Bench run an Onan P-Series

[boovuc 1,090]

Years ago when I got my spare Onan, I ran it on my work bench from instructions Duke sent me but I can't find them. 

I want to run the P220 now that I did all this clean-up, adjustments and a few replacement parts. (Was going to do a compression test on it but didn't have enough jumper cables to just crank it tonight).

 

Could I run a low current wire from the + terminal of the battery to the coil + then run my ground on the big jumper cables to the block and then use the + big jumper cable to touch the starter + to start it?      

 

Just don't want to fry the ignition module, coil, voltage regulator, myself, garage, the regional grid, etc. I have all the shrouds off except the flywheel cover at this point. (I'll have to make sure the regulator is properly grounded before I start). I have no solenoid. This would be just a battery, jumper cable and some low current wire.

 

Thanks in Advance!

[ericj 1,576]

run a wire to the + side of coil and hook the the big jumper wire to the battery then take a second small wire and just touch it to the flat terminal on the starter, were the blue wire hooks on from the wiring harness. if you want to do compression test just don't hook up the wire to the coil . keep the jumper wire on the starter though, with the wiring harness on so that the voltage regulator always see's 12 volts or other wise you will burn or short out your rr. good luck and let us know how the compression test goes and how it runs

 

 

 

 

 

eric j

[boovuc 1,090]

OK, let me see if I follow you Eric.

 

1. Hook a jumper wire from the + of the battery to the + of the coil.

2. Have my jumper cables hooked to: negative to the block and the positive to the +lug of the starter?

 

Here is where I'm more fuzzy than usual. Do I have all the wires from the engine harness connected as well as my voltage regulator hooked up?

If so, then where and with what am I jumping the small flat terminal on the starter. (Ground to the flat terminal)??

 

And you thought I had some sense about this!!!!!

[boovuc 1,090]

March Madness at camp now thru Sunday! Going to walk away from that Onan for a few daze! 

Eric, All: If you can break it down better on wire location?

 

Thanks!

[ericj 1,576]

sorry i didn't see this last night and get back to you sooner. yea hook all of the wires up just like you would to install the motor on the tractor. your voltage regulator needs to see 12 volts to avoid shorting out. then pull the blue wire off the starter flat terminal connector, then take a jumper wire and go from flat terminal to the positive battery terminal on the starter. this should engage the starter and with 12 volts to the coil it should start. and of course fuel in the carb. good luck. they tell you to take a compression test warm but i like to take it cold. if it's good cold then it has to be good warm right ? and i found out you also need to make sure the carb butter fly and choke is open  

 

 

 

 

 

eric j 

Edited March 21, 2015 by ericj

[Save Old Iron 1,563]

I have never had any issues with regulators attempting to short out if no load is put on the output. I have dissected, repaired and tested several "Onan style" regs and never had one react adversely to no load.

 

If you do fear reg issues, just disconnect one of the stator lines into the reg and leave it at that. No stator line connected - no reg powered up.

 

 

[pacer 3,160]

I think I have "bench" started every horse that I've had (usually just a quick bolt down in the frame to cut down on jumping around on the bench ) Seems like when I buy a horse its so far from just starting with a turn of the switch til I wouldnt know how to react if one did! Anyway, I hook it up as simply as possible using jumpers - 12V to the coil and jump to the starter til it goes. Actually I never really gave a thought to the reg ... have never had a problem yet.

[ericj 1,576]

I've had at least one rr go bad that i thought was because i blew the fuse and didn't know it. i always figured that's why the warning was on the the tractor at the battery not to run with out battery hooked up or charging system damage would occur but if S.O.I. says it won't hurt,   but i think i'll play it safe and put 12 volts to the rr can't hurt right

 

 

 

 

eric j

[pacer 3,160]

I will clarify my 'bench' starting an engine - the 6 or 8 that I have done that with were all older models, and all Kohlers, newest was 81, and that is likely more of a factor in later years/models...

Edited March 22, 2015 by pacer

[Save Old Iron 1,563]

double post - see below

Edited March 22, 2015 by Save Old Iron

[Save Old Iron 1,563]

The over whelming majority of regulators I have investigated have died from poor solder joints from the manufacturer - ultimately opened up by vibration on the tractor - or from corrosion of the copper traces and terminals attached to the circuit boards.

 

The RR below shows many poor solder joints. The failure of this RR was due to the resistor (blue banded object in photo) pulling right out of the solder joint. This resistor is the "calibration" of the RR unit to regulate at 13.8 volts. Without this reference, the RR could not function. Simply re-soldering the connection brought this RR back to life.

 

P.S. also note in the image below, the two wire terminal tabs are soldered and riveted together, therefore are electrically the same connection. This image further confirms the myth if these two terminals show a short, the RR is bad, Measuring two terminals shorted is not a confirmation the RR is bad.

Edited March 22, 2015 by Save Old Iron

[Save Old Iron 1,563]

another RR view

[Save Old Iron 1,563]

another bit of food for thought - if there was a possibility of the RR destroying itself without a load attached, you would think we would see a dead RR with every instance of corroded wiring to the ignition switch, disconnecting the RR from the 12 volt battery. I am open to discussion on this but I cannot see any electrical property of the RR that would allow itself to "burn out" without a load attached.

 

The sticker stating do not run without a battery attached is on several models of tractors. I 'm wondering if the sticker appeared when indicator boards appeared on later models.

Edited March 22, 2015 by Save Old Iron

[pacer 3,160]

"you would think we would see a dead RR with every instance of corroded wiring to the ignition switch,"

 

Boy oh boy, now theres food for thought! Connections on our tractors are notoriously corroded, especially in the charging circuit.

 

By the way Old Iron, my thanks for your faithful, knowledgeable responses to our - many - electrical issues on our horses....

[Theroundhousernr 589]

  I think more of the issue with running without a battery is having the battery leads just dangling inside the hood. Damage to the regulator could be from the positive lead grounding on the frame and burning things out. I agree with SOI on this one also. The regulator has nothing inside that would build up a charge that needs to be discharged. Like an ignition coil for instance.

 

  However, since the RR keeps a constance Voltage in comparison to battery voltage. What is going on with the logic of the circuit when it has no reference from the battery?

[boovuc 1,090]

Thanks for all the replies. Back from March Madness Camp Weekend. Need to detox my system and rebuild some brain cells then I'll go out and........(1) do a compression test. (2) If I get 90 or better PSI in each cyl, I'll fire it up and run it a bit.

Not sure if I'll get 90 in that rear cyl or not. Hoping I do and I won't need another spare because I don't need a parts motor! 

Thanks Again Guys!

[boovuc 1,090]

As you may have read in 'Engines", I cranked it and got a whopping 32 PSI on my compression test. I tried firing it but it only sputtered except for a 10 second run. Battery died so I hooked up my charger to my donor battery but while it was hooked up to the motor. Also, the charger has a booster option!

Guess what?

My coil was hotter than the hubs of Hell! I hope that is all that may have fried. Nothing else was warm except the front cylinder. (NOT THE REAR).

I hope nothing passed to the stater since this is a duel cylinder paperweight, I need all the good things off of it I can save! Yes! I'm an idiot but it took years to perfect it!

Edited March 26, 2015 by boovuc

[WNYPCRepair 1,875]

Thanks, these instructions came in handy.
 

[Save Old Iron 1,563]

The START function on higher powered battery chargers will put 20+ volts into the electrical system.

Coils get hot,

tachometers get fried





and the ignition module on 520's can be stressed / damaged.

Cranking a battery dead, then being impatient and over-volting the battery to rush recharge can cost you - big time!

Edited July 17, 2015 by Save Old Iron