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MG MGB Technical - Possible starter issue?

This has been happening for quite some time. I had the starter rebuilt and when I last pulled the lump I inspected the ring gear which was fine.

Here's the issue:

When its hot out and I turn the key I get - nothing. No click. Nothing. Sometimes if I ‘rock’ the car in gear it then cranks. This last summer none of that helped and I had to gravity start it. Any ideas?

All electrical connections have been cleaned and checked, btw. Its a mystery.
Max71

Max
I take it that it is a later MGB with the pre-engaged type starter with the solenoid on the side of it
I've had a few of these that the solenoid sticks on when they get warm and there isn't enough current flow through the ign. switch to overcome it
I suggest you fit a relay to reduce the load on the ignition switch

Another cause could be sticking startermotor brushes but if you have had the starter rebuilt it shouldn't be that
To test for sticky brushes,Next time it won't go get your favourite helper to hold the key in the crank position and give the starter a little tap with a small hammer, if it starts cranking, it's probably brushes causing the problem

willy
William Revit

My apologies. Yes, a 1971 with the solenoid on the outside. I'll have to look at the wiring to see where to best fit the relay. I have them on the lights after yet another light switch melted down and no need for that.

Do you think I should just go for a different style? Say a gear reduction starter? A local company sells ones that look just like the original style.

http://www.northwestimportparts.com/MGB-Upgraded-starter-with-solenoid-68-80-d335.aspx

Or will I always have the issue unless I install a relay. BTW, what specs do you recommend on one?

Its an old problem that you accurately described. Good to know its reproduceable.

Thanks for the input.
Max71

Just went to the wiring diagram to look for best place and it shows a starter relay as built in...

or are you suggesting an additional?



Max71

Max

Before you start replacing parts I'd suggest trying to isolate where the issue is, I know this means waiting for the car to fail but the alternative is never knowing whether you've fixed it or not.

You can eliminate the relay easily, I could explain it but John Twist does a much better job than I could. Use the link below and FF to 3.30 if it still doesn't turn over it's the starter, if it does it's the relay, ignition switch or wiring. Good luck

https://www.youtube.com/watch?v=jVxIW_pImjw
R.A Davis

for some reason it didn't make it a hyperlink so you'll need to copy and paste it into your browser.

I'll try again to see if this one works.

https://www.youtube.com/watch?v=jVxIW_pImjw

R.A Davis

brilliant I'll give that a go. i think the relay is pretty new so shoud be interesting
Max71

If the solenoid is being powered but not moving then there should be some slight dimming of lights and a small volt-drop. This is because the pre-engaged starter has a pull-in winding that takes about 30 amps. Once the solenoid contacts have closed that winding is bypassed and leaves the hold-in winding taking about 10 amps.

As a 71 it should already have a starter relay, mounted by the fusebox. This was provided at chassis number 187170 i.e. the start of the 69 model year.

If you don't even get a click from the relay when you turn the key to start, then it is the relay operate circuit that is the problem i.e. 12v on the white/red from the ignition switch, or earth from an earthing point nearby, or the relay itself is intermittent. There is another possibility and that is a bullet connector in the white/red about half-way down the tail to the starter. This is the for automatic gearbox inhibiter switch (where provided) and is between the ignition switch and the relay.

If the relay clicks but there is no clonk from the solenoid then the problem is with the solenoid circuit i.e. 12v to the relay on the brown, the relay contacts, 12v from the relay on the white/brown, connection to the solenoid, or the solenoid itself.

Starting after rocking in gear is probably nothing more than disturbance of a bad connection somewhere.

That starter is the ad says - it is lighter, smaller, quieter, takes less current, and spins the engine faster. Not quite as good in all those areas as a geared starter, but in the UK at least they are half the price of an OE and a quarter the price of a geared.
paulh4

To make a clickable hyperlink, you need to remove the 's' from https

http://www.youtube.com/watch?v=jVxIW_pImjw
Dave O'Neill 2

Max
Sorry mate, my appologies
I should have said replace/check the solenoid not fit a solenoid as there is already one in the system
Bit of a blonde moment on my part
Cheers
willy
William Revit

Firstly, thanks you to all.

Willy - no worries. Why I had to check the schematic to remember the relay shows I didn't have that in the equation.

RA & Dave thanks - I checked it out. I'm going to remember (or write it down) for future reference. When I used a starter switch for doing the valves in the past I used a different location.

Paul - very thorough. Sometimes I would only get a 'click'. Other times absolutely nothing. I'm going to hunt down that white/red and see what I can find. I used that bullet connector brush which I guess is just a gun brush to that diameter. Works quite well.

"Not quite as good in all those areas as a geared starter" -- can you elaborate on that for my education? Do you mean this one from Moss? Or just the plain original. My engine, by mistake is 10:1 compression.

http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=34594

Max71

"Sometimes I would only get a 'click'. Other times absolutely nothing."

This indicates you have two intermittent problems in the starter circuit, if neither scenario resulted in a cranking engine.

In my experience with all three types of starter the OE is large, heavy, noisy, takes a lot of current, and cranks relatively slowly albeit fast enough to start under all normal circumstances of course.

The modern equivalent is smaller, lighter, quieter, takes less current, spins maybe a little faster than the OE, and is half the price of an OE. By taking less current is is putting less load on the battery, which should increase its life, as well as giving you a better chance of starting the car in adverse conditions.

The geared is probably slightly smaller than the modern equivalent, perhaps a little heavier, is even quieter, even less current (and even less load), and even faster. However it costs double the OE and four times the price of the modern equivalent.
paulh4

Ok, first I'll trace. When it gets warm, when the fault occurs I'll try to eliminate parts as the source. If I need to replace the starter I'll go with that more modern one which is a decent price.

If the car has been sitting like this winter I like to use the starter to get the oil pressure up prior to firing. New should be easier as you said on the battery for this.

Again - much appreciated.
Max71

Max
Just for testing purpouses, you could hook up a test globe between the small solenoid exciter wire on the starter motor and earth
The globe should light when cranking
When the fault occurs ----
If the globe lights but the starter doesn't operate, the fault will be in the starter itself
If the globe doesn't light while trying to crank it means the fault is back from the starter and then the globe will need to be fitted on the other side of the relay so you can determine if the fault is either no power coming from the ignition switch to the relay or the relay itself failing

willy
William Revit

If Max's is as intermittent as mine was a test-lamp (or meter) is no good unless it is wired into the circuit so you can see it each time you crank. Took a while moving it from battery connector to battery cable stud on the solenoid to motor stud on the solenoid to prove it was the solenoid. However in my case I always got the loud solenoid click, just very occasionally no crank.
paulh4

Agree Paul
My intent was to have it hooked up to the starter initially and have it there ready for when the fault faults and progress on as needed
willy
William Revit

This thread was discussed between 10/02/2017 and 13/02/2017

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