Car starter motor.

[Dave Plowman (News)]

I'm having problems with the starter motor on the old Rover. It's a fairly recent recon unit - but has had a fair amount of abuse since I've fitted an after market engine management system which of course produced starting problems until tuned. And even although it's running well now the injector pulses at cranking are set separately so rather hit or miss to adjust for a very cold start. As the O2 sensor can't help with telling you what the mixture is 'till it's running...

I've stuck my DC clamp meter (not the most accurate of devices) and looked at the cranking current on a cold day. It's saying 550 amps - close to the battery max - and it's turning over slower than I remember. So I'm guessing at a shorted turn somewhere through overheating. Have had this before.

Many Jap cars use a Denso starter which uses a smaller but faster motor and reduction gearing. Said to use a lot less current and produce more torque. And I can buy one with a specially made mounting for my engine. For more than an exchange Lucas one - but not so much as to be out of the question.

Seems to me a win win solution as it's much lighter as well. And of course the lower current will give more volts to the ignition which might help too. And if it should fail, I can get a secondhand motor only and fit that to the adaptor plate for much less than the original cost - I'm told they don't fail often so are cheap secondhand.

Any advice?

[Andy Dingley]

Get the mini motor (I had one on my Rangie). They work, they're often a hell of a lot easier to fit to a big '80s lump as starters of that period had grown huge and unwieldy. Just saving an hour's spanner work can make it worthwhile (Volvo 960!)

Land Rover may carry them as cheap spares on a straight exhange. Many of these old motors aren't refurbed for exchange any more, they give you a geared mini style instead. Work enquiring, if you have a friendly spares duffer.

[Huge]

I had a Bosch Heavy Duty starter motor fitted to my RV8 powered TVR because of slow cranking problems, especially when hot, about 4 years ago and it's been fine ever since.

[Roger Mills]

I don't understand that - it appears to defy the laws of physics! So the motor itself runs at higher speed and lower torque - working through reduction gearing - but the engine needs a certain amount of *power* to crank it - based on the product of cranking torque and cranking speed. The starter motor has to produce that power , so - unless it's dramatically more efficient - it's wattage will be the same as the original Lucas motor. Since watts = volts x amps, and you can't do much about the voltage, then surely the current is going to be the same?

[Dave Plowman (News)]

I *think* it's because a series wound motor isn't very efficient at stall or close to that. They are very much better at their natural quite high speeds. I've been told the Denso has a permanent magnet motor but can't confirm this. Certainly old car wiper motors etc used to be series wound, but changed to permanent magnet when better ones became more affordable.

[Dave Plowman (News)]

I *think* that's what later Rangies etc than my engine use - certainly a neighbour's one whizzes round compared to mine. But I've been told they don't make one which fits the SD1 - the solenoid is in a different place, and would foul the exhaust.

[Dave Plowman (News)]

Yes - it's not an easy job on the SD1 either. So just being so much lighter will help.

Sadly the SD1 uses a different design - the solenoid is in a different place to clear the exhaust.

[Jules]

Hmm, I dismantled our truck one last year - the bearings had all gone dry (the exhaust runs right next to it) and a seal had failed such that it was slowy filling up with crud. It was much better afterwards :-)

Are you certain it's not the battery or wiring issue? Any minor problems can really mess with starting even if there are no signs of trouble when things are running. I realise you've probably looked into it already, but it doesn't hurt to ask - changing the starter is expensive faff if it turns out to not solve the problem (or mask the real one)

cheers

Jules

[Jules]

Bah, real engines use coffman starters or compressed air ;-)

[Dave Plowman (News)]

Yes - I've cleaned and checked all the connections including the grounds. The high current suggests a shorted turn somewhere in the motor due to overheating. Remember we're talking Lucas here. ;-)

[Andy Champ]

Real engines have maximum torque at zero revs, and don't need starters :P

Andy

[Adrian]

"Dave Plowman (News)" gurgled happily, sounding much like they were saying:

A few years ago, I had a replacement starter on the old CX - and it was a reduction gear type. It was astonishing how much more quickly it spun it over. No probs with it before I sold the car.