. On mine, when I took it apart, I was able to tweak and twiddle it all back into good working order when I had the pieces on the table in front of me; didn't have to buy any parts. My problem was a little different though, it wouldn't unlock the steering column.

I would suggest giving a try at removing the whole lock mechanism before buying parts; it will give you a much better picture of the problem.
Tom G

The inexpensive cylinder you wish to use as a replacement is for an older model with no locking steering column, if I understand the catalog.

As stated, the later models had all pot metal parts. Probably what happened is the blade which actuates the plastic switch on the back of the lock mechanism is not in contact with the key cylinder due a broken part. These are ticklish to repair and would require a new lock cylinder.
jim mindy

As a general note. The threads of the shear bolts are a standard size. To remove the shear bolts, I used a cutoff wheel to cut a slot across the tops and a screwdriver, with a blade ground to fit, to remove the bolts. This trick also works to remove the engine ID tag before having the block hot tanked. I used socket head cap screws as my replacement bolts, but have also seen hex headed machine bolts used. Neither bolt type tended to foul the cowl. As I remember it, the plastic switch controls how far the key lock can turn and the two are connected by a metal bar. With the switch assembly off, it is,usually, easy to see what needs to be replaced. Les
Les Bengtson

Thanks for the thoughts everyone.

That is what I will do - prob. what I should have done from the start. Disassemble the thing, figure out what is broken and then decide what needs ordering.
It sounds like Jim is right though, and the blade broke which actuates the switch, then the key would spin around freely, and the switch would stay in the "on" position.

hmmmm. Sounds kinda fun to take apart anyway. That is usually how all my new parts purchases begin.
Jeffrey Delaney

I have an ignition key problem with a '77 B as well. My key won't releaes from the switch. It has a detent bitton to push, but the key is STUCK :-( and won't come out.
Doug Martin

Jeffrey,

I second Jim Mindy's suggestion. This is exactly what happened to my '74 - the blade which connects the key lock to the plastic switch broke. A new part was expensive and availability was questionable. I had much better luck getting a used one. I eventually got it from Les Bengston's friend Bob Shaulin. He sent me an excellent part and I'd call him again in a second.

Doug,

As to the key stuck in the ignition: I heard of this once. The "locksmith" took a wooden mallet, gently knocked the key INTO the lock a little further, and this loosened it up.


Best of luck to both,

Matt K.
Matt Kulka

This thread was discussed between 05/01/2003 and 13/01/2003

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