Onan Micro 4000 Generator Won't Start

txnese wrote:
...took the “solenoid to starter” cable off the solenoid and applied 12 volts. Nothing. Shouldn’t the starter try to spin?

You applied +12VDC direct to the cable powering the starter. If both ends of the cable are good (the terminals and the connection to the starter motor), then it should try to crank...IF... the -12VDC (the ground) is good, all the way back to the battery.

When you did that, did you get a "healthy spark" indicating there was a goodly amount of current being drawn? Some of your comments about Voltage Drop indicate that the Starter is drawing Current but not Cranking the Genny. No Cranky, Correct?

Just had An Epiphany: It hasn't happened to me, but I've heard of 4KY's stopping with their ONE PISTON at Exactly Top Dead or Bottom Dead Center. When that happens, the Crankshaft that the Starter is trying to turn, has pretty much Zero Leverage against the friction of the Piston Rings in the Cylinder Bore.

The fix was finding a spot to poke a socket wrench into the genny, get the right size socket on the flywheel nut, and just budge the crankshaft. You aren't trying to "crank it." Just getting it "off center." Your starter might just then roll it over. Hold the Start/Stop switch in "Stop" before you try to crank it. Will run the fuel pump and get the carb primed with gas. Increase your chances of it actually starting.

There are OP's here who can tell you the socket size and how to snake it in there.

I did. I also just took the “solenoid to starter” cable off the solenoid and applied 12 volts. Nothing. Shouldn’t ithe starter try to spin?

Maybe I missed it, but have you tried starting your generator while your MH engine is running ?

Installed the new solenoid and same thing. 12v on the input and single digits voltage on the output side. Tested at battery itself and doesn't drop much at all. Too hard to tell if there's a ground cable to the starter itself. Can I assume the starter is grounded by being bolted to generator? Has anyone had a bad starter on their generator?

txnese wrote:
when I reconnect the cable to the starter, input side has 12 volts, output side has 8 volts. So either starter is bad and drawing too many amps or solenoid is bad.

IF....both of those measurements were made with the start button pushed, then the contacts in the solenoid are burnt. When the solenoid is closed, the voltage should be the same on both sides.....regardless of whatever else is happening.

txnese wrote:
I have a voltmeter on the battery and voltage stays about 12v during starter.

If that really means "during the time the starter is trying to run", then it indicates that there is a bad connection between the battery and starter. That might include the contacts in the solenoid.

The voltage at the starter should be within a couple of tenths of what it is at the battery.

Yup.........your diagnosis sounds "right on". Really hope it turns out to be a bad solenoid. I had to drop the whole unit on mine to replace a bad/weak magneto..........not fun, but doable. Whole thing weighs about 175 lbs.

Look fwd to your "got it fixed" post.

When I removed the cable from the solenoid to the starter, I get 12 volts on both sides of the solenoid with the start button pushed. when I reconnect the cable to the starter, input side has 12 volts, output side has 8 volts. So either starter is bad and drawing too many amps or solenoid is bad.

I've ordered a solenoid and it should be here Monday. Will keep everyone posted.

txnese- re: " I tested the output side of the solenoid and get 12v with starter cable disconnected, with starter connected I get 8 volts"

I assume you get the 8 volts while pressing the starter button. Please also let us know what voltage the other (power input) lug on the Onan starter solenoid reads while holding the start button down. If the 12 volts you measured at that lug was "open circuit" it does not guarantee you have a good copper path all the way to the battery; but a measurement under load tells a lot more.

Just data, FYI: My Onan service manual states that the minimum voltage allowable at the starter itself is 10 vdc. Of course "more is better"..... a lot better.

Also just some "real world" data: I actually pulled the plug wire and measured the starter current on my 4K Onan Microquiet a couple of years ago. It was 57 amps steady state. As DrewE mentioned, the inrush current is probably at least 100 amps.

Good luck with the fix.....keep us posted; we're all learnin'

ed s Currently: Denver, CO Formerly: Alvin, TX

Battery was left to charge overnight. Tested fine with voltmeter, I also took it out to O'Reilly and have them tested the batteries. I have a voltmeter on the battery and voltage stays about 12v during starter. Tested on the input side of the starter solenoid and voltage is above 12v, this should show cable connection between battery terminal and solenoid is good. I tested the output side of the solenoid and get 12v with starter cable disconnected, with starter connected I get 8 volts. Bad starter? In the meantime, I'm double checking grounding cables.