Onan Micro 4000 Generator Won't Start

Mich F wrote:
Glad you found your problem and posted what it was.

^^^^^^^ Same Here ^^^^^^

Thanks for posting back. ed s

txnese wrote:
There is a voltage drop on the solenoid output side as well as input side, but the battery itself stays at 12v. With a jumper box directly on the input side of the solenoid, the generator fires right up.

Proof positive that you have a bad connection somewhere between the battery and the input post on the solenoid.....or a bad cable.

I see that you found the problem.
Good work.

Glad you found your problem and posted what it was.

After tracing down the correct starter power wire. I found that it's mounted to the input side of the first solenoid, on top of the battery feed. So it doesn't actually go through the first solenoid (near the battery.) After inspecting the power wire and terminals, I came to the conclusion that it's good. With jumper cables directly from battery terminals to starter solenoid and generator itself (ground), it fires right up. I then removed just the power side of the cables and still good. I reinstalled the power cable and removed the jumper ground and no good. Bad ground right? Yep. I traced down the ground and found that there are 2 ground cables. 1 from house chassis to generator housing, and a second from the generator housing to the generator itself (control module had to be removed to see it). It's the second cable that was loose, so it showed me 12 volts when testing with voltmeter, but not enough to start it. Thank you everyone for your inputs.

The Second Solenoid is probably the FIRST solenoid, your House Battery Disconnect. It's got to be making up to "some degree" because most of your RV's 12-volt-DC stuff seems to be working. It could be damaged to where it won't pass enough current for the Genny, or (Again!) some Connection. Does it look sorta like This?
You can safely jump across the two LARGE terminals to eliminate the Disconnect as your problem.
Disconnects are Latching Relays, different than your Starter Relay. Latching relays stay "in state" once their control signal goes off. Your Start Relay has to have its control coil powered up, to continue cranking.
If you determine that you need a Disconnect Relay, know now that there are at least two different designs. Depends on the type of Control Switch. So, don't jump into an order. We can help figure out which type you need, but it's less than straightforward.

Before I decided to start beating on things. I just started back from scratch testing voltages at different points of connection. There is a voltage drop on the solenoid output side as well as input side, but the battery itself stays at 12v. With a jumper box directly on the input side of the solenoid, the generator fires right up. I'm trying to trace the power wire, but it looks like it's going into another solenoid, located near the battery. Am I crazy? Why would the power go through 2 solenoids. Either way, I should know something before end of the day.

Beating the Starter or any place you can get access to on the Engine part itself, won't get the crankshaft off of Dead Center.

Going straight to the Starter Cable, AND a good Ground on the Generator itself, with Automotive Jumper Cables, just might let a good starter muster up enough oomph to get a Topped or Bottomed piston moving.

But PLEASE!!! Only Bump it with all that battery power through heavy gauge jumper cables. A good starter motor won't be good long if it gets all that current without being able to spin!

txnese wrote:
Installed the new solenoid and same thing. 12v on the input and single digits voltage on the output side.

I think there is a flaw in your testing procedure.
That is theoretically impossible.....IF the solenoid is good.

For instance, you must make both measurements while the solenoid is engaged, while trying to start it.

Edit: Taken together, your comments about voltages and the solenoid clicking a lot might indicate that your engine is locked up.

If the plugs are easy to get to, running the starter with them out might tell you a lot (like if it is a hydraulic lock due to fuel in the cylinders).

I personally think you are down to a point where you NEED to take it to an Onan (Cummins) shop because the next things to do are either slightly dangerous or very expensive if you guess wrong.

txnese wrote:
I did apply 12 volts to the cable. I have to say, I think I hear an attempt to turn, but nothing loud. I also forgot to mention that the solenoid clicks a lot. On a known good generator, the solenoid does not click loud (I don't prime it, so the it takes 15-20 seconds to start. Just did it for testing.) Interesting on the TDC, I was think about beating it with a hammer tomorrow, but maybe I'll look for a way to spin it. I'll do searching tonight as well. Thanks.

One more fairly easy test to help pass judgment on the starter: How about pulling your car/pickup up close to the MH for a known good 12v source; remove the solenoid-to-starter cable (again) and connect it to the red on a set of jumper cables, then connect the blk to the generator body itself for ground (not the MH frame?) As j-d says....you should get a pretty good spark when you connect the ground (with 100 amps or so inrush current.) If "no crank" it should be either the rare TDC problem or a starter problem, I'd "think".

BTW- I just have a hard time envisioning a 4-volt drop across a new solenoid; i.e., measuring 12v on the inlet side and (at the same time) 8v on the outlet side while attempting to crank.

Sounds like you are "zeroing in" on this problem. Good luck.

I did apply 12 volts to the cable. I have to say, I think I hear an attempt to turn, but nothing loud. I also forgot to mention that the solenoid clicks a lot. On a known good generator, the solenoid does not click loud (I don't prime it, so the it takes 15-20 seconds to start. Just did it for testing.) Interesting on the TDC, I was think about beating it with a hammer tomorrow, but maybe I'll look for a way to spin it. I'll do searching tonight as well. Thanks.