89 EMERALD 1 GENERATOR KEEPS RUNNING OUT OF GAS

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89 allegro

89 allegro

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Joined
Jun 4, 2018
Posts
95
Location
middle georgia
hi again everyone ,well my 89 allegro has a generator about 20 ft from the tank,its a onan emerald 1 generator,sometimes this thing seems to run for hours with no problem and other times it runs 20 min and cuts off.i have a clear inline filter right at the generator and i can lay there and watch the filter get lower and lower till it quits.i replaced it with a new facet one a few years back and it does the same thing my original one did ,so not sure what the problem is.i have ran all new fuel line from tank to generator ,so its  not the line,.i called the company and they told me the fuel pump needed to be put at the rear by the tank for it to push the fuel instead of pulling the fuel, but i really dont understand that since they are made on the side of the generator from onan.so has anyone else had this problem and if so how did you solve it or did you end up putting your pump at the back by the tank like they are telling me to do? i dont use the generator alot but i like it to work when i do need it without dieing every 20 minutes or less and it starts back up as soon as the fuel gets back to it.once again ,i can watch the filter go dry ,so its not a safety switch or anything like that,its that they dont run without fuel and i dont know how to fix the problem, all advice is appreciated. thanks everyone in advance
 
Is the tank cap vented? If is, try the generator with the cap loose. There has to be some way for air to enter the tank to replace the fuel as it's removed.
 
im not really sure ,its the cap that came on it at least when i got it ,i will try it tomorrow with the cap loose and see ,but its still hard to know because its not everytime that it does it,but i will give it a try, thanks
 
Another clue might be the level in the fuel tank. If the run time improves with a full tank of fuel, that could be an indicator of a pump mounted to high either by its suction rating or possibly a weakened pump.

Generally it is always best for the pump to be at the bottom level line of the tank. This allows a natural gravity flow to the pump once the flow has been started much like siphoning fuel out of a tank. Once the flow starts it will naturally continue if the end of the siphon hose is below the level of liquid in the tank. The horizontal distance may have some effect because of some higher vertical points along the run but if the fuel comes up from the tank and follows a level line then drops to the pump, I would not suspect too long of a run.

The cap issue is very possible. Another possibility is power to the pump. A drop in voltage results in a weaker pump.
 
the line is level with the gas tank top where it comes out and its level on the frame till it drops towards the generator.as far as the pump its new and if you sit a can of gas below it and let it pull from that ,it runs fine, but my old one ran the same way,i just got a new one because i hoped it would solve the problem,but it did not.due to the distance ,this is why they said i needed to put the pump at the tank because they said they push fuel better than pull it because they are a low flow rate pump.i just cant understand how they have been made on the side of it for years and now its a problem.
 
See what it does with  the gas cap loosened or removed. Be sure the tank level is the same as the last time it died.  If nothing changes then fill the tank and see if that does anything.

Once the fuel is sucked up out of the tank and begins its journey horizontally, most of the work is done and as the flow nears it's end, the pump is barely working. If the flow weakens after 20 minutes and the generator stops, I wouldn't suspect the length of run but I guess it is possible.

Could also be a defective pick up in the tank. I believe it is a metal tube that extends into the tank to the pickup inlet screen. Could be something defective there.


 
i have already had my tank off before ,it is like a big metal fabricated tank that came on it  and it has 2 pickup tubes that go evenly to the bottom of the tank and no screen at all ,the fuel level is at always at least a 1/4 tank and like i said, the tubes are even lengths ,so if the motor want run, the generator want either,thats just the way it was made ,nothing was changed from 1989.
 
Keep at it. Eventually you will find the answer. Hopefully sooner rather than later.
 
I am surprised that no one has mentioned the fact that the pickup for the generator is set higher than the pickup for the engine to prevent running the tank dry and being stranded.

The OP said that there is at least 1/4 tank of fuel in the tank.

Possibly the pickup is a little  higher than that.

Does it run continuously if you fill the tank?
 
both tubes are exact same length.. i know normally the generator tube is shorter ,but it was not made that way on this rv and it always has plenty of gas in it and makes no difference the fuel level when it does it , it just picks useally the worst times to cut off when i need it the most.
 
What kind of fuel line do you have?  Usually air in the filter bowl means it's being sucked into the line somewhere along the way.  Either a coupling that may be fuel tight but not air tight or microscopic cracks in the line.

Moving the fuel pump closer to the tank reduces the length of line that's under vacuum sucking fuel out of the tank and replaces it with pressurized line between the pump and the generator.  Something often overlooked if you have a metal fuel line is the rubber hose at the top of the tank between the tank outlet and the start of the metal fuel line.  It may not be air tight even if it doesn't leak fuel.
 
Lou is correct. If there is air accumulating in the filter, somewhere the air is getting in.

Air must be coming into the filter either at the filter or somewhere from the filter to the bottom of the pickup tube in the tank.

I suspect you are using a plastic filter? A plastic filter can fail and allow air to enter the system. Are you using an Onan factory filter?


 
One other question here, what type of fuel hose did you use when you replaced the old hose, is it carburetor fuel line or fuel injection line?  They are different, fuel injection line has a thin liner on the inside is designed to operate with a tank mounted pump under pressure, carburetor line is designed to operate with vacuum style fuel pumps mounted at the engine.  If you use use fuel injection line for your generator then it can collapse under vacuum, and what you may be seeing at the clear filter is not air in the filter but gasoline vapor caused by the vacuum being formed inside the line, much like the gasoline vapor that can cause vapor lock.
 
Agree with Lou - that's a sign of a crack in the fuel intake line, between the tank & the filter.  That allows the fuel pump to suck air instead of gas.  Apparently yours is an intermittent leak, perhaps exacerbated by changes in temperature, leveling the coach, etc. Something that physically moves the fuel line enough to open or close the crack(s).  The only real fix is to run a new line, though you might get lucky and find the spot to repair for a short term fix. Usually, though, more cracks will appear elsewhere until you replace the whole line.

Cracked rubber fuel lines are not unusual on vintage rigs like yours.
 
the fuel line has about 6 inches of 1/4 regular fuel hose at the clear filter at the generator and that connects to the fitting on the top of the tank ,i also replaced the clear filter last time it quit just in case because it was a cheap china filter and i replaced it with a name brand one and the rest of the line is a steel line and everything was new and it still would cut off after it all was replaced ,i slide the fuel line up onto the metal line a few inches and put 2 clamps on the end at the tank,so no clue how it could get any air in it.
 
the filter is up by the generator ,it has a 6 inch fuel line from the metal line to the filter and then a 3 inch fuel line to the fuel pump on the side of the generator.
 
i have no clue, i know i have had vapor lock problems with the motor because it has a mechanical fuel pump on the motor and a electric fuel pump back by the tank, this is another reason they said to move the pump to the back to push the fuel.i have no clue ..
 
Typical electric pumps do not suck as well as they blow. Most pumps recommend placement with 18" of the fuel source and below the fuel line. I know the factory Onan fuel pump isn't placed according to these rules, but it may be that it's designed differently.

When the gen is having one of these fits, is it repeatable? Or can you just restart the generator? Have you tried manually running the pump to see if the problem persists, or putting the suction side into a gas can and eliminating the long run from the main tank? Considered maybe something like a separate surge tank to see if the problem continues? (Not sure a surge tank is a good long-term idea, but for troubleshooting...)
 
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