Onan 5500 Marquis dies in hot weather

[joedaddy805]

I have a Onan 5500 that works great in my driveway or at the beach. But once I go up in the mountains and it's 80+ the gen wants to die till it cools down. I've heard that if you run it without the cover it will cause it to overheat. I don't understand the concept of that cause it will hold the heat in more. If I take the cover off it has a lot of heat come out. So I leave the cover off till it cools down then put it back on then it runs till it gets hot again. I've ran it a few times without the cover and it seems to run a lil longer than usual. I'm lost on what its issue is since it runs perfect when the temp's are low. I'm sure everything like the pump and filter are fine cause it runs great when in cool weather. I was thinking of installing a fan underneath it to pull some heat away from it but not sure if that will help. Any info would be gratefully appreciated.

[IdahoSRT10]

Plenty of threads in this.....do you have a solid door in front of the generators intake?

[Rocky Larson]

What do you have the elevation dial set to?

[joedaddy805]

Its a sea lvl when I'm home and at around 4k when I'm up in the mountains.

Yes its all solid door. I leave the trailer door open when its running.

[IdahoSRT10]

Originally Posted by joedaddy805

Its a sea lvl when I'm home and at around 4k when I'm up in the mountains.

Yes its all solid door. I leave the trailer door open when its running.

I've found my gas Onan gen runs cooler/better at sea level setting. I believe the higher alt. settings cause a 'lean condition' contributing to overheating.

Most solid doors help trap the heat in the compartment. The gen. has a intake fan that sucks air through it exiting out near the exhaust. I installed a door vent w/ shroud to force cold air in the compartment. Re-routing and insulating the exhaust away from under the gen. also helps.

[joedaddy805]

I've tried running it at the lvl i'm at and also sea lvl. Either way it does the same thing. I was thinking of cutting a whole in the door and putting mesh wire but I dont think it would help any since the front of my gen has a solid door. I guess it pulls the cold air from the bottom not sure. I'll try and figure out how to post a pic of my set up.

[joedaddy805]

Exhaust out the side.

Bottom of gen.

[joedaddy805]

Originally Posted by IdahoSRT10

I've found my gas Onan gen runs cooler/better at sea level setting. I believe the higher alt. settings cause a 'lean condition' contributing to overheating.

Most solid doors help trap the heat in the compartment. The gen. has a intake fan that sucks air through it exiting out near the exhaust. I installed a door vent w/ shroud to force cold air in the compartment. Re-routing and insulating the exhaust away from under the gen. also helps.

I like your setup. I wish i had the same setup as yours cause I would of built the same thing you have. I was thinking of buying another cover for the gen so i could cut out a piece and put a fan on it to push or pull air whichever one would work the best. I dont know if installing 2 radiator fans on the bottom would help with bringing in forced air to help with the cooling.

[IdahoSRT10]

Looks like your undercarriage is sealed. Maybe a complete new vented door with a built-in low profile electric rad. fan will help to get some air movement. Just a thought but fuel vapor lock can't be ruled out (insulated the fuel line near the gen.) Does the fuel pump click a lot before it dies?

[joedaddy805]

Originally Posted by IdahoSRT10

Looks like your undercarriage is sealed. Maybe a complete new vented door with a built-in low profile electric rad. fan will help to get some air movement. Just a thought but fuel vapor lock can't be ruled out (insulated the fuel line near the gen.) Does the fuel pump click a lot before it dies?

I was thinking of doing something to help with air flow. Don't know if I should put 2 fans on the bottom to get the air moving over the gen and just leave the door open. I have insulated the fuel line close to the gen but i think I'll be doing that next cause either way it won't hurt it. I've heard of people saying the fuel pump could be a issue cause it gets hot and doesn't work good enough. Not to sure about that one. I could try a new fuel pump since they are cheap but it doesn't seem like a real easy job to do since its buried in there pretty good. Something i don't want to do unless I really have to.

[joedaddy805]

No more thoughts?

[roadster27]

check the air door by the air cleaner , there is a winter/summer leaver to apply more heat to the carb for cooler temperatures , mine is at the back of my Georgie Boy 34 ft , as far as 4000 ft , mine runs fine and my house is at the bottom of the mountain at 4000 ft , unit comes from Ontario , California 3 years ago , check fuel pressure at the carb with a gauge , should be over 4 psi

[Lt Dan]

Originally Posted by joedaddy805

I have a Onan 5500 that works great in my driveway or at the beach. But once I go up in the mountains and it's 80+ the gen wants to die till it cools down. I've heard that if you run it without the cover it will cause it to overheat. I don't understand the concept of that cause it will hold the heat in more. If I take the cover off it has a lot of heat come out. So I leave the cover off till it cools down then put it back on then it runs till it gets hot again. I've ran it a few times without the cover and it seems to run a lil longer than usual. I'm lost on what its issue is since it runs perfect when the temp's are low. I'm sure everything like the pump and filter are fine cause it runs great when in cool weather. I was thinking of installing a fan underneath it to pull some heat away from it but not sure if that will help. Any info would be gratefully appreciated.

I had the same problem with my Onan 5500. It would run fine in cool weather, but in the heat it would run 30-45 minutes and shut down with no trouble code displayed. I replaced the fuel pump and it ran fine on our last trip before I traded it in. I never got a chance to give it a workout in hot weather though. The pumps are available on Amazon. Find your model number and search for Airtex and the model number. All of the OEM fuel pumps are made by Airtex. I paid about $45 for mine last year.

By the way, unless yours has a vent in the door from the factory, you should not add one. The 5500 is designed to have air flow through the generator coils to keep them cool. If you leave the door off or cut a vent, you interrupt the normal air flow and it can cause it to overheat.

[Starsekr]

Originally Posted by IdahoSRT10

Looks like your undercarriage is sealed. Maybe a complete new vented door with a built-in low profile electric rad. fan will help to get some air movement. Just a thought but fuel vapor lock can't be ruled out (insulated the fuel line near the gen.) Does the fuel pump click a lot before it dies?

Fuel pump/vapor lock was my first thought. try putting wet rags around filter and pump/lines, give it a min or two and see if it restarts.