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MG Midget and Sprite Technical - Cold Cranking

First start of the day is pathetic, I turn the key and the engine crawls over a few times, then speeds up and finally bursts into life, I know the timing and mixture are a bit off, the car is going up to Peter Burgess for a rolling road session to fix that.

I have added two new earth straps, one from the block/dyno fixing bracket to the chassis and one from engine/gearbox/starter bolt to the battery earth bolt on the bulkhead.

The starter is fairly new as is the starter solenoid.

Any ideas or do they all crawl over on cold start, by cold I mean ambient not real winter cold.

1965 AHS, 1275cc, positive earth.

Thanks,

Malc

Thought I'd add a picture for the hell of it !

Malc Gilliver

Nice colour and love the wheels.

Well if it's not earths, you still need to check the battery, and the heavy connections to and from the solenoid, and to the starter motor. Also you say the timing is a bit off. Too far advanced can give you those symptoms.
Lawrence Slater

battery connections are my bet there are a lot of dodgy ones around.
Good ones are a world of difference
Onno K

Lawrence,

Thanks, its Rivera Blue, original wheels, but I think I'll be getting some Minilites soon.

I did wonder about the advance, but once the car has started, it will then fire up fine for the rest of the day.

Onno,

I've tried to measure the resistance of the earth and it so low as to be unmeasurable, the car has an 'old style braided earth lead' from block to chassis, then two new earths as I mentioned in the post, so three good cables two go from the block to the chassis and one is connected to the starter motor bolt and the earth bolt, so I agree it does look like an earth problem, but as I answered Lawrence, once the car has started, it will then start easily all day.

I'm running 15w40 oil btw.

Malc

If you like the colour, I finally got the interior done.

Malc Gilliver

Mmmm. I like it. A very warm pleasing colour that.

I'm a recent convert to minilites, but last year or so, I bought some original steels to put on my '66 Sprite. I bought the minlites as a tempory measure to get rid of the rostyles and I was going to have the original steels banded to more easily/properly take 165 tyres. Now seeing yours resplendant on it's original wheels, have boosted my appetite again. I must get around to it.

Have you also checked the resistance path of the live connections to and from the solenoid and to the starter motor?

Once the engine is warm(ish,) it will always fire more easily than when cold. Less drag from cold oil for one thing. Plus combustion chambers primed with fuel and ready to go. The battery will also be "warmer", and there will be less internal resistance in it.
Lawrence Slater

With a fully charged battery, measure the volts across the battery terminals whilst cranking for 15 seconds - volts will drop, but if they go below about 9.5 then your battery is failing. You will need to disable the car from firing to do this test - so disconnect the coil wires.

Other possibilities are worn starter motor brushes. And there was a reference recently to the starter motor bendix gears - some have 10, some 11 teeth. A 10 tooth one will give about 10 % more torque to turn a tight or high compression engine. Both fit the same flywheel ring gear. Might be enough to overcome your problem as a last resort if you cannot find anything else wrong!
Guy W

Guy that's a new one on me. I hadn't realised there were different numbers of teeth on the bendix. So in order to mesh properly with an additional tooth, there must be "slack" in the 10 tooth setup then?
Lawrence Slater

Lawrence said "Mmmm. I like it. A very warm pleasing colour that."

That made me laugh - Why ????

because....see picture attached

oh and it's Riviera Blue, not my original attempt, clearly has a french blue feel to it.


Guy,

I'll check the battery while cranking and see how it performs.

Thanks.

Malc



Malc Gilliver

Malc,
Mmm like it loads :)
FWIW in my experience the heavy cables rarely if ever fail. By all means check and clean the terminals at each end but my money is on the starter solenoid or a duff starter motor.
Do a volt check at the starter motor and both sides of the solenoid and if there is no noticeable drop or difference at each point try a different starter motor.

Best of....
MGmike
M McAndrew

One good earth lead to the block should be fine.
No more should be needen search for an other fault to fix!

On the positive and negative pole of the batery there should be very good clamps connected to wire of more than enough thickness, with on the other side soldered an eye to eiter bolt to the body for earth or to the starting relay which ever pole you have.

These wires and clamps (both sides) are crucial and with your problem description suspect.

And keep the wheels!!
Otherwise I am willing to take them to the skip for you ;)
Onno K

If when pull the coil lead and try to start it - it turns over at normal speed then it is over advanced. On earlier cars the trick is to pull the starter to get the engine spinning - then turn on the ignition.
F Pollock

Lawrence,

A standard tooth profile may not be used for the 10 tooth pinion or maybe the 11 tooth pinion. They may be altered in order to give correct mesh in the application but have a non standard profile as a result. Have a look at "gear profile shift" if you want some more information.
David Billington

Fergus,

Thank you, it's so obvious once you pointed it out !!

Malc
Malc Gilliver

MMM indeed. I must be physic lol.

So back up for my too far advanced theory then. :).

Agreed, the heavy cables rarely if ever fail, but the connections do.
Lawrence Slater

Thanks guys,

It was too far advanced !

Malc
Malc Gilliver

just changed my 65 1098cc starter and it has 9 teeth on the bendix, why all different. ?
regards bob.
bob taylor

I can chalk up a win then, and share it with fergus. lol.
Lawrence Slater

Yep. you suggested it, I suspected it, Fergus had a really easy way of proving it !

Malc
Malc Gilliver

Win win win then ;).

Now it's driving nicely again, would you mind awfully, driving it down to Kent, and leaving it on my drive? I really do love that colour. It's a really nice looking car overall.
Lawrence Slater

This thread was discussed between 29/07/2013 and 31/07/2013

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