How to prevent generator vapor lock

[kmb1966]

I have a Onan Gold 7000 generator. Runs fine normally, but sometimes when traveling in hot weather it develops vapor lock. When it happens, it has been when temperatures outside are above 97/98. We hate to travel when it is that hot, but sometimes crossing Texas in June/July, it's unavoidable. When it's that hot it is also a time that you really need the a/c working well, and if the generator develops vapor lock, then no a/c and it's a miserable situation. I'd like some ideas on how to avoid this situation for this upcoming summer. Thanks.

Onan is installed in a Itasca Suncruiser Motorhome

[hotpepperkid]

MMMMM think we used to put a clothes pin on the fuel line

[Dutch_12078]

The almost no cost fix would be to move the fuel pump from the generator to as close to the fuel tank as practical. Other than the labor, all that's needed is some wire and maybe a couple of screws. Pushing the fuel to the engine is much less prone to vapor lock than pulling.

[Kayteg1]

I wonder if that is vapor lock as well.
Not being familiar with the generator in topic, but most of generators do have gravity-feed carburetors.
Having vapor lock in those is not possible.
On the other hand carburetors have nasty tendency to flood the engine when fuel is not shut-off and they are exposed to movements aka hauling them on RV.
I am pretty religious about shutting fuel off to my Honda and it always starts on 1st pull in hot weather, having it tested at 122F.
It failed to start on me years ago at -20F, but that was different story.

[maddoget]

I would replace the fuel pump. The heat causes pumps that are weak to fail. When my Onan 5000 did what you are describing, I replaced the oil sensor, spark plugs, air filter, fuel filter, and fuel line from the tank to the fuel pump. And after all of those parts the generator stop did the same thing. Purchased a new fuel pump and shazam, the generator ran like it was brand new.

[ernie1]

I agree these problems are heat related. I have an Onan 2800 in my PleasureWay class b van and find it runs flawlessly if the outside ambient temperatures are not really hot like maybe 95 degrees Fahrenheit or below. Once the temperatures climb and the generator has run for awhile, it will shut off abruptly but can be started up again and run for a short while like 10 minutes and shut off again. After it has shut off and not run, I'll get a very strong smell of gasoline for about an hour or so. I think the carburetor is so hot that it is percolating the gasoline out of the bowl. When running the generator in these hot conditions I find that if I remove the black metal cover on the front and run without it in place, it happily runs along without stopping nor any percolating of gasoline due heat soaking. Maybe some sort of cooling fan can be installed? But where?

[cgmartine]

I purchased a new fuel filter and fuel pump, and I am in the process of moving them outside the generator compartment, where they will not be affected by generator heat. Mine will be in a metal box I bought from Home Depot. I am also replacing all rubber fuel hoses all the way to the tank and making sure they are nowhere near a heat source. Some others have gone as far as fabricating a louver and venting system on the door of their motorhome, since it all seems to be heat related

[msmith1_wa]

I have had what I think is the same problem. I added the fuel pump below close to the tank and connected it to the original pump wireing. It has only been a couple of weeks since I did this, but so far so good.Fuel pump

[dkreuzen]

What is the diagnostic code reported? It should point to what the problem is.

[alfredmay]

Cooling the fuel will also help. A cooler if mounted in a stream of air that is not heated by the engine, AC, tires, etc may be the solution. You can buy one for around $60.

http://www.ebay.com/bhp/fuel-cooler

[kmb1966]

cgmartine wrote:
Did the original poster resolve this issue? I have been keeping a close eye on this issue and it appears that this issue is more prevalent that one would imagine. Possibly all heat related. One suggestion I have heard is to move the fuel pump out and away from the generator enclosure. Do we have an update on this?

I am the original poster. I have not found a solution to this problem. I purchased a roll of 'cool tape' at the auto parts store. I wrapped the fuel line all the way from the tank to the fuel filter and then from the fuel filter to the carburetor. This summer coming across Texas, it was even hotter than it was on the previous trip. This time the generator stayed running better to approx. 110 outside, whereas before it was stopping at around 100 degrees. But I am not sure if the cool tape helped, or it was other variable factors.
Someone had mentioned that using no ethanol blend fuel would help. We did try to find no ethanol fuel on our summer trip, but it is not practical to find no ethanol blend fuel on a trip. So, in summary, we have not found a solution. In our case, we were thankful that our DASH A/C still works well. It's a shame really that when you need your generator the most for a/c, in hot weather, the gas generator has problems. It is either overheating, or vapor lock, not sure which.

[MEXICOWANDERER]

Just as a note- the higher the fuel pump sits from the fuel the greater the pressure drop and closer to vapor point the fuel gets. Heat makes fuel even less dense. One diagnostic would be to lessen the total lift of the fuel (fuller tank of fuel). If. the problem persists, a pressure gauge should test for pressure on the fuel out port of the pump.
A weak pump cannot supply fuel to a desired height. This is where a disconnected fuel pump volume test an be misleading so avoid doing it as step 1. Only a pressure check will reveal a weak pump. Then do the bulk flow test.

Way back "in the day" chassis engines used mechanical pumps. With a long rig and a steep hill the total lift increased beyond the ability of the pump. Electric fuel booster pump sales, thrived.

Pressure and fuel delivery specs need to be referenced to give fuel pump testing any value.

[cgmartine]

Did the original poster resolve this issue? I have been keeping a close eye on this issue and it appears that this issue is more prevalent that one would imagine. Possibly all heat related. One suggestion I have heard is to move the fuel pump out and away from the generator enclosure. Do we have an update on this?

[wa8yxm]

There are several conditions mistaken for "Vapor Lock" Classic vapor lock is when the gasoline in the fuel pump vaporises so the pump is pushing gas. not liquid, since gas compresses easily it can not supply the engine with enough fuel.

This should not happen once it has started as the flow of FRESH gasoline from the tank will keep it pumping liquid.

One solution is to Choke the thing breifly on start up but.. Well, to be honest this should not be necessary on the ONAN since they use a fuel pump that is .. Resistant to Vapor Lock.

So are you sure it's vapor lock?

[time2roll]

More ventilation for the fuel pump and the fuel line going to the pump.
If this is a recent problem it could be a weak fuel pump.