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 > Onan Micro 4000 Generator Won't Start

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txnese

Pearland

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Posted: 07/10/18 03:09pm Link  |  Quote  |  Print  |  Notify Moderator

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?

Mich F

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Posted: 07/10/18 03:32pm Link  |  Quote  |  Print  |  Notify Moderator

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


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txnese

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Posted: 07/10/18 05:08pm Link  |  Quote  |  Print  |  Notify Moderator

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?

j-d

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Posted: 07/10/18 07:10pm Link  |  Quote  |  Print  |  Notify Moderator

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.

* This post was edited 07/10/18 08:16pm by j-d *


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txnese

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Posted: 07/10/18 09:00pm Link  |  Quote  |  Print  |  Notify Moderator

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.

youracman

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Posted: 07/10/18 11:04pm Link  |  Quote  |  Print  |  Notify Moderator

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.


Ed Sievers, Denver, CO
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Sam Spade

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Posted: 07/11/18 06:05am Link  |  Quote  |  Print  |  Notify Moderator

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.

* This post was edited 07/11/18 06:11am by Sam Spade *


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j-d

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Posted: 07/11/18 07:21am Link  |  Quote  |  Print  |  Notify Moderator

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

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Posted: 07/11/18 08:06am Link  |  Quote  |  Print  |  Notify Moderator

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.

j-d

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Posted: 07/11/18 08:26am Link  |  Quote  |  Print  |  Notify Moderator

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? [image]
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.

* This post was edited 07/11/18 08:33am by j-d *

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