Onan 4000 Microquiet not starting

Chinook wrote:
Just a "clicking" noise but won't turn over.

(that click is probably the sound of the starter motor running the starter Bendix
( gear on starter motor) into the gear on the flywheel on generator motor

This could be the sign of a low battery or bad cable connections with the resulting “stuck starter”.

I had a similar problem with my generator. I checked it before a trip to Alaska and all appeared to be fine. Used it a couple of times on the trip and then it wouldn't start. It got to the point that it wouldn't turn over and just made a click (klunk) that sounded as if the starter was jammed. After returning home, I found information this forum that explained that sometimes the piston in the engine could stop near the top of the compression stroke and the starter motor then could not turn the engine over.

The solution was to turn the engine over by hand so it was past the top of the compression stroke. I found that by putting a wrench on the nut on the flywheel, I could get the engine rotated past the compression stroke.

I also discovered that I was getting a big drop in the 12 volts as I tried to start the generator. As a test, I used jumper cables from my truck directly to the generator (negative to generator frame – positive to battery side of starter solenoid) and it started instantly. (after resolving the stuck starter by turning the engine over by hand) In my RV, the frame was used for the negative wire and the connections from the frame to the generator had corroded and although I could get a 12-volt measurement, the corroded connections would not allow enough current to pass to run the starter.

In addition to replacing the corroded connectors, I ran a heavy gauge copper wire from the battery ground to the starter ground. This solved my problems. As stated above, a large drop in voltage when trying to run the starter indicates a bad connection.

You might need to check ALL of your ground connections from the generator all the way back to the batteries.

A bad electrical connection increases the resistance in a circuit. Ohm’s Law states E=IR where E = voltage I = current and r = resistance

---- Since the battery voltage will not increase (it actually decreases with each attempted start), increased resistance causes a decrease in current. With a decrease in current, the starter motor produces less torque (turning effect) because the magnetic field produced in the starter is proportional to the current.

When the piston in the motor’s cylinder goes upward during the compression stroke the volume of the area from the top of the piston to the bottom of the cylinder head becomes less, According to Boyle's law, if you reduce the volume of a quantity of gas, the pressure will increase.

When the force of the gas pushing down on the piston (pressure) equals the torque of the starter the starter motor stops turning. Attempted restarting does nothing to change these forces and the starter motor in an attempt to turn, just runs the starter bendix into the flywheel producing the clicking sound.

By physically turning the motor past top dead center, by pulling on flywheel or placing a wrench on the flywheel nut, the piston starts on its downward stroke and the pressure becomes less so that the torque of the starter is adequate to rotate the motor.