Generator flooding when MH is running

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427v8

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OK I have an old Generac on a '92 gasser class C that runs fine ( now that I rebuilt the gens carb ) when I'm parked.
However when the MH engine is running it very quickly floods. And I mean floods like New Orleans, gas pours out of the carb, the float is totally overwhelmed.

My first guess is that the MH's evaporative fuel recovery system is bad and it builds too much pressure in the lines. But I opened the gas cap and it still floods, Grrrrr.

Would the MH fuel pump be pumping fuel to the Gen???

Anyother guesses before I tear into her?


Just a few more bugs to fix on this old Motorhome and she'll be ready to go...
 

King

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Does your motor home have fuel injection?  If so, the fuel pump actually may be in the fuel tank. Typically, a fuel injection pump runs about 40 pounds pressure, so you can't connect a generator to the gas line.
 

427v8

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Well it IS a fulie but there is a special gas line for the Gen and I assume that it is supposed to work...

I suppose I should hook a pressure gauge to the fuel line to see what I'm up against.
 

John From Detroit

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I had an old dodge maxi van that did that,  both runing and espically parked

Turns out the fuel pump was dying and as bits and pieces of the diaphram flaked off they were clogging the needle valve in the carb  and holding it open.

I cleaned the valve (It is the valve controled by the float) and installed a fuel filter. Then I replaced the pump

NOTE any debris in the fuel line post-filter can do this

Mis-adjusted float will too but I suspect dirt in the needle valve
 

Karl

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427v8

I guessing that the Generac was added after the "C" was built, and possibly whoever did it tapped into the main line from the fuel tank after the pump. A factory install would have had a seperate fuel line from the gas tank, gravity fed, leading to the genset. If this is the case, the carb float/needle valve on the genset is not designed to handle all that pressure. Also, the float may have developed a leak and had taken in some gas, which would make it think the float chamber is not at the proper level and lets in more gas than it should. If it's the first situation (fuel line), you could install a fuel pressure regulator inline, or fix it properly by installing a separate, non-pressurized line in the tank about 1/8 -1/4 from the bottom. That's so your genset doesn't run your rig out of fuel without enough left to get you to the next gas station. When you rebuilt the carb, did you shake it around to see if there was any gas inside? Also, did you adjust the float level by bending that little tang on it? Some carb rebuild kits come with a new float, or have replaced the older solid brass needle valves with one that have Delrin inserts. The inserts make them a little longer than original, so an adjustment is needed.
Question: For the flooding to occur, does the engine actually have to be running, or will it flood with the key merely in the "run" position but engine not runniing? 
 

427v8

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Well here's what I found.
I put a fuel pressure gauge on the line before the Gens pump. when I turned the key to ON the fuel pressure pegged the 10 PSI gauge!

So it looks like the MH's fuel pump is feeding the gen, grrrrr
I can't see where the connection is made to the tank, I'd have to drop the tank. which has 40 gallons of gas in it right now, so I guess I'll have to wait till come back from a trip or something...

At least it now runs good with the Mh stopped :-D
 

Alaskansnowbirds

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427v8 said:
Well here's what I found.
I put a fuel pressure gauge on the line before the Gens pump. when I turned the key to ON the fuel pressure pegged the 10 PSI gauge!

So it looks like the MH's fuel pump is feeding the gen, grrrrr
I can't see where the connection is made to the tank, I'd have to drop the tank. which has 40 gallons of gas in it right now, so I guess I'll have to wait till come back from a trip or something...

At least it now runs good with the Mh stopped :-D


427v8,

As a temporary fix install an in-line valve. That way you can drive the MH without flooding the gen set. If you have to use the gen set while stopped just open the valve. This will get you by until the fuel tank is near empty or you have time to do a permanent fix.
 

427v8

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Karl,
Great Idea, I'll have to try it, besides I get the feeling that installing a seperate feed would be a PITA
 

John From Detroit

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One issue with tapping the line to the main engine (Vehicle engine)  In a factory install there are two fuel outlets in the tank, one is higher than the other, so, for example, last Summer when I was running the generator to power the AC during takedown... It quit running... I was wondering "What now" till I fired up the main engine and saw I was below 1/4tank.  Generator worked perfectly after a visit to a fuel pump
 

Gary RV_Wizard

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I put a fuel pressure gauge on the line before the Gens pump. when I turned the key to ON the fuel pressure pegged the 10 PSI gauge!

One has to wonder how it ever worked, if that is the case.  Maybe it didn't.  But if it did, then it seems to me as though something must have changed to cause this problem. Perhaps something in the carb rebuild is not up to the task? 

High pressure fuel systems usually have a return line that lets excess fuel flow back into the tank. Mabe you could rig one for the genset?
 

427v8

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Well it never worked for the PO, I don't know who the fist owner was, But I'm guessing either he or a non RV savy Mechanic replaced the sending unit and either hooked up the Gen Fuel line wrong or used the wrong sending unit and had to tap the pressurised line.

I will fix this the right way eventually, but I don't feel like messing with 40 gallons of gas right now. I have a shut off valve in the fuel line now, maybe I'll just suffer without running the gen while driving for a while.

I think this has been an issue for a while, the 1992 era gen only has 154 hours on it! thats barely 10 hours per year ::)
 

Gary RV_Wizard

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I know there are fuel pressure regulator available, but have never looked into the details.  At least some of them require a return line for a place to dump excess fuel to relieve the pressure.
 

427v8

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I bought a cheap one from checkers auto. It's an inline job, adjusts from 1 to 5 psi. Should do the job, I'll find out as soon as it quits raining :mad:
 

427v8

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It works!!
I plumbed in the regulator, set it to 1 PSI and fired her up. She ran good.
I started the MH and no fuel overflow :)

I loaded it up, ran the microwave, lights, fans ( too cold for the AC to come on ) and the gen seemd to be struggleing a bit, so I cranked the regulator up to 5 psi and she smoothed right out, sweet.

So it runs good, I still plan on fixing it the right way, but at least now it will work !

Keith
 

Shayne

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Great  Just goes to show you that the experts in this forum can solve darn near everything and anything,  Sometimes they have to butt heads and do some digging but believe me they are the best.  They certainly don't get enough credit for all their knowledge.
 

427v8

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I agree and want to thank everyone who helped!

Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou, Thankyou,

;D ;D
 
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