Onan Genset blowing fuse

lemortede · August 13, 2015, 10:34 AM

I have a microlite KV 2.8 generator.
Its runs great but has recently taken to blowing one of the fuses below the start switch on the gen set.
There are 2 fuses and a circuit breaker on the gen set start switch. As you are looking at it its the fuse to the right.
I believe in the repair manuals they call it F1 but I am not 100% sure.
Its a 120 v 5 amp fuse.
The repair manual says "check fuse, if open locate and correct cause of overload. replace fuse"
Any ideas what I should be looking for on the overload or where to look for the problem?

Bnova · August 13, 2015, 11:31 AM

Looking at the manual, it appears that if f2 opens, one of the things that won't happen is the fuel pump won't get power during engine crank up. If f1 is open, the fuel pump will not be powered after engine crank up.

Presumably your gen won't start. Or if it does, then it does not continue to run. But it sounds like these two fuses are protecting the generators internal wire harness. A first guess would be fuel pump wiring or the pump itself, but looking at the wire diagram, it could be a number or areas.

Knowing whether or not it will start and continue to run will help pin down the problem a little.

lemortede · August 13, 2015, 12:01 PM

Once the fuse blows nothing happens.
It doesn't turn over at all.
If I replace the fuse it turns over and starts.
I had this fuse blow before and replaced it and didnt have an issue after.
Right now I am looking at either a ground issue, or disconnecting the remote start switch.

jeno · August 13, 2015, 01:50 PM

are you using a slow blow fuse?

Bnova · August 13, 2015, 02:03 PM

Ok, found a wire diagram that is legible, and the remote sw and the onboard sw are both wired into the negative side of everything, so if their wiring had a short it would not cause the F1 to blow.

If you can get to diode cr2 and disconnect it, you can disconnect the pos cable from the battery and ring out the wires from the fuse holder, there should be open circuit reading to ground on the ohmmeter in both directions. If not, then you gotta isolate even further, but at that point if you're getting into the harness you might easily spot the problem anyway, chafed insulation somewhere most likely.

And I mentioned fuel pump wiring in my earlier post, that was before I saw the wire diagram, and the could in turn cause this problem, but it's a pretty long shot that that's it.

lemortede · August 13, 2015, 02:06 PM

I went out and bought some fuses a while ago, dont know if they are slow blow. I will check. would that make a huge difference?

Bnova · August 13, 2015, 02:15 PM

I don't think so, it doesn't mention "slow blow" in the manual where they are described. My parts manual is at home right now so I can't look it up.

lemortede · August 13, 2015, 02:19 PM

What I heave read is if you are blowing the fast blow fuse you will more than likely blow the slow blow.

lemortede · August 13, 2015, 04:12 PM

So when this happens the MH is not plugged into the gen socket. Once I plugged it in it seemed fine. I am going to add a ground strap.

Bnova · August 13, 2015, 04:18 PM

Interesting.

lemortede · August 13, 2015, 08:06 PM

So used my disconnect switch and turned it back on and the fuse blew somewhere in that process.

Bnova · August 13, 2015, 09:19 PM

Not sure what you mean by that, what does the disconnect sw disconnect? And when you say "turned it back on" are you saying you started the gen again and it blew the fuse on engine crank?

DaveVA78Chieftain · August 13, 2015, 09:24 PM

The only things I can think of:
The fuel pump drawing to much current.
Resistor R2 shorted resulting in to high a voltage to fuel pump (increasing current flow through fuel pump)
Choke coil pulling to much current.
Run time meter (on remote) pulling to much current

lemortede · August 13, 2015, 10:52 PM

So I got home from work, bought a fresh box of fuses and found the following:
With a new fuse I was able to start the generator, run it for a while then turn it off. With in a minute I can then start it again, run it for a while, but once I turn it off a second time the fuse blows.
If I put in a new fuse I can repeat the process.
I dont have a run meter so I can eliminate that.
I think that fuel pump or choke coil makes the most sense.
How do i test resister R2?

Bnova · August 14, 2015, 09:07 AM

So you're thinking the fuse blows when you shut it down?

But what about the post where you said something about it blowing the fuse when using disconnect sw? Sounds like it blew on start up, but need more explanation. And what is the disconnect sw?

Regardless, K1 (start sol), K2 (start disconn rly), K4 (gov arm sol) and K5 (power to fuel pump) are all connected to F1. On shutdown K4 & K5 get energized from the negative side and K2 de-energizes as gen a/c volts drop below 70 volts. K1 doesn't do anything, it is de-energize after start up, it is the start solenoid, but it has a connection to F1 so when K2 de-energizes on shutdown it applies power from F1 to K1 so that it is ready again for another start-up.

Sorry about all the detail, and obviously it is going to help to have the wire diagram in hand but these are the things that happen on shutdown and I would be looking at the wiring to those components first and if no discrepancies are found then I'd go after the components themselves.

lemortede · August 14, 2015, 12:43 PM

So I just spent the morning looking things over and happened to see sparks coming from the front of...well, im not sure what it is.
I uploaded a video to Youtube. It will be done uploading around 11:15 AM MST.
http://youtu.be/SD-e91w42us

M & J · August 14, 2015, 12:59 PM

I see the sparks but cant tell exactly where we are looking. I see what looks like the governor arm moving, and if so is it the carb we're looking at? If so, the only electrical around it is the electric choke wire.

Bnova · August 14, 2015, 01:14 PM

Looks like you found a definite problem, K4 Gov arm solenoid. Is it shutting down on its own in the vid or are you initiating a shutdown?

When you initiate a shutdown, that solenoid is supposed to push the Gov arm and that closes the throttle assisting engine shutdown.

It appears that the solenoid is being energized, hence the sparks. Which would lead me to think that you are initiating a shutdown with the switch. And looks like you'll need a new K4 solenoid.

If the sparking shown in the vid is happening on its own without you initiating a shutdown, then you have more problems. Hopefully it is just a toasted solenoid causing the problem.

lemortede · August 14, 2015, 03:30 PM

No, when that is happening I am not initiating a shut down.
I have pulled that part and now the generator is running smooth and not blowing the fuse.
How critical is that mechanism? am I going to hurt it running with out it for a bit until I can get a new one.
I wonder if the relay that it connects to is bad or having issues.

Bnova · August 14, 2015, 05:16 PM

Quote from: lemortede on August 14, 2015, 03:30 PM
No, when that is happening I am not initiating a shut down.
I have pulled that part and now the generator is running smooth and not blowing the fuse.
How critical is that mechanism? am I going to hurt it running with out it for a bit until I can get a new one.
I wonder if the relay that it connects to is bad or having issues.

I would say it all depends on how well it shuts down without it, might be ok, because ignition and fuel pump are cut at the same time during shutdown. This K4 solenoid closes the throttle on shutdown.

Is it shutting down normal like now without the solenoid? If so, I'm sure you could continue to use it. I would get a new one very soon though if it were me.

I would start with the K4 solenoid and after replacing it, just monitor the operation. The relay that it's in parallel with is K5 and that one provides power to the fuel pump. So unless you're having other problems after the new K4 is installed I'd call it good.

lemortede · August 14, 2015, 08:21 PM

It starts runs and stops with no problems so I will give it a crack for the short term until I can get a new one.
BTW. Thanks for being a sounding board everyone, especially Bnova.
This was a new problem for me and I really didnt have anyone else to bounce things off.

Bnova · August 14, 2015, 10:57 PM

Nice you were able to figure it out, didn't take you very long either. We're all just guessing here, throwing out ideas, you're the one that has to do all the work. Have a beer and celebrate

lemortede · August 16, 2015, 12:03 PM

So we went out and tested things. The generator ran great once I adjusted the altitude mixture.
the part that looks like I need to replace is
307âˆ'2659 1 Solenoid, Throttle Closing
(Includes Nut and Washer)
(K4) (KV)

Thanks again for the help.