Thoughts on Starter Drive Wear and Engagement By John Jervelund The relationship between the starter solenoid, shift lever, & drive, and ring gear .. is both complex and L simple. The simple part is that in response to the pull of the solenoid, the shift lever pivots on an axis, pushing the drive into engagement with the ring gear, the sole- noid contacts close, and the starter starts to spin. The complex part is that the timing of this sequence is absolutely critical. If the starter is spinning before the drive is fully engaged, or the retraction of the drive from the ring gear is delayed, both the drive and the ring gear will be dam- aged. The question is, what would cause either of these conditions to exist? Solenoid-activated starters can be divided into two groups, fixed and adjustable timing. They share some things and are very different in others. Here are a few causes to think about. Ring gear wear—While this cause gets a lot of play and blame, in actual fact, I don’t think it is as big a factor as it’s made out to be. If the ring gear were badly worn, it would be possible for the drive to skip on the edge of a tooth and increase its rpm substantially before contacting the next tooth. If this were the case, it would most likely be accom- panied by quite a bit of noise—enough that the owner would be investigating. The most probable result of this con- dition is a broken DE housing, similar to what Delco experienced with their Lester 6449 starter (although their problem was caused by a defective crank positioning sensor). Alternately, if there were a burr on the teeth, the drive might not be able to penetrate the ring gear, but more likely would be held by the spin of the ring gear, causing a delayed retraction. Wear on or a twist in the spline that the drive rides on, could cause the drive to be delayed engaging the ring gear, or retarded on release, as could a sticky material on that spline. The wear or twist would have to be fairly slight or the drive would hang up completely, either engaged or disengaged. If the problem was a sticky material on the shaft, it would most likely occur more often in cold weather. A bent shift lever will take the starter out of time the instant it happens. It is worth comparing the lever you want to salvage with a new one, to be sure it isn’t bent. It is also worth marking each lever as to which side was in or out and marking all of them in the same fashion. This will enable you to spot a reversed lever and possibly a bent one. Some shift levers are made from a bent piece of steel shaped like a “U.” It is important to know which way the “U” faces —toward or away from the sole- noid. On some of the Denso/Deere direct drive starters, if the lever is reversed, the starter will work as long as the engine starts! Should the engine fail to start, the solenoid will not disengage and will keep the engine cranking until the cables are taken off or the batteries go flat. In either case, the starter will be destroyed. On the Denso/Deere starters, the flat of the “U” must face toward the solenoid. Shift lever wear—On fixed timing starters, the shift lever is the timing mechanism. If there is wear on the but- tons, the drive will not be pushed forward properly and the solenoid contacts can close before the drive is properly posi- tioned in the ring gear. Wear can occur on both sides of the buttons, but the most wear usually occurs on the side that is against the drive while it is being pulled out of engagement. This is because the drive collar is up against the buttons in a metal to metal contact for the time it takes the armature to stop spinning. This makes a case for changing the brake washer every time, instead of try- ing to salvage it. If the drive is spinning for 1/10th second longer than it is sup- posed to, it will rotate an extra 60 times. I have been told that the pinion on a Delco starter is spinning at between 30,000 and 35,000 rpm just after the key is released. Wear on the retracting side should cause prolonged engagement, not pre- mature spinning. But when someone has removed the lever and re-installed it backwards the effect is opposite. Even if the lever is re-installed the same way it came out, with worn buttons the drive will remain engaged for longer than what was intended and the clutches will be worn prematurely (see previous para- graph). The wear on a shift lever button should never exceed 10 percent on the pull-out side. I don’t think anyone has established a wear maximum for the push-in side; if they had, it would be much less than 10 percent. Timing on the adjustable style of starter is, in some ways, even more problematic. Some starter manufactur- ers use shims, some an eccentric pivot pin, and others an adjustable rod on the plunger assembly. However it is done, it is exact, not something to be guessed at. On Delco heavy duty starters, the timing is not exact, only + or – 1/32 inch (.031 inch). In Lucas starters it is measured in thousandths of an inch