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Sledgehammer

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Just found the board today and think it's great! I bought a 64 MGB from a friend. It had been sitting in an airplane hangar sleeping since 1988. I rebuilt the carbs, brakes and clutch hydraulics and she's almost ready for the road. I'm having a problem with the starter though... she cranks, fires once and then it sounds like the starter spins down. I have to wait for the starter to stop spinning to re-try cranking. Eventually, she'll fire more than once and start on up. One of you car buffs have an explanation for this and how to fix??? Thanks in advance.
 
I don't have an answer to your question, but welcome to the board! Always great to have another Mark I here.
 
My first 'B was a '64 in '70!! I put about 200,000 miles on the car and only freshened the engine once!! When I sold it, it had 269,000 miles on it!! It had been to Mexico, Prince George, Calgary, Phoenix, Salt Lake City and countless other places!! What a car!!!
Your problem is probably a weak bendix spring!! You just need a new starter drive, or if you are worried about the starter, just get a new starter!! GOOD LUCK BUDDY!!!!!!
cheers.gif
 
The fact that the starter is turning the engine over says it's worth saving. I think before spending money to buy a new starter I would take it off of the engine and disassemble it.
Check the condition of the brushes (do they seem to have good spring load and is there a fair length to them or do they look like little stubs?). They are cheap to replace.
Is the mica separators between the copper communtataor bars flush with or above the copper surface? If so, file or cut them back down below the copper bars.
Are the gear teeth on the drive pinion chipped or just rounded off. If the edges are just rounded off it is no real problem. If a tooth is partially or totally missing it means replace it (along with the rest of the starter).
The Bendix spring (on the drive pinion gear) must not be broken but I haven't known one to really wear out unless it breaks.
Clean the inside and oil the bearings with a good 30 weight oil.
Reassemble and think about what can be done to keep the engine running on the first start.
Jim
smile.gif
 
On rereading, I wonder if your 'run' circuit is working?? Maybe it is just firing in the start position and when you back off the key it is dying!! To check this, try leaving the key in the start position for a little longer!! If it still dies, then it is not the problem!! Oh!! I have seen those bendix springs get weak in the old Austins!!
 
Hello Sledgehammer,

I recently read about a similar problem on a Triumph group on Yahoo. The reply, which turned out to be correct was very low compression. So it is worth a check.
In contradiction to XK4's advice, all the manuals I have tell me not to undercut the commutator on a starter motor. I know it is normal practice on most DC machines but not for starter motors.

good luck.
cheers.gif
 
Your car has the old syle starter that spins in/out through a hole in the transmission...probably ready for a rebuild as the main or pinion springs are getting weak...believe main spring is available but pinion isn't...take it by your local automotive electric repair shop & have them bench test it...if they can't repair, several of us have good used ones...though I've stopped bench testing them myself & am gonna start going to the professionals & paying their small surcharge!
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>In contradiction to XK4's advice, all the manuals I have tell me not to undercut the commutator on a starter motor. I know it is normal practice on most DC machines but not for starter motors.

good luck. [[cheers]]
<hr></blockquote>

I haven't read that before, but I have read "Automotive Electrical Equipment" by William H Crouse, McGraw-Hill 1963 pp188-189 (Cranking Motor Service) which says "Undercut the mica after turning down the cranking-motor armature commutator. For this operation either a milling cutter may be used, a hack-saw blade ground down to the correct thickness, or a cutter installed in an electic drill..."
Although the copyright is rather old, so are most of the LBCs on this forum.
Please note, I am only adding this answer so the people working on their car won't be misled.
Oh, and why would a sane person read the above book? It was required by the 200 level class at Arizona State University for a Secondary Education Technical Education Degree I recieved. (High School Auto Shop is the more common name).
Jim
smile.gif
 
YUP!!! You should always cut the mica back!! A hacksaw blade is painful, but it does work!! My buddy just does it on his lathe!! Real easy!! Just rotate until it lines up and roll it back and forth a couple of times and it is cut in!!
 
I've never tore down a Starter. I've got a good mindset for working on cars and understanding what's going on with them, just not a lot of experience. I have no idea what a "mica" is or a "commutator" for that matter. I just plan pulling the starter and taking it to a rebuilder here locally.
 
Take it apart, look at it and you will see!! Then take the pieces to the rebuilder, he can put it together with his eyes closed!! Have fun!!
 
Alec,
What is the reason/theory for not undercutting?

Gary,
What is the reason/theory for undercutting?

It must have something to do with the relative wear rates of mica & copper & the hardness of the brushes. If copper wears faster than mica I can see a reason for undercutting. Do they still use mica nowdays or just long ago. I have seen a lot of commutators on large generators & motors that are never undercut. I know that the brushes for large machines come in different hardness grades. I wonder if the original reason has disappeared with the advent of new insulating materials & brush materials.
D
 
Thanks for everyone's input. I suspected a problem with the starter but before I pulled it, figured I'd post here. I'm in the Fort Worth, TX area. Can anyone recommend a good shop for rebuilding the starter?
 
Hello all,
Re undercutting.
this is really another topic, but firstly let me say that I served my time as an Electrical Fitter so am used to DC machines, where it is standard practice to undercut all commutators.
However, and I repeat, as far as LUCAS starter motors are concerned my manuals (plural) all say do not undercut. I don't know why, but they are a very heavy current machine as is evident by the construction and by the very significant copper content of the brushes. My guess it's to do with the very hard brush material so as to have a reasonable service life for the commutator.

By the way, SH, how is the compression on the engine as that really was my point in my post.

Alec.
cheers.gif


[ 09-12-2003: Message edited by: piman ]</p>
 
I wouldn't cut the commutators, especially with a hacksaw blade!....oh, I've about 2 dozen used starters that are going to the shop for bench testing next week...several are the early style
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Dave Russell:
Alec,
What is the reason/theory for not undercutting?

Gary,
What is the reason/theory for undercutting?

It must have something to do with the relative wear rates of mica & copper & the hardness of the brushes. If copper wears faster than mica I can see a reason for undercutting. Do they still use mica nowdays or just long ago. I have seen a lot of commutators on large generators & motors that are never undercut. I know that the brushes for large machines come in different hardness grades. I wonder if the original reason has disappeared with the advent of new insulating materials & brush materials.
D<hr></blockquote>

That is what it is!! When you look at a worn armature you will see that the mica sits a little higher!! I wonder why Lucas says not to do it?? Oh well, makes rebuilding a Lucas starter or generator that much easier!!
cheers.gif
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr> I've never tore down a Starter. I've got a good mindset for working on cars and understanding what's going on with them, just not a lot of experience. I have no idea what a "mica" is or a "commutator" for that matter. I just plan pulling the starter and taking it to a rebuilder here locally. <hr></blockquote>

Perhaps taking it to a rebuilder is the best idea, but to answer the question about mica etc.
The commutator is a bunch of copper bars on the armature. The carbon or carbon/copper brushes conducts electricity into the proper wire windings on the armature (which creates a electromagnet). It does this by making electrical contact with the commutator bars.
The bars must be insulated from one another so the electricity goes to the proper windings. To do this, old DC motors used mica (a moderately soft, non conductive type of rock which doesn't mind very high temperatures) between the bars. The copper bars are quite soft so they wear faster than the mica. If the mica is above the bars,the carbon brush will ride up on it so it cannot make good electrical contact. That is the reason the mica is cut down below the commutator
The only reason I can think of for not cutting the insulator (mica) back is really hard brushes (Lucus?) may tend to schmear the copper across the insulation gap to the point that it contacts the adjacent bar?? This would short out the armature.
Anyway, have fun with your car.
Jim
smile.gif
 
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