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OnanMan
OnanMan, Generator Tech
Category: RV
Satisfied Customers: 255
Experience:  14 years in the Cummins/Onan distributor network, Level 3 certified in RV, Marine and industrial fie
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Onan..It starts fine and runs fine for about an hour..restart

Customer Question

I have an Onan Microlite 4000 in a 1996 Tiago Arrow. It starts fine and runs fine for about an hour to an hour and a half. Then it shuts off and will not restart. When I push the start button in the motor home it runs as long as I have the button pushed, but when I let go of the button it dies immediately. I have to wait hours in order to be able to run it again. Is there some sort of safety switch in the unit that shuts it off if it gets too hot? If so, what do I do to keep the switch from tripping? I should be able to run the generator without it shutting down on me.
Submitted: 5 years ago.
Category: RV
Expert:  OnanMan replied 5 years ago.
Hi I am Don. This originally sounded to me like the fuel pump or the fuel solenoid (on the bottom of the carb if equipped) is getting hot and then shutting down the gen. Then when it cools off it will restart. I do think you may now be experiencing 2 problems or if the gen will only run with the start switch pressed, that means the gen is not switching from the start mode to the run mode. This switching happens when the gen is producing electricity. This may be the original problem to begin with. Does the ges start switch have the ability to flash a code when this happens? Can I get the complete model number off the data tag that is on the gen?
Customer: replied 5 years ago.
Hi Don,

Sorry for the delay. I had to run out with a flashlight to locate it for you. The model # XXXXX XXXXX

The generator was just serviced for the seller by the Cummins dealership in Tampa, FL about two weeks ago because it wouldn't start consistently. They adjusted something and it starts fine. It runs for around an hour and then shuts off. It will not restart for many hours - as soon as I let go of the start button it dies. If I let it sit overnight, it will start again in the morning and then die after about an hour.

Does this info help?
Expert:  OnanMan replied 5 years ago.
Ok, this model had a problem with the oil pressure switch. The fix was to disable it because it is not really needed since the oil system is a "splash" type system, not an oil pump type. It may have already been disabled but I would like to know for sure. The wire runs under the engine to a spade like terminal. See if you can look under the engine part of the gen-set and find a wire that may be still connected, if so then disconnect it. If not,then find the wire on the control labeled J1-7 and then cut it off. Try that and let me know how it goes. If this doesn't help we can proceed from there. I am assuming the oil level is good?
Customer: replied 5 years ago.
I found a wire connected under the engine. I disconnected it and tried to start it. It wouldn't go into rev-up and died when I let off the start switch. I reconnected it and it went into rev-up, but then died when I let off the start switch. I did this two or three times with the wire disconnected and then reconnected to make sure. Every time the same thing as described above.

I don't know where the "control" you speak of is. I found bunches of wires that joined together in two bunches in plastic housings, but none of them was labeled J1-7. I found wires like P1-4 and stuff, but nothing in the J's. I came back and looked at a service diagram I found online. The only control mentioned is the control panel. Am I supposed to open the panel to find this wire?

The oil level was the first thing I checked. Filled to the max-line.
Expert:  OnanMan replied 5 years ago.
Ok if you disconnected the wire at the engine then that is all I need to know. It is not an oil pressure problem, You have an electrical output problem. Do you have an ohmeter that you can use to make another check?
Customer: replied 5 years ago.
No I don't have an ohmeter. Electrical output will keep the genset from running after an hour of running? When it runs, the power in the cabin for the a/c and other items is fine. Everything works fine until the generator just cuts out after about an hour, and then won't restart. That's why I asked if there was some sort of over-heating safety mechanism that has to reset after cool-down. The generator cranks and runs smooth as silk up to that point, and then it just craps out for hours without letting me restart. I notice the green panel door to the generator is pretty hot when I open it.
Expert:  OnanMan replied 5 years ago.
There is no overheating shut-down on this unit per se...meaning there is nothing that monitors temperature to shut it down if it gets too hot. That being said, if it gets too hot things can happen to shut it down because it got too hot, like the fuel pump. Now I need to ask you to please answer my questions if you would like for me to help. What is the status of the gen now? Is it hot? If not will it start? If it starts will it run for 5 minutes?
Customer: replied 5 years ago.
The generator isn't hot right now. Just warm. It starts and revs up as long as I'm holding the start button in. As soon as I let go, the generator immediately dies.
Expert:  OnanMan replied 5 years ago.
Ok good, I believe this was the original problem that has just become worse and now we are going to find out why. Do you have to plug the shore power cord into a plug to get gen power or do you have an auto switch?
Customer: replied 5 years ago.
I have to plug the shore power cord into a plug mounted on a box in the compartment where the cord is stored if I want to use the generator.
Expert:  OnanMan replied 5 years ago.
Very good!! This makes things easy, plug the shore power cord into that plug, and start the generator and keep the start switch pressed in, have someone go inside and see if you have gen power inside the coach, I usually go to the microwave but you decide what you know should be working, anything that you know works right away (some things have time delays).
Customer: replied 5 years ago.
I used the inside start switch which is located on a panel by the microwave. I held the switch in until the generator revved and smoothed, continued holding it in the start position while I opened the microwave door. The light did not come on in the microwave. I released the start and the generator died. Tried again to be sure, and the same thing happened. I'm not getting power in the cabin.
Expert:  OnanMan replied 5 years ago.

I am thinking that this was your original problem and now it just got to the point of total failure...If you would like for me to help then I would need you (or someone comfortable using) to use a voltmeter/ohmeter...it is getting late here (east coast USA!) I will wait for your to reply to see if I go to bed or we continue tonight, which I can if not too late..otherwise I work until around 6PM EST

Customer: replied 5 years ago.
We don't have a voltometer/ohmeter. I don't know how to use one anyway. I live way out in the boonies, so not a chance of finding someone close by that has one and can help out. Based on what you think the probable causes are for the problem you've deduced... about what can I expect to be charged fairly for repairs?
Expert:  OnanMan replied 5 years ago.
I think the brushes or slip rings (the slip rings are what the brushes ride on) might be worn out, how many hours are on the gen? If we can get a handyman to do the ohm check then I will know for sure. If this is the problem (and it is the most common problem), then the gen needs to be removed from the coach. Unfortunately the thing needs to be torn down to get to them! The brushes are behind the flywheel! Take it to a Cummins Distributor (not a Dealer)!! Very important! Because the distributor is bound to the Cummins SRT (Standard Repair Time) and let me tell you...we lose most every time..
Customer: replied 5 years ago.
The generator has 578 hours on the counter. I don't know if there is a cummins distributor in Polk County or not. I'll have to check. I can't leave the county - on probation.
Expert:  OnanMan replied 5 years ago.
I used to live in Polk county in Florida, are you in FLA? I know someone there that could help us out...
Customer: replied 5 years ago.
I'm in Lakeland, Fl. In Polk County.
Expert:  OnanMan replied 5 years ago.
I used to live in Mulberry..
Customer: replied 5 years ago.
I grew up in the Pipkin Road area of South Lakeland... not far from Mulberry. Now I live out in North Lakeland off of Rock Ridge Road.
Expert:  OnanMan replied 5 years ago.
ok, either way I can't help you without a mater of somekind....I am going to bed...we can figure this out another time if ya want..
Customer: replied 5 years ago.
Okay. Thanks for trying. I'm fixing to click accept after this reply. If you come up with any ideas of someone local that can work with me, my email isXXX@XXXXXX.XXX. Otherwise I guess I'm in the shits. Thanks again for trying. Goodnight.
Expert:  OnanMan replied 5 years ago.
Ok thanks. I really think it because the gen is not making electricity!! And that it was a problem that just got worse...
OnanMan, Generator Tech
Category: RV
Satisfied Customers: 255
Experience: 14 years in the Cummins/Onan distributor network, Level 3 certified in RV, Marine and industrial fie
OnanMan and 3 other RV Specialists are ready to help you
Expert:  OnanMan replied 5 years ago.
Thanks for the accept! There is a Cummins distributor in Tampa that can roll a service tech your way, don't know the number but sure bet you can find it on the net...

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