Battery drain/won't start when damp

[str160]

Morning folks,

Car is a 1989 mk1b. Only had since xmas.

Issues are it won't start or the battery drains. For example the car was left over night Friday, it 'just' started on Saturday, I did some garage stuff, tried to start again, and nothing...then about an hour later it chugged over and fired.

So this morning, pressed for time because I'm at work, I go to start it, and nothing. So in the past I've just jump started it and it fired up ok. Tried that this morning, and got zip. It was like it wasn't even connected to a running car.
It turned over but then died off.

I'm thinking possible bad earth or dying alternator.
The battery is charged/ok(this is definitely not the issue).
After market alarm fitted but I haven't been setting it due to this issue.
Nothing obvious as far as I can tell.

Any other ideas? Thanks.

[PW@Woodsport]

How can you be so sure the battery is not the issue? When they go bad they won't hold full charge overnight.

Get the car running again (by whatever means) and check the charging rate, if it's around 14v then your alternator is good and you either have a draining issue or battery problem. If you put jump leads on and it starts then there is nothing wrong with your earthing or starter circuit.

To test for a drain set your meter to Amps and connect the meter in line between the battery + terminal and the battery, it should not show more than 0.1amps, make sure all the doors are closed/interior light is off as this will cause an instant 1 amp drain.

If your drain is acceptable and charging rate is ok AND the engine starts when being jumped then you do have a faulty battery.

Hope that helps you out.

[Peter Gidden]

Check alternator charge rate.

Get battery drop tested. The winter weather will kill a a battery overnight.

[XLarge]

Dead alternators are a common problem on the Mk1 as well as dead starter motors.

The alternator sits direkt under the drain sheet of the engine door. Mostly this shorten the live of the alternators bearings.

The starter is getting grilled by the exaust manifold. On the Mk1b it is possible to use a starter from a 4A-FE engined car that sits on the other side of the engine, but this modification need some modifications on the dust cover and the wiring.

But as Paul said, check out the batterie and the charge rate at first. It´s the always the first suspicious.

[str160]

Hey folks,

Battery is fully charged/checked. Tried two. Same situation.

Car is fitted with a Microscan alarm. I might try disabling this.

With a fully charged battery, nothing else running, I turn the key, the starter fires but then dies off right away with a dimming of the dash lights.

I did check the voltages as per Jimi's guide on MR2oc. Voltages were equal on the 3 pin plug and the main connector was reading a bit higher. I think the readings on the 3 pin were around 10v though, so I'm guessing this means it's a wiring issue somewhere.

[MartG]

Try cleaning all the engine earth connections, especially the big one that connects to the gearbox near the thermostat. Corrosion on these ( at either end ) will affect the ability to start

[jimi]

The alternator sits direkt under the drain sheet of the engine door. Mostly this shorten the live of the alternators bearings.

I keep reading this and it's just not true ! another MK1 myth
Have a close look at the under tray on the engine cover and you will find that it is designed to direct any water to the top of the cooling system expansion tank. Inspection of the tank will reveal that it has a black plastic trough bolted to the top of it.




This in conjunction with the shape of the top of the tank diverts any water to the back of the expansion tank where it runs down the rear bulkhead well away from the alternator If you can't be bothered checking it out, just have a look down through the vent on the engine cover (with it closed) can you see the alternator ?
Mr T isn't daft you know

[PW@Woodsport]

I'm not convinced either way Jimi, i know the alt bearing failure is not the reason they fail, we both know it's the windings siezing against the brushpack that is the cause of that, but wether that's down to water ingress or not i cannot say for sure..... water has a habit of clinging to underside surfaces and then dripping off, so it could well be finding a path from the engine lid vents to the alt, i agree with you there is no direct route though.

Mk1s do suffer an abnormal amount of alt failures though, so something is accelerating their demise.

[jimi]

Mk1s do suffer an abnormal amount of alt failures though, so something is accelerating their demise.

I certainly wouldn't argue with that and from what I have seen it's water/damp/corrosion that causes the problem, quite how it gets there is the real mystery

[elbon50]

Yes, my car is on it's second replacement jenny now and has only covered 60K miles frrom new

[un1eash]

I'm on my second alternator, water finds a way somehow, after a big rain fall i've check the engine bay before and found water drops on the aux belt.

[munter]

Just a quick thought...

I had something like this just after I got the car. Went through all the checks and was well puzzled until someone pointed out that I may not be rotating the ignition key fully counter clockwise before removing it (need to press the little button down as well.)

What was happening was i was leaving the clock/stereo etc all on with a big drain on the battery!

Now I go all the way before pulling out and the problem is fixed!

Cheers

[stenky]

You can remove the key before you press the button?

[elbon50]

You can remove the key before you press the button?

I've had my car 15 years Stenky

Most of that time the key could only be removed after pressing the button

Now it can be removed without

Seems that the lock must have some internal wear ?

[stenky]

Has to be that way. Maybe someone has modified that lock barrel.
Both my cars have to have the button pressed and the key fully turned in order to remove it, but the second one sure has some wear in it as I have to wiggle the key until I am able to turn the key clockwise. This is driving me nuts every time I want to start the car

[str160]

I'm back...

So, I stuck the battery on charge Monday lunch time, got home, shoved it in, and the car fired. OK.......

Checked voltages at battery, Alt plugs, fuses, etc. All reading ok (Battery shows 14.6 when engine running, 12.5 ish when off).

So I've taken to disconnecting the battery if I'm leaving it for a few hours, and checking the voltage before and after, and the battery isn't dropping anything worth mentioning even after 24 hours left alone.

I've now left it for the past couple of hours connected, and will check the voltage when I leave work.

So it looks to me like something is draining it when stationary.

[elbon50]

Did you press the button & rotate the key all the way anticlock before removing key STR ?

[str160]

Indeed I did.

[PW@Woodsport]

Bear in mind when you're checking the battery that even an almost flat battery can show 12v, you need to put it under load to test it, your starter motor is a good way of checking it still has good amps, assuming there are no other faults.

[str160]

With the engine running around 2000rpm, the battery voltage was 14.6v.