Hi-torque starter.

DaveEFI · Post by **DaveEFI** » Tue Mar 18, 2014 9:26 am

I have one of these fitted to my SD1. Can't remember who made it - I imported it from the US. It looked beautifully made.

Problem is it often refuses to engage - turn the key and the motor spins, but not the engine. Worst when cold - when hot it will usually engage first time.

I've had the starter relay circuit apart and am pretty certain it is fine.

The snag is the SD1 starter is a pig to get at. And I'm getting too old to crawl under the car.

I've had Lucas starters where the pre-engage solenoid gets lazy - can something similar happen to this type? I've Googled but can't find a description of one.

richardpope50 · Post by **richardpope50** » Tue Mar 18, 2014 6:57 pm

Don't suppose it is as simple as greasing the shaft?

DaveEFI · Post by **DaveEFI** » Tue Mar 18, 2014 11:35 pm

richardpope50 wrote:Don't suppose it is as simple as greasing the shaft?

I'd be surprised as it happened quite soon after it was new. I'd expect that sort of thing only to need doing once in a blue moon.

I've Googled to try and find a drawing of it to see how it works - without success. I sort of assumed both the motor gearing and drive were common to other starters with just the adaptor plate a special.

conrod · Post by **conrod** » Sat May 17, 2014 10:11 am

Dave, the starter is actually engaging the ring gear. the problem is the sprag clutch is slipping. You will need to remove the starter and replace the clutch drive (the bit with the pinion on it) You can usually get these to start by holding the ignition in start for 10-20 seconds. the clutch drive gets so hot it locks up, then engine will spin over:)

Conrad

DaveEFI · Post by **DaveEFI** » Sat May 17, 2014 10:46 am

conrod wrote:Dave, the starter is actually engaging the ring gear. the problem is the sprag clutch is slipping. You will need to remove the starter and replace the clutch drive (the bit with the pinion on it) You can usually get these to start by holding the ignition in start for 10-20 seconds. the clutch drive gets so hot it locks up, then engine will spin over:)

Conrad

Interesting. I'd not tried that thinking I'd just be running the battery down for no reason.

But I'm confused - can a sprag clutch 'slip' unless broken? I can see it failing to engage, though. Can it be cleaned/lubricated? Where would I buy a spare?

conrod · Post by **conrod** » Sat May 17, 2014 5:28 pm

The clutch is only supposed to slip in one direction, the purpose of it is to prevent the starter from overspeeding (and flying apart) when the engine fires up. As you can imagine, the gearing of the ring gear to the pinion is typically around 12:1, when the engine fires up at say 1000rpm, if the starter is still engaged, then it would be turning 12000rpm. Now imagine if it is still engaged and when the engine fires, and it momentarily sees 3000 rpm, that would be 36000 rpm at the starter, causing a rather disastrous end to it all! The clutch drive allows slip in the direction of drive to prevent this starter overspeed condition.

Obviously the starter will only spin once the solenoid contacts are closed, and because the pinion is mechanically linked to the solenoid it means it is actually impossible for the starter to turn until pinion is engaged in the ring gear.

You cannot service the clutch drive, lubrication or solvents are the thing that usually cause them to fail:( Replacement is the only option. You have to try to identify the manufacturer of the starter. A lot of aftermarket manufacturers use something common as a base, such as Nippondenso. If you can take a good photo of the starter, I may be able to identify it for you.

BTW, later RV8 starters as fitted for Disco's and RR's are hi torque jobby's, much smaller and lighter than the old Lucas types, and more cranking power at less current draw. A cheap alternative to an aftermarket hi torque starter. Typically made by Bosch or Marelli.

Conrad

DaveEFI · Post by **DaveEFI** » Sat May 17, 2014 5:45 pm

Isn't a sprag clutch rather like a bicycle free wheel? In other words, can't slip as such (as a normal clutch might when worn) but simply fail to engage?

Take the point about cleaning it, though. It's quite possible it has got ATF on it - my GM box can leak when the car is parked on a hill.

I'm not sure if a later starter fits - the SD1 uses a different layout of starter to the RR due to space being tight.

But thanks very much for the info - I'll remove it shortly now the weather is better. It's an excellent anti-theft device, though.

conrod · Post by **conrod** » Sat May 17, 2014 8:54 pm

yep thats right about sprag clutch not slipping, it just works or "freewheels" in one direction. Next time you have a starter at hand, notice how you can push the pinion in one direction (and the shaft does not rotate) but not the other, that is the sprag clutch. It has rollers inside, similar to a roller bearing. The outside race has "ramps" which squeeze the rollers on the to inside, making it lock. They are sealed, but not very well. If you ever dismantle a starter to rebuild it, it is important not to wash this part, or let any lubricants near it, as ingress into the clutch part can render them useless.

If you do get stuck with a spinning starter, and must get the car started, try the trick I mentioned earlier about holding the key in the start position, it usually works!

I think the one on my LDV V8 might be useful, the solenoid is directly below the starter, and does not "hang out" as such. (it is a reduction drive type) I have a few late RR ones in the garage, I will check later and compare.

Conrad