Quantum 5.5 electric start help

[hikerboy]

I recently picked up a craigslist $25 1995 Snapper RP21550E electric start self propelled mower. Filthy and neglected. Briggs 5.5 Quantum engine, starts easily by pull rope, runs great after installing new carb, air cleaner primer backing plate, and spark plug. I checked all the connections, installed a new battery, and no crank.....I removed the starter, found that it was hard to turn by hand. Got it freed up, then applied 12 volts to it, voila, it spins. Noisy but spins. Reinstalled, put new interlock switch on, still no crank. Swapped ignition switch with a known good one, still no crank. Battery is charged. I don't know what else to check other than I'm guessing there is something wrong with the starter. $125 to get a new one, ouch! Hoping someone has some insight. Thank you!

 

[Scrubcadet10]

i would check that you're getting 12volts at the starter.
does it make any noise? does the bendix gear pop up and try to engage the flywheel?

 

[hikerboy]

12 volts at the starter when key is turned to start. So obviously my issue is in the starter. Weird that it will spin on the workbench when 12 volts are applied to it, but not when installed on mower. I grounded it on the bench, maybe I have a grounding issue?

 

[Scrubcadet10]

12 volts at the starter when key is turned to start. So obviously my issue is in the starter. Weird that it will spin on the workbench when 12 volts are applied to it, but not when installed on mower. I grounded it on the bench, maybe I have a grounding issue?

Run a jumper wire from the - on the battery to the starter/good clean ground metal, and try it.

 

[hikerboy]

Bingo. Starter spins with negative jumper wire grounded to frame. Any guess where to chase the bad ground? Thank you!

 

[upupandaway]

Bingo. Starter spins with negative jumper wire grounded to frame. Any guess where to chase the bad ground? Thank you!

Bolts to the engine are your ground. I would check the safety switch. Have the wifey hold the key and dead man bar to crank and check that voltage make it to the safety relay and if the safety switch does close the circuit. Then see if voltage goes out of the safety switch to the motor. That is pretty much the only othe part of the circuit unless u have bad wire itself.

 

[Scrubcadet10]

let me look up the model of the mower again and see if i can come up with a wiring diagram.....

 

[Scrubcadet10]

evidently this is what the battery/starter harness is,
i would start by tracing where the black neg wire grounds too, taking it loose and cleaning it up with a wire brush etc and tighten it back up.

 

[Scrubcadet10]

https://www.ereplacementparts.com/snapper-rp21550e-90s-55hp-steel-deck-recycling-electric-start-series-parts-c-207777_207876_211134.html

 

[hikerboy]

Thank you! Tomorrow I will remove the starter, clean the bolts and bolt holes, and the starter bracket. Will also look at the wires again, I did clean/wire brush the terminals and the connectors as much as I could. Safety interlock switch seems to be working fine.