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Old 06-04-2018, 11:40 AM   #1
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2000 33' Land Yacht
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No gas from gas tank to generator intake line

2000 Land Yacht with Onan Marquis 5500 BGM generator. I've disconnected the fuel line from the gas tank to the fuel pump and there is no gravity flow, no fuel comes out of the line. Should there be, or does the electric fuel pump 'suck' gas from the tank? I'm replacing the fuel pump without dropping the generator, so it's a bear to get to and I don't want to mount and hook up the new pump if I've got a problem in the line. Gas tank is over half full, engine runs.
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Old 06-04-2018, 01:45 PM   #2
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Your fuel tank will have to suction taps on top of the tank. No gravity feed.

One tap is for the chassis engine and the other will be for the generator. The generator tap does not sit down in the tank as far so it's possible the tank level is to low to feed the generator.

The quickest test would be to fill your tank and then try the generator.
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Old 06-04-2018, 02:27 PM   #3
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The generator fuel pump puts suction on the line from the tank. It is entirely possible that hose is cracked or leaking air from a fitting, so all you suck is air...

One way to check it is a hand-operated vacuum pump form the Automotive supply store--they make one intended for brake bleeding and other automotive tasks that require suction, like testing vacuum-operated switches and actuators.

They are (were) fairly cheap, and connecting it to the generator fuel line and putting some suction on it, then seeing if the vacuum is 'held' for a time will give you an indication that the line leaks or not. If you can suck up some gasoline into the brake bleeding container, then you probably have a good fuel line.

Others have noted that older motorhomes do NOT use gas lines that can withstand ethanol in gasoline. If your hoses are original, it's a darn good idea to replace every one of them with modern hose BEFORE you have a fuel fire. Too many of the old gasser motor-homes have been lost to leaky fuel lines dripping on hot engines....

Since you are messing with very flammable gasoline, do be careful about sparks, flames, or static electricity...you don't want to be center stage in a rapidly expanding fireball--that can easily ruin your whole day...
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Old 06-05-2018, 08:55 AM   #4
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No Gas to Onan Generator, thanks for the help

bkahler and rmkrum, Thanks for your help, your expertise is just what I needed. FYI, I think I'll hook up the new fuel pump, prime it, and hope that it works. I can temporarily mount it securely in an easier access location. If it doen't draw gas, I'll check the line. Will look into replacing the lines with something that will stand up to ethanol, thanks for the safety tip. Will take care to avoid sparking a fire. Thanks
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Old 06-05-2018, 09:54 AM   #5
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Easiest way would be as op says and fill the tank to make sure you are picking up fuel. If that doesn't do it, take a wire and run from 12v directly to the fuel pump lead. You should feel it running and if not take a screw driver handle or small hammer and tap fuel pump to see if it will start. If it hasn't run in a while it may be gummed up and stuck.
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Old 07-05-2018, 05:01 AM   #6
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any idea what the fuel sending unit part # is for 1984 excella 270? I have it in the shop and trying to get this replaced due to malfunctioning gas gauge. FYI; This is not a Chevy P30 tank or part...
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Old 07-05-2018, 05:16 AM   #7
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Originally Posted by Kvsterling View Post
any idea what the fuel sending unit part # is for 1984 excella 270? I have it in the shop and trying to get this replaced due to malfunctioning gas gauge. FYI; This is not a Chevy P30 tank or part...
If someone has replaced the OEM fuel tank and sending unit then it's anyone's guess as to what sending unit is installed now.

Why was the original tank replaced?
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Old 07-05-2018, 06:17 AM   #8
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Quote:
Originally Posted by bkahler View Post
If someone has replaced the OEM fuel tank and sending unit then it's anyone's guess as to what sending unit is installed now.



Why was the original tank replaced?


We have owned the 270 only a few weeks, so not sure of that history. Iím not even sure if this tank is OEM or not. The P30 chassis lists a 40 gal tank and ours has 60 gal. Our shop (not airstream) ordered a Chevy P30 fuel sending unit but is totally different from whatís on my vehicle.
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Old 07-05-2018, 09:36 AM   #9
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Originally Posted by Kvsterling View Post
We have owned the 270 only a few weeks, so not sure of that history. Iím not even sure if this tank is OEM or not. The P30 chassis lists a 40 gal tank and ours has 60 gal. Our shop (not airstream) ordered a Chevy P30 fuel sending unit but is totally different from whatís on my vehicle.
More than likely the 60 gallon tank is the original tank for your 270. The information I could find on the ViewRVs website indicates they had 60 gallon tanks.

As far as a sending unit, some of us have used this generic 90 ohm sending unit as a replacement for the OEM unit. The shop would need to bore about a 1-1/2" hole in the top of the tank for this one to fit.

The existing unit would likely have to stay in place if it has the fuel feed and sending unit as a one piece combo.

Pictures would be helpful if you can get them.
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Old 07-06-2018, 05:43 AM   #10
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That is very helpful, the shop reports the unit is sending a signal but the fuel gauge was bouncing from full to empty randomly and then pegged on full even though it had only 10ish gallons in the tank. Iím not convinced that the gauge isnít the problem. The tank is off now, thinking I may try a generic gauge to see if that is the fix. Otherwise I will tell the shop about the universal fit fuel sending unit
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Old 07-06-2018, 07:05 AM   #11
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Originally Posted by Kvsterling View Post
That is very helpful, the shop reports the unit is sending a signal but the fuel gauge was bouncing from full to empty randomly and then pegged on full even though it had only 10ish gallons in the tank. Iím not convinced that the gauge isnít the problem. The tank is off now, thinking I may try a generic gauge to see if that is the fix. Otherwise I will tell the shop about the universal fit fuel sending unit
A generic gauge likely won't work with the OEM sending unit. If you're going to swap gauges just remember in the 70s and 80s the GM set up is 0-90 ohms for the gauges. The sending unit in the link I sent you was for 0-90 ohms. You can also buy a different sending unit and gauge that are 240-33 ohms which I believe is the more modern equivalent.
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Old 07-13-2018, 05:09 AM   #12
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That worked, thanks for the suggestion!
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Old 07-13-2018, 01:59 PM   #13
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From memory, I think some of the Motorhome had different tank capacities from the standard P30 chassis. It's probably all set out in the Motorhome chassis guide on the site. For info, P30 chassis gear is usually correct, but technically you have the P32 (Motorhome) variant. Some parts, not many, vary from the P30.
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Old 08-10-2018, 06:06 AM   #14
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Well the eBay fuel sending unit was the answer. Cheaper than trying to replace and it is accurate. Thanks a ton for the advice, the shop had no idea how to solve this one
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