Lotus Elan

Starter motor fault check list

PostPost by: bob_rich » Fri Apr 13, 2018 6:44 pm

Hi

Just been reading through the post and you seem to have been checking the battery and the leads OK.
A short in the motor is quite possible. I had a very similar fault a while back and it turned out to be that the insulated bush that takes the 12 live through the rear of the starter motor had melted and the 12V was shorting to the case when the solenoid operated, but in view of the high current taken on starting this "short" was well not that low a resistance. So the starter motor sort of pulled in, volts from a good battery really dropped low and engine did not crank. I took out the motor confirm the bush was low resistance and replaced it then all was OK. However a bit later the solenoid packed up but I was able to strip in down ( drilled out the rivets) clean it up there was quite a bit of burning on the contacts then reassembled it using m3 screw and nuts and then all was well.

I actually checked how the starter performed by measuring the current while trying to start and wrote it up in my rebuild diary have attached it here for interest.

Hope it helps best of luck

Bob
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PostPost by: MarkDa » Fri Apr 13, 2018 11:24 pm

Having remade the main feed cable I mentioned a few posts ago, I still didn't get much any go out of my starter.
So I thought it must be the earth in boot and cleaned/tightened up - still no go.
But hang on, this is a bolt through a bobbin, maybe it isn't tight against the chassis?
And that's just what it was - a couple of twists on a socket (after releasing the silencer mounts of course!) pulled it up nicely - job done.
So it's not just a case of ensuring the earth cable is attached to the bolt but that bolt is connected to the chassis.

Most of the points we've been raising were in a thread this time last year.
My eventual solution was suggested by Eric Bushby in the first response within minutes of the problem being raised.
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PostPost by: ericbushby » Sat Apr 14, 2018 9:43 am

If it is, as they say, that 90% of carburettor problems are actually caused by ignition, then 95% of electrical problems must be bad earth connections,
Well done
Eric in Burnley
Edited for punctuation mistake
Last edited by ericbushby on Sat Apr 14, 2018 4:55 pm, edited 1 time in total.
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PostPost by: jimj » Sat Apr 14, 2018 10:22 am

Right, so, noticing that the earth wire across the engine mounting under the exhaust looks unsubstantial I was thinking, maybe, that was the issue. Good old ebay posted me a 9" braided earth strap so this morning I`ve connected that from the starter motor mounting bolt directly to the chassis. I cleaned up the holes with a dremel for a really good contact and it`s made no difference.
Then, disconnecting the battery, with jump leads I connected the starter motor directly to a different car but nothing happened. It looks like a faulty motor then but before I remove it I had another check with my voltmeter. Over 12 volts at the battery, virtually the same across the solenoid, but at the starter motor when I try to crank the engine I just get a click from the solenoid and less than 1 volt at the motor. The solenoid got really hot really quickly. Can both the solenoid and the starter be faulty? Surely that`s too much of a coincidence.
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PostPost by: billwill » Sat Apr 14, 2018 10:37 am

If there is only one volt left at the motor it is probably drawing an enormouse current. Enough to make the solenoid hot.
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PostPost by: billwill » Sat Apr 14, 2018 10:39 am

MarkDa wrote:Having remade the main feed cable I mentioned a few posts ago, I still didn't get much any go out of my starter.
So I thought it must be the earth in boot and cleaned/tightened up - still no go.
But hang on, this is a bolt through a bobbin, maybe it isn't tight against the chassis?
And that's just what it was - a couple of twists on a socket (after releasing the silencer mounts of course!) pulled it up nicely - job done.
So it's not just a case of ensuring the earth cable is attached to the bolt but that bolt is connected to the chassis.

Most of the points we've been raising were in a thread this time last year.
My eventual solution was suggested by Eric Bushby in the first response within minutes of the problem being raised.



To me that sounds as if the earth strap from the battery is going to the wrong bolt. Surely there is a bolt in the boot which is direct into the chassis.
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PostPost by: Elanman99 » Sat Apr 14, 2018 11:58 am

jimj wrote:Right, so, noticing that the earth wire across the engine mounting under the exhaust looks unsubstantial I was thinking, maybe, that was the issue. Good old ebay posted me a 9" braided earth strap so this morning I`ve connected that from the starter motor mounting bolt directly to the chassis. I cleaned up the holes with a dremel for a really good contact and it`s made no difference.
Then, disconnecting the battery, with jump leads I connected the starter motor directly to a different car but nothing happened. It looks like a faulty motor then but before I remove it I had another check with my voltmeter. Over 12 volts at the battery, virtually the same across the solenoid, but at the starter motor when I try to crank the engine I just get a click from the solenoid and less than 1 volt at the motor. The solenoid got really hot really quickly. Can both the solenoid and the starter be faulty? Surely that`s too much of a coincidence.
Jim


You have all the things you need to find out where the missing volts are.

Presumably when you measure the battery volts you are connecting the meter probes directly (or near to ) the battery terminals.

When you measure the '1 volt at motor' where are the meter probes? If they are both close to the motor, say the on motor terminal and the engine/motor metalwork, then (forgetting the solenoid for a minute) you cannot know if the 11 volts is being lost in the positive or the negative leg. The point is you know something has a voltage drop across it but you dont know what.

The solenoid gets hot. Well is not meant to be a heating device but there are two ways it would get hot. One is the actual coil. Its only intended to be energised for very short periods, if you energise it continuously it will get warm, if its energised for minutes I'm sure it would get very warm and eventually get hot. The other thing that would make it hot is if a large current was passing through one of its terminals or contacts and that terminal or contact was in less than perfect condition. If one of the ring tags was oxidised and not making good contact to the solenoid stud than that would get hot, very quick! It would take a while though for that heat to spread through the whole solenoid. So a lot depends on the interpretation of 'hot'.

One quick test which (would nearly) eliminate the solenoid contacts, is to use the screwdriver/spanner method to bridge the two solenoid studs, if you still have the one volt at the motor the solenoid contacts themselves are probably OK.

If the battery is in good condition and the 11 volt drop is somewhere in the whole current loop the actual current flowing must be really high, if the current was low it would not be producing heat.

I still say that the simplest way to identify which is the faulty joint is by measuring 'across' each joint or metal to metal junction.

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PostPost by: jimj » Sat Apr 14, 2018 2:26 pm

So, before I replace the starter motor, which is where the fault lies I`m pretty sure, I have one more thing not yet suggested: If I remove the positive from the starter motor and check the voltage from there to earth when the ignition key is turned as if to start the car, shouldn`t I get 12 volts? If so wouldn`t that confirm that it is the starter motor?
Jim
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PostPost by: Elanman99 » Sat Apr 14, 2018 3:09 pm

Jim

If you do that test and get the 12volt reading it will prove is that your meter is working.

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PostPost by: Elanman99 » Sat Apr 14, 2018 3:18 pm

Jim
You may have a faulty starter motor but why replace if you dont actually know its faulty?

Not so much nowadays as cars have a lot of electronics and diagnostics, but garages used to find it easier (and more profitable!) to replace the plugs, points, capacitor, distributor cap, rotor etc, etc, rather than finding out what the cause of a misfire was, after all the customer paid, and generally believed whatever the mechanic told them.

Finding the actual fault with your starter system is simply done by measuring voltages, no special equipment required, just use your meter directly across each metal to metal junction.

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PostPost by: MarkDa » Sat Apr 14, 2018 3:32 pm

Jim
As Ian says without any load voltage at end of starter cable doesn't really tell you anything.
However your starter won't play even when connected direct to an alternator boosted battery - so it probably needs attention.
Until you get it off and tested there's no saying that it needs replacing.

It may repair depending on what's wrong and either your or repair shop skills.
There's a school of thought that reckons old starters are better made than new ones and worth renovating.
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PostPost by: Craven » Sat Apr 14, 2018 3:47 pm

Finding the correct starter with a 9 tooth pinion may be easier said than done! The starters on offer I?ve seen, that is internal inspection before fitting, are pretty poor.
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PostPost by: Bud English » Sat Apr 14, 2018 3:53 pm

Edited after another re-read of the thread. Sounds like you're on your way to having it sorted.
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PostPost by: MarkDa » Sun Apr 15, 2018 12:10 am

Edited as duplicate
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PostPost by: MarkDa » Sun Apr 15, 2018 12:23 am

Earth bolt in boot.

I've a sprint and there are no tapped holes in the chassis under the boot.
There are two bolts through the very rear of the chassis into body bobbins and then through to boot with nuts.
One has battery earth and the other is rear end low current earth.
When I put the new chassis in did bolts up tight enough to get current to flow ok.
But with the passage of time the contact reduced sufficiently to allow low current but not enough for starter or even cooling fan.
Cleaning and tightening in boot not enough; but as soon as I pulled the body down a bit more contact was restored.

I think this came about because the freshly undersealed body was a fairly tight on the turrets and as we're advised not to pull body to chassis I just nipped bolts up - then the body settled a bit more with use.
Thereby reducing contact between bolthead/washer and chassis.

Anyway the starter now churns for England!
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