Onan Generator was looked over by Cummins dealer about a month ago during my purchase process. I used the generator successfully on a weekend trip about 10 days ago and it ran for about 7 hours keeping both a/c's and other items working nicely and noticed a constant temp according to my gauge of approx. 190. Used the generator again this past Saturday for approximate 3 hours while working inside the coach and needed power and a/c because of the heat. Again, everything worked fine and a constant temp throughout of 190. Left for an overnight trip yesterday morning and about an hour into the trip, (on highway) the generator stopped. I looked down at the gauges and noticed temp gauge reading 220. I assume the gauge is relatively accurate, even after shut down. I hope that there is a safety switch on the generator that automatically shuts down the generator during an overheat situation and/or loss of oil pressure. I allowed the unit to cool down over several hours, and attempted to re-start the generator to see if it would start. Everything sounded normal as it quickly turned over and started to run briefly (seconds) until I let up on the start switch and it stopped running. Is there a relay or re-set button somewhere that may prevent it from re-starting? I lifted the hatch and looked around but it was getting dark and has limited time, light and tools to get a good look. Belt is still intact based upon what I can see. Any thoughts or suggestions are appreciated.

You've got a 1990 Regency. The generator should be diesel.

Perhaps there is a low coolant shutdown or low oil shutdown attached to the generator. Have you checked the fluid levels yet?

Is this the first time you've used the generator while driving down the road? Maybe the Barth is creating an airpocket void while underway??? Seems unlikely though and it wouldn't explain why it doesn't start now unless it does have a low coolant shutdown...

My 1993 Regency with the Kohler diesel generator experienced similar symptoms which I traced to a weak fuel booster pump. There is a small electric fuel pump located on the inlet side of the engine fuel pump (which is mechanical). This provides between 6 and 9 psi pressure to draw fuel and lift it to the internal pump. They are easy to check - take off the fuel line at the outlet and crank the generator start - if no fuel comes out it is bad. These are available from most auto parts stores for around $50. Overheating is protected by the high temp sensor which shuts the engine down. Check the water flow at the radiator cap after you get it running, flush the system with a good cleaner, change the thermostat and gasket and then operate for and hour or so to confirm its operation. Not much else could cause this.

The generator is a diesel. I have used it on the road before, with various wind directions etc. I have noticed that the generator temp gauge will typically read around 190. I have also used it while sitting still, as I did last Saturday, and everything was fine, and the temp gauge read consistently around 190 or slightly higher over 3 hours. I do not currently have a way to test the fluid level on the generator radiator. It was checked as recently as 3 weeks ago (besides the day I bought it) when had oil changed and all fluids checked.

Virtually all liquid-cooled gensets have a high temp cutoff (as well as a low oil cutout).

You could have a blockage of the radiator or low coolant. There has to be a way for you to check the coolant level.

Worst-case would be a failed coolant pump, although the symptoms don't indicate that.

Interesting. I opened the genie radiator cap and it is filled with fluid. No obvious leaks or problems. Hit the start button again, and I notice the plunger/rod moving out and it seems to start and as soon as I let go of the start button button, I notice this plunger/rod return and the generator shuts off. I then hold the start button with one hand and the plunger/rod with the other and the generator will start and run fine. Unfortunately, I forgot to put an electric load on it, but while I had it running, I wanted to see if would get to normal operating temp and then what. I let it run for about 5 minutes or more while holding the plunger/rod and it ran and sounded fine. The water temp started to climb and as it got to about 180, it started struggling to run and shut off within a few seconds. I tired to restart, and it did restart, but only for about 30 seconds and it shut off again. Any thoughts? more than one problem?

Were you holding the solenoid plunger rod in the whole time? When it ran to 180 then shut off?

yes, I was holding the plunger rod in the entire time.

I'm not sure what model Onan you have... But, here is one type - most of this is cross compatible anyway. This photo may not properly represent your Onan, but it'll be close.



See the item in the lower left labeled... Fault Reset Breaker - Have you tried to reset it yet?

No? Well, what are you waiting for?

Each sensor is faulted to ground... What that means is, if you take off the wire the sensor will not trip the fault.

Lets say that your high coolant temp sensor is defective - remove the wire to the sensor, reset the fault breaker and attempt to start. If you hook that wire back up and the engine shuts off - then that sensor is defective. BTW: The high coolant temp switch grounds out at 222°F

The exception is the device labeled "Control Power Latch" what this does is supply a grounded path to a relay - that switch would need to have the wires run together if that is defective.

Anything you disconnect or run together is only being done to test!!! if you leave something bypassed then all you've done is open yourself up to a potential catastrophic failure in the future.

Now - if this doesn't make sense - call a professional - if it does, I'll keep feeding you more test procedures - I'm pretty sure that the first thing is going to work anyway.

Now the question is... What caused the overheating condition in the first place?

Maybe a piece of paper or plastic got stuck on the generator's radiator. The engine shuts off because it really did overheat, the obstruction falls off the radiator and you're left scratching your head trying to figure out what happened. Don't laugh... this scenario plays out every once in awhile.

Your scenario is truly baffling to me. Your diesel can only shut down in two ways a) no fuel and b) no air. I suppose there is c) catastrophic seizing of the engine too.

So, if you were holding open the fuel solenoid plunger and it shut down anyway, how could that be?

Have you checked the condition of the air cleaner? Did a squirrel take up residence in the intake? Have you checked the fuel filter? Have you sampled the fuel for contamination/water? Are the injectors plugged?

Perhaps it is not an overheating condition.

The fact that the engine wants to turn itself off by way of the solenoid does indicate there is something that the electronic fail-safe circuits find out of congruence.

The plunger is the run/stop solinoid. These usually have two internal coils. The first is the pick and the second is the hold.

Ground to the solenoid is ok as the pick is working because it pulls in when you depress the start. The hold circuit is not. As Bill pointed out, you have overheat sensor and a low oil pressure switch in line with the hold circuit. On my Yanmar, 12vdc is routed thru the temp and oil switches to a start relay and then to the hold.

My first guess is a bad connection in the circuit and if not a bad run/start solenoid.

quote:

My first guess is a bad connection in the circuit and if not a bad run/start solenoid.

Gary, he said it shut off even while manually holding the plunger in the on position. There is more going on here than a defective fuel solenoid.

The first time he had this problem was when it overheated. The engine shutdown is set up so that you need to manually reset it each time it trips.

Engine overheat - manually reset the shutdown switch - see if it start up and report back here.

I find it odd that it shut down with him holding the plunger too - but he stated that it took 5 minutes that time.

Let's start off with what we know.

He stated it shut off when the engine temp hit 220°F - the tech sheet for Onan shows that it will trip the manual reset breaker out at 222°F. He never said that he reset the breaker so let's try this first.

Re-set button located and pushed in (set). Generator starts right up - ran no load for about 5 minutes and temp climbed to what I have seen as normal = 190. Initiate load of one roof a/c for another 5 minutes or so and temp stays constant. Add more load with second a/c and have maintained constant temp at 190 for about 20 minutes now. Although I am under cover, outside temp is mid-80's and both a/c's working pushing cold air so I know I have a decent load on unit. Since I found and re-attached two broken wires the oil pressure gauge is also working now and reads 1/2 way between 40-60 psi. All seems "normal" to me. Maybe something got sucked up onto radiator? It is located on passenger side near front bumper and the day it overheated we had strong breeze crossing from the drivers side. Have checked as much as I can and see no blockage, leaks, damaged hosing etc.

About 65 minutes run time with load and temp gauge reading just about 195 (?). Coach sitting still under cover with mid-80's outside temp.