DB880 - Lucas M45G Starter

The starting motor fited to 880 Diesel engines is a four pole four brush earth return machine with series parallel connected field coils. It is a Lucas M45G type, with an integral solenoid-operated pre-engaged drive assembly. You can click on the images here to see a larger view of the picture. Removal is quite straight forward, with only 3 bolts holding it on to the flywheel housing, and two electrical connections to the solenoid. One mystery that I have yet to figure out is the fact that this tractor is wired for negative ground, which is not what the book says it should be (should be a positive ground system). But that was how it was when I got it, and for the time being, that is how it will stay until I can get a good wiring diagram.

Over the winter, I noticed that on occassions, the starter wouldn't turn over the engine, but just klunk when I hit the starter button. Thinking it was just a battery problem from sitting out in the weather for long periods of time, I would slap a battery charger on the tractor and wait about a half hour to have it start right up. Then one day this spring, it just stopped working. All I would get was the dreaded klunk, and nothing I did seemed to change that situation. After exhausting everything I could think of (clean cables, jump start from truck, etc...), I yanked the starter to see what was going on. Of course, the first thing I thought was that the solenoid contacts were dirty, so that was the first thing I cleaned up. Then, since I already had it off the tractor and partially disassembled, I thought I would give the brushes a once over for good measure. Well, to my suprise, one of the brush springs turned out to be broken.

Great!! I thought, beliving that this was the source of all my problems. A quick spring replacement and I'd be on my way again. Well, let me tell you, trying to find parts for a Lucas starter around here is no easy chore. I finally found one spring that was just about identical at a local alternator/starter repair shop here in town, and the guy didn't even charge me for it as he had yanked it from somewhere in a pile of old dead starters. The next day I had the starter reassembled and back on the tractor, only to hear the dreaded klunk once more. I was not happy at all.

With the starter pulled and disassembled again, I went over every part of it looking for some sign of trouble. After much head scratching, probing and poking, I decided to throw a meter on it to see if that would turn up anything. Sure enough, it turned out that the field coil was shorted to the frame. Now I really wasn't happy. I've rebuilt starters before, and I know what a nightmare just trying to get the field coils out can be. They must torque those screws down with an impact wrench set at maximum. That was it for my I'll fix it if it kills me attitude, and off I went to the same place that I got the spring from. After about 30 starter catalogs and cross reference books, it was determined that a suitable replacement could not be found. So a rebuild was in order, and I had it back in a couple of days all cleaned up and freshly painted (black!).

With a grin on my face, I slapped the starter in, hooked everything up, pushed the starter button, and.. you guessed it, the dreaded klunk which was the same sound as my head hitting the bonnet. Once again, off it came and back to the bench. A quick bench test told me that the solenoid was engaging, but wasn't making contact with the starter circuit, as I could jumper the solenoid contacts and have it spin over. Not wanting to take anything apart now that someone else had done the work, back to the shop it went to let them deal with it. All I wanted was a starter that worked when I returned to pick it up, and that is exactly what I got.. finally.

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