ONAN Marquis Gold 7000 Gas

[Rich Biebel]

Dan that is exactly what needs to be done but isn’t by just about any builder of motor homes and trailers.

The newest vans with generators installed have sheet metal completely isolating the hot air exhaust side from the cool air inlet area.

It makes a huge difference on how well they run and last.

I see poor installs all the time.

[Mike Pearson]

I have an 8 K Onan diesel in my Toter. I live in Florida. When its hot I run a fan to blow the heat out from under the generator.

[FED 387]

looking back on the many questions and replies about Onan gens it seems not only Onan but probably many other gens have a lot of problems caused by OVERHEATING. If the gen had a lot of fresh air and wasn't jammed into a compartment WITHOUT sufficient clearance around it to allow the heat to escape this might cause the overheating--- I bet if you put a Onan gen on the ground in direct sunlit on a 100*+day it probably would run until it ran out of fuel with no problems whatsoever---Take that same gen cram it into a confined area with not much air circulation and its a recipe for disaster.
Perhaps a modification to the compartment and/or additional fans blowing LOTS OF COOLER AIR on the gen and to help get some cool air in there or out of there would lessen the chances for failure--MY 2 CENTS -- Mr Biebel care to comment please?--Fed 387

[1matcoman]

There's alot to be said in that regard, FED. And, I am sure Rich will agree.

We (the mobile tool industry) tried running Honda gen sets in our tool trucks a few years ago and experienced horrible results. Honda engineers ultimately totally agreed that the problems were caused by us putting them in those small compartments where they were subject to too much heat.

While we tax the Onan products by running them so many hours a week in such heat, they are still the best thing going for anyone, or anything, requiring mobile power.

[Sean Marconette]

I went through all the same overheating issues with my Onan a few years ago. The main problem is the way the LQ conversion factory installed the generator with very limited ventilation. The intake air and exhaust air not being separated and ducted apart to eliminate recirculation of the heated air. This eventually causes the board to overheat and either shutdown or fail. Another racer informed me last year that Onan makes riser kits to elevate the generator, and has a divider and can pull intake through the front. This solved their overheating issue. It's unfortunate that the trailer manufacturers that install the generators do not follow the recommended clearances for ventilation provided by the generator manufacturers.

Without help from Rich I was ready to give up on a generator that had very little run time and failed every race we went to. I have ducted the exhaust air to discharge to the opposite side of the trailer from the intake air, and we have a box fan that also runs to ventilate the generator compartment.

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https://mart.cummins.com/imagelibrar...es/0058349.pdf

[Rich Biebel]

I have serviced and repaired the 7kw gas units since they redesigned them. Had a long list of mobile dog groomers that came to me regularly. They have vans and the generators were mounted in various places over the years by basically one builder. They build a number of different vehicles and the latest is a Dodge Ram long van with the generator in the back on the floor in a compartment with a door and completely enclosed. The cool air intake is below the floor and the hot air exhaust area is completely isolated with a screw together sheet metal cover. I just serviced the one I point to all the time. 3755 hrs and the young lady takes great care of it. Oil changes and full service as recommended by Onan. It’s 5 years old and like new. Does not get road debris in it and runs as good as one could with that many hours. Serviced another long time customer last week. Older style van with Gen in rear side compartment and on support legs as all of those are. 7750 hours and I’ve repaired it a few times. New cyl heads at 3 or 4 thousand hours. She’s probably my longest dog groomer van customer.
Installs are terrible on many vehicles. The builders never read the install guidelines. Food trucks and sign trucks ....and I’ve seen racer trailers just as bad or worse.

Heat kills these machines, they are AIR cooled !!

Ask Lee and Brian Valentine about their Onan that would shut down last year at MG Div. Race. A new LQ trailer with Gen install by the trailer builder. A fan blowing on the unit kept it going. I gave Lee some suggestions and they made some changes and it’s been ok.

I need to add that no Onan air cooled machine has any specific hi temp shutdown sensor.
They just shutdown from either control board overheating or a vapor lock/ carb issue. The heat also kills the plastic floats in the carb. and you cannot buy any parts for that carb. I replace them often anymore. A Complete carb is all you can get.

[FED 387]

Rich--- does any gasoline WITH ETHANOL affect or deteriorate the floats ??? I know on some of my older personal yard stuff it STRONGLY recommends against using gasolines with ethanol or very small amounts of ethanol but preferably NO ethanol ---whats your take on this??? FED 387

[Rich Biebel]

The newer machines in the last few years have had odd carburetor problems that I never saw before.

Random issues with stalling. When it gets real bad gas just pours out the carb.

Float appears darker but does not have fuel inside it. It gets heavy and sinks and floods.

Last week I spent a good 2 hours on a machine that would run for a few minutes and just shut off. I chased it changing various components and a new carb fixed it. They have a solenoid on them to shut fuel flow off thru the main jet. The solenoid was causing issues with feedback to the control board.

I always say there is nothing one of these machines can do that I haven't seen......that was a completely new one and the carb issues have been also hard to diagnose.

I lost a customer over that one probably....A girl had repeated issues and no matter what it never failed for me when I tested the machine.

Ethanol creates a gunk different than fuel used to create if it sat. Used to be gummy varnish in reg fuel. Ethanol leaves a greenish, yellow sugary like substance. Both will cause big problems......

My son was/is a motorcycle person since forever. He used an ultrasonic cleaner for carbs...…..I never have seen or used one myself for carbs.

On generators I replace them most of the time.....waste to much time trying to clean an old one and most of the time it takes numerous tries to get it working decent....

[Greg Barsamian]

Originally Posted by FED 387

Rich--- does any gasoline WITH ETHANOL affect or deteriorate the floats ??? I know on some of my older personal yard stuff it STRONGLY recommends against using gasolines with ethanol or very small amounts of ethanol but preferably NO ethanol ---whats your take on this??? FED 387

On my Honda Generator, I've had success using Av-Gas!
(110 low leaded fuel, cheaper than SEF)

[340Cuda]

I live in Tulsa and the availability of what is called E0 is quite good for 87 and I use it in my generator, lawn tractor and other small engines.

E0 91 is available but not as easy to find as the 87. We have not had 93 in any form in this area for a long time.

The E0 is often advertised as "Real Gas".