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2.25 NAD doesn't start when cold


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I have a 2.25 NAD 3MB '88 S3 diesel.

It doesn't like starting when the weather is cold. It always started/ran fine when it was a bit warmer but won't crank when cold.

I have tried 5 different batteries on it now, including 2 new ones, one of which has 650CCA on it. I bought this battery (after trying a 510CCA battery which wouldn't start it), put it on the car, and it started the car fine. I then secured it and tried again...fine. Excellent, it's finally fixed.

This morning...run the glow plugs....turn the key and the familiar woooh woooh woooh slow starter and no starting. After a quick jump it fired up fine.

The alternator light goes out as expected, and the internal ammeter shows current going into the battery when the engine is running. I have double checked and there is no drain on the battery when the car is switched off, in any case I have tried leaving the battery disconnected over night to no effect.

I can only assume that, for whatever reason, the car draws too much current when the car is cold. Duff starter perhaps? I have noticed that the glow plugs remain on when the starter is cranked, is this normal?

Thanks in advance for the help.

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So it cranks rapidly when you jump it - where do you connect the earth lead? Is it to the engine - in which case your problem is an earthing one.

Otherwise is the thing charging properly? Rough test is do the indicators sound lively when flashing or slow and dead? Much the same with the wipers.

After standing overnight a good battery should be about 12.6 volts, average 12.5 and poor 12.4. When running and settled the voltage across the battery should be 14 - 14.4 volts.

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The car has yet another battery on it now, a known, good, 1 year old 680CCA one.

When jumping I connect battery to battery (which I am aware is a big naughty).

It always starts easily when jumped. The glow plugs are new, about 3 months old. Since the car starts I assume they are fine. I drove the car in to work this morning; left it for 1 hour then went back out to it, it started fine by itself off the battery so I assume the battery is charging fine otherwise it wouldn't be able to do that. The car wouldn't not start without a jump this morning, the starter was very slow indeed and I drained the battery to the point where the starter wouldn't even engage.

I disconnected the glow plugs this morning with no effect.

From what I can tell either the starter is drawing a huge amount of current when the car is cold or the battery is draining overnight.

I don't really see how the starter could be faulty given that the car always jumps well. I'm sure if I went out to it now and tried to start the car it would go easily.

I am going to try again disconnecting the battery when leaving the car. Although I have double checked the drain on it (by connecting a multimeter between the battery and the -ve cable) and it has shown 0 both times something must be happening. I have tried disconnecting the battery before to no effect but perhaps that particular battery was faulty.

Thanks for the advice.

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I was wondering if you were connecting the earth jump lead directly to the engine - if you were it would point to an earthing problem.

Its possible that the vehicle isn't charging properly. Alternators tend to charge at about 11 volts when a rectifier diode fails - and while everything works it does so rather slowly (wipers are slow, heater feeble, lights dim, flashers very slow.)

Dynamo systems can suffer as well - it may be possible to re-set the regulator but this needs a voltmeter and the detailed instructions.

Its also possible that something electrical is staying on - in which disconnecting the battery may prove the point.

Have you got a multi-meter? If not I'd recommend buying a cheap one for less than £10 and getting a few voltage readings.

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Batteries produce less current when cold, and your engine oil is thicker when cold. So it might be that your electrical system is not quite up-to-scratch, but good enough when warm. When cold, it drops just below the line required to do the job.

I agree that checking the charging system would be a high priority. Another test would be to leave it on a battery charger overnight, and then see if it will start several times in a row in the morning. If it will, then it's probably the charging system. If it only starts once or twice, then it's more likely a dodgy starter or wiring somewhere (or your battery is only taking a surface charge).


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I tried disconnecting the battery today at work, even after only 8 hours or so the starter was spinning noticeably more slowly, to the point where, again, it would not start and had to be jumped. The battery had been disconnected during the day. The battery had successfully started the car by itself after the journey to work (I drove to work, stopped the car, left it for an hour and it cranked/started fine). I will check the voltage across the battery with engine running tomorrow. I hope it is just that the alternator isn't giving out enough juice, alternators are one third the price of starter motors and much easier to fit!

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  • 3 weeks later...

I would start by taking some voltage measurements before throwing more money at batteries, alternators or starter motors. A cheap multimeter will do. Naturally, the engine should be running.

  • Voltage across the alternator - output terminal to case or engine block & output terminal to chassis
  • Voltage across the battery terminals
  • Repeat the above under no load and under full load (lights on, etc)
  • Also measure the voltage directly at the battery terminal posts (not cable clamps) while cranking

There should be a good 13.5V or more across the battery, and similar across the alternator while charging (14 - 14.5V with some types of alternator). If that is fine, then it is time to look for voltage drops while cranking (may require 2V or 200mV scale)

  • Negative battery terminal post to engine block
  • Positive battery terminal post to battery terminal on the starter solenoid

These tests highlight poor connections if there is more than a few hundred millivolts in either. It is then a matter of probing across each of the joints in the suspect lead - battery post to clamp; clamp to cable; etc.

It is quite feasible that the starter motor is past its best and might benefit from refurbishment. However, the 200/300 Tdi starter motor is a direct replacement for the S3 type and spins the engine more freely without hammering the battery - it worked a treat for my 2.25 diesel.

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I had the same issues on my 2.3 days, it was a knckered starter, the brush plate was knackered and lots of the current was being lost in loose rivits instead of passing it to the brushes. I Fixed the starter and it used to start even when left for days out in the cold. The tdi started is a good upgrade.


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Thanks for the reply.

There was nearly 2V between the body of the starter and -ve terminal of the battery when cranking, running a jump lead between the engine lifting eye and battery helped, but not enough.

I get 13.9 volts across the battery with the engine running.

12.5+ volts across the battery with no load.

When the weather gets a little better I will have the battery checked (although it seems fine. My charger says it's OK, and it works fine in other cars) if the battery checks out OK I'll change the starter. I do actually have another one; it happens to be attached to my other SIII but it'd be worth swapping them over to make sure it's definatly that.

Thanks once again for the replies. It's so frustrating because the engine runs very well once it's going, and starts very easily when jumped.

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  • 1 month later...

Sorry for the thread resurrection, but thought this might be helpfull.

This issue tured out to be the starter. The clue was when I recorded 2ish volts between the outside of the starter and the -ve terminal of the battery, this means earthing issue or a worn starter. In my case adding a seperate earth did not help.

New starter in (much easier then you'd think, and no need to mess about with the exhaust as the Haynes manual suggests) and it's spinning much quicker then the old one did, even on a good day. It sounds totally different!

Thanks for the replies.

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