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Tap on starter and ...

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it works again. Went to start the engine this afternoon on my 9020 Pow'rMax (Is 9020 and Pow'rMax redundant?) and it wouldn't turn over. The amp meter showed a large draw but nothing. Then I tapped on the starter as a last resort and it worked. Solenoid or some other issue?

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HubbardRA
If tapping worked, then this usually means that there is a dead pole on the commutator inside the starter. The tapping will make it contact the one be side it and it will start turning. Bad thing is that they will almost always stop on the dead pole. Another thing that it could be is worn bushings in the starter. This will allow the armature to be off center and not make enough torque to start turning. Sometimes when you tap on them, they will start turning if the tapping has moved the armature close enough to center. In my experience for tapping to work in these situations, the key needs to be held in the start position while tapping, so that the power can flow when things line up.

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Guest
Am I correct by looking at where the starter is located that I'll have to raise or remove the engine to service it?

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Al
Hi, There are 2 probablilities here. 1. The starter. 2 The tractor. I am sorry, but I was wiped out last night and will try to address this tonite. lets start with the starter. The starter consists of 2 components, the solenoid and the starter motor. These are called solenoid shift starters, the solenoid pulls the shift lever on the drive and mechanically pulls the drive into the ring gear on the engine. When the plunger in the solenoid has the drive engaged it pushes on a "button" in the back of the solenoid. This button is attached to a copper disc that then contacts the two large terminals on the back of the solenoid. One has the battery cable and the other the heavy lead from the starter motor. This puts battery voltage on the motor which under normal conditions causes the motor to rotate. Normally if the bushings are bad, the motor will still turn, but the armature will drag on the field pole pieces and the motor will have low torque and maybe turn slowly and growl. Normally a starter has 4 brushes. 2 from the field coil and 2 to ground. This energizes 2 armature windings 1 on each side adjacent to each field pole piece. In most of these Onan starters, there 3 brushes, and one brush serves for both grounds. Now the details of solenoid action. The solenoid has 2 windings in it a pull in winding and a hold in winding. The hold in winding normally draws from 8 to 13 amps and is connected from the small (energize) terminal and ground. The pull in winding normally draws about twice the current of the hold in winding. Ad the two and normally one sees 30 to 40 amps on pull in. If 12 volts is applied to the terminal and the hold in winding is the only one in the circuit, it will NOT pull the plunger in, but might make it rattle a little until the slack is out of the shift lever linkage. The Pull in winding is connected to the same terminal as the hold in winding. The other end instead of going to ground connects to the big terminal that powers the starter motor. When the key goes to start, the current path is from the small terminal through the hold coil to ground (one magnetic field) and also through the hold winding to the starter motor. Since for practical purposes the starter at stall is like a direct short to ground for the pull in winding. (the second and much stronger magnetic field) At this instant 2 things happen. ! the solenoid plunger starts to move, and the current through the winding to the starter motor starts to magnetize the fields and armature in the starter motor and the starter motor will start to turn slowly. As the Plunger pulls the drive in there is a spring behind the drive gear so if it hits the ring gear tooth instead of sliging between the plunger goes on back and compresses the spring pushing the drive gear against the ring gear. The current through the pull in winding starts to move the armature and the spring causes the gear to mesh as the armature turns a little bit. This provides a "Soft Start" and takes a lot of shock load off the starter drive train. As soon as the plunger gets completely in and pushes the disk against the contacts, the battery is connected directly to the starter motor and the motor turns with full torque. Note that another thing has happened. The pull in winding Now has 12 volts on the little terminal and 12 volts on the end at the starter motor. The result is it no longer has any current flowing through it and the hold in winding holds the plunger in until the start switch is released. The current on the little terminal drops from over 30 amps to about 10 amps. Now a couple of scenarios. If the brushes are worn badly and are not making there is no current path for the pull in winding. Tapping the starter may cause the brushes to move enough to just touch. If this is the case, continuing use can cause arcing that blows a bar out of the commutator and you now have a junk armature. Second situation if the armature has fractured connections from the windings to the commutator the armature may provide an OPEN circuit when the defective bar is contacting the brushes. Same result, no pull in winding current path. (NOTE: NEVER! NEVER! NEVER! POUND ON THE PERMANANT MAGNET STARTERS LIKE THE SMALL BRIGGS, TECUMSEH, AND KOHLER STARTERS. THEY HAVE POWDERED IRON MAGNETS GLUED IN THE CASE. POUNDING CRACKS THEM AND THE LITTLE PIECES STICK TO THE ARMATURE AND WON'T LET IT TURN. THEN THE ARMATURE MELTS DOWN. NO FIXING, NEW STARTER) These are the main issues in the starter. Now number 2 the unit. When these Indak ignition switches and safety switches are used in equipment that has an engine with a solenoid actuated starter, these switches see the nearly 40 amps required to pull in these solenoids. They are way over their reliable capabilities. As they age the internal contacts degrade and wires get a strand broken here and there. As a result, sometimes they work and sometimes they don't. If you have a unit that starts OK and when hot don't or you have to hit the key 4 times to get the starter to kick in it is probably the unit. Dirty battery cables can cause this also. We ofen see voltage drops down to 7 or seven volts at the energize terminals, this is not enough. We make a relay kit sells for 29.95 with complete instructions to fix this. Then instead of the key switch having to handle all that current a 40 amp relay does it. We have put these on dozens of units and it has fixed every one that has a good starter on it. One customer had an Onan powered skidloader that he put 3 rebuilt starters on in 6 months. Sometimes it would start, other times not or he would have to hit it 3 or 4 times. Has fixed it for 4 years. Sorry this is so long, but it is hard to explain with less. Al Eden

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JP
Yeah to what Al said! More fuel on the fire........ Make sure it is properly grounded. Sounds redundant, there's a few of us here that have increased the size of our 'bald spot' due to this! The grease/oil film on the engine or starter mounting spots or poor cables may contribute. Wire size + age + connections. The 'double selenoid' (relay as Al mentions) works wonders!

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Guest
On all three of my Power Max’s I've added a ground cable from the frame to the engine. No more starter problems for me!

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Al
Hi, You are absolutely correct, clean connections and good grounds are absolutely essential and in my comments I was assuming that as a matter of good practice these items had been attended to or checked out. You guys are right on Step 1. Clean cables and ground connections. Al Eden

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