Onan quits when hot

[FW5000DRIVER]

What about installing an after market fan down below? Or even adding oil additives to keep the temperature down. NASCAR uses such additives to keep engine temperatures down.

My BGE Genset is a four stroke and I assume yours is also. So maybe this would help while you are high temperature areas. http://www.stp.com/faqs/general/

[clyon51]

No doubt it is well over 120 degrees since they are going down left and right this summer. Years ago many mfgs put vents on the genny bay door to pull the air from the outside rather than underneath. I suppose they quit doing that because it didn't look nice....but doing so was a bad idea.

It would be nice if genny mfgs would put shrouds on the air inlet narrowing to a 3" pipe. Then the RV mfg or owner could add sufficent flexable pipe to an area where the air is coolest.

I believe the RV mfg should completely close off the genny bay. Then have something like a stove exaust vent on the bay door. Then all cooling and combustion air would have to come from the side of the coach where there is much less heat.

[cb1000rider]

So here's my attempted solution:
1) Replace the 13-year old fuel pump. Onan pumps are made by Airtex. The Onan Marquis 5500 takes an Airtex E11010. Drop in replacement, connectors are exactly the same. Save about 75% off of Onan retail.

2) Wrap that fuel pump in thermaflect Cloth. I have no idea if this will work or not, but my theory is that the pump is cooled by fuel and that the outside air temperature isn't helping.

3) replace the fuel line from the pump to the carb. OVer that line, I installed automotive heater hose, just slid it over. The way the fuel line is run, I couldn't cover it 100%, but I think every bit will help.

4) Moved to 30W oil, per Onan manual for highest heat range. Made sure not to over-fill.

Won't know if this works until we take it on the road when it's 105+ out.

[clyon51]

Cb1000rider -

I hope this works for you and may if its a vapor lock problem. If it's a high temp oil shut down problem, it won't do anything. Working with air cooled engines all my life, there is only 2 ways to keep them from overheating.

Sufficient ambient temperature air flowing over/through the cooling fins on the cylinders. When this is questionable or at it's limits, then an added oil cooler is needed.

Same principal in a transmission. It can't disapate enough heat on it's own, so a fluid cooler is added.

Keeping oil temps within specs prevents high temp shut downs.

[CLIFFTALL]

As I posted above , my 36 code turned out to be a fuel pump. I had Cummins do the work. They put a flow meter on the gas line and showed me the difference between old and new pump. It was almost double. I also changed both fuel filters and air filter. I too was in those high temps out west. If I hadn't seen this flow meter I might have thought it was from the heat. I traveled for about two more weeks in that heat without problem. I am now ( thankfully ) in much cooler temps in upstate NY.

[clyon51]

Had a similar problem with a Generac. I removed the fuel line and activated the pump. Seemed to be pumpimg OK to me. Since it was 12 years old and I had a new one with me, I swaped it out. Problem solved. This wasn't in a high heat situation, but it sure could have been.

[KWitzki]

Originally Posted by w6pea

I have a 2005 Fleetwood Jamboree 26Q. While we were in Las Vegas a couple of months ago, my Onan Micro 4ky Gen-Set did the same thing. I went and had to replace the carburetor today, (for a different reason) anyway the service tech said that when I was parked and using the Gen- Set be it hot or cold outside he recommended opening the door to the Gen- Set for better air circulation.

Also he said that say I was going to travel in my RV, that he always recommended when you are traveling that to exercise the Gen Set, start it and then turn the Air Conditioner on high and let it run. Go figure..

I was told the same thing about running the Gen. when traveling. Add some carb cleaner to the tank and that helps keep the carb clean.
Also Truckers Rule! Twenty odd years behind the wheel.

[cb1000rider]

Originally Posted by clyon51

Cb1000rider -

I hope this works for you and may if its a vapor lock problem. If it's a high temp oil shut down problem, it won't do anything. Working with air cooled engines all my life, there is only 2 ways to keep them from overheating.

Yes, I'm guessing as it's not easy for me to get it to the conditions that overheat. I'm largely guessing based on the rpm changes just before it dies, but again, I'm still guessing...

We're going to pull all the covers and clean the fins just to be sure.

In terms of oil cooling, do you know of an "easy" way to access the oil feed path on the Onan. I agree if it's not vapor lock, I'm going to have to do something more significant to address the total heat issue... I haven't seen an air-cooled Onan with an oil cooler yet.

[clyon51]

Originally Posted by cb1000rider

In terms of oil cooling, do you know of an "easy" way to access the oil feed path on the Onan. I agree if it's not vapor lock, I'm going to have to do something more significant to address the total heat issue... I haven't seen an air-cooled Onan with an oil cooler yet.

I haven't had an Onan in awhile and would have to look at it. It's certainly going to have an outbound and inbound oil galley to and from the oil filter and that's usually where the oil temp switch is. That's where one would have to incorporate an outbound line to the filter -> to cooler -> back to engine.

I've never seen any portable air cooled generator with an oil cooler. This is because they are designed to operate in open air, or at least where they can get sufficient cooling air. Sorta like encasing your CB1000's engine in an enclosed box, it's going to overheat.

MH mfgs, at least some, do not use their noodles when placing an air cooled engine in their MHs

[cb1000rider]

Interesting.. I found another thread where Thor is having to vent generator doors.. Course these are new RVs and they apparently ignored Onan's installation manual in terms of clearance and location of the air intake:

http://www.irv2.com/forums/f121/ace-...-125555-8.html

I replaced the fuel pump on ours and insulated the fuel lines. This should help if it was vapor locking, but won't help if it is over-heating and tripping an internal sensor... Course, we won't know until it's 105 and we're on the road.

[Leave Weds]

I too am having a code 36 shutdown with our Marquis 5500. I too think it is heat related but here's the deal: We are at the drag strip parked in the 'black asphalt' pit area....above 100 deg. all day. Even when it cools in the evening it shuts off! I've read in this forum that it might help to put louvers in the front pannel or even remove it. But the onan mech said not to remove it. It has to be in place for the air to circulate properly. So far I have a remote fuel pump, regulator (set at 2.5 psi) and filter. These are all located in a compartment next to the gen so they can't overheat. Where is this 'air intake' located? I've seen a picture in my installation manual but it just points to the front panel. Help us please:-Onan can't.

[clyon51]

I'm pretty sure if you look on the left side of the enclosure, you will see the air intake louvers. The exaust goes out the bottom. I agree with that tech, do not do anything to that enclosure.

The problem is not enough cool air, caused by high outside temps and parked on black top. However, these gennys are designed to operate in high temps. The problem in RVs is how the mfgr installed them and where. Barring a bad temp sensor, debris in genny blocking air flow, or some other defect in the system, the air the genny is using (being pulled from under the coach) is just too warm to cool properly.

Coaches with no louvers on the bay door to get cooler air from the side rather than from under the coach, experience this problem. If you are still in this situation, I would open the bay door when running the genny and see if that corrects the problem. If it doesn't, then I would suspect you have other issues.

[Busyteach]

We had this same problem with a 5500 in our Fleetwood. It happened with air temps at 106 degrees. I got the same code mentioned and really could not find the problem so I just attributed it to vapor lock. We traded the coach off this spring so hopefully we won't experience that again.

[cb1000rider]

My theory is that we were getting vapor locked. This fall replaced the fuel pump and insulated the fuel lines. Hopefully that takes care of it..
On an electronically controlled Onan, it'll likely detect temperature and shut it down.