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Topic: Fuel level sending unit and generator shut off (Read 7969 times) previous topic - next topic

Fuel level sending unit and generator shut off

My understanding is that the generator cuts off once the diesel tank reaches a quarter tank. How does this work? Does it start sucking air at a quarter tank, or is it triggered from fuel level sending unit?
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My fuel level sensor was completely unreliable. I actually watched it climb from 3/8 to over 3/4 one time . I was in nacogdoches couple weeks ago and asked Keith about it, he said no problem - it's just a sensor that sits on top of the tank that reads the fuel level by laser or something, not mechanical at all.

So it works great. Now, after a fill, it reads full like it should. The part was bought from Foretravel, they calibrated it for my tank, and it was installed.

I'm sharing all this cuz I assumed we would have to pull the tank, in order to pull the sensor, but the whole deal seemed pretty straightforward.

However, today we got about 350 or 400 mi on the tank with about 24 hours of generator time, and I decided to fill it up. Previously I was going upwards of 600 mi or so and I would put in 100 or 110 gallons and I believe my tank holds 150.

The new sensor in it was showing a quarter of a tank, so I expected to put in about 110 gallons. Instead, the pump shut off at 91 gallons.

So I'm not sure how accurate it is, but more so, will my generator be cutting off prematurely?  Ie, shutting down it about 20 gallons before it should.

Steve and Cassi
2007 Foretravel Nimbus 42'

Re: Fuel level sending unit and generator shut off

Reply #1 –
Fuel pickup is at the 1/4 tank level.  Generator will die when it starts sucking air
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Fuel level sending unit and generator shut off

Reply #2 –
Nice - hopefully I'll never see that level, but good to know - thanks!
Steve and Cassi
2007 Foretravel Nimbus 42'
 

Re: Fuel level sending unit and generator shut off

Reply #3 –
Quote from: stevej –
My understanding is that the generator cuts off once the diesel tank reaches a quarter tank. How does this work? Does it start sucking air at a quarter tank, or is it triggered from fuel level sending unit?
To answer your question with more detail, IF the newer coaches are setup the same as the older ones, then it works by "sucking air".

In the fuel tank there are two fuel pickup tubes.  The tubes are suspended from the top of the tank.  The open bottom end of the tube that feeds fuel to the main engine is fairly close to the bottom of the tank.  The open end of the tube that feeds the generator is a bit higher above the bottom of the tank.  As the fuel level drops inside the tank, it will get to a point below the generator pickup tube, and of course the generator engine will suck air and die.  You will still have some quantity of fuel above the end of the other main engine pickup tube, so that you can (hopefully) make it to a refueling station.

Diagram below of typical tank with dual filling ports is applicable to the late 90's models.  It illustrates the general concept of dual pickup tubes (located near the center of the tank), but may differ from tank design in the newer coaches.  At what point (on the dash fuel level gauge) the generator engine dies, and how much fuel remains in the tank at that point, will depend on the exact placement of the fuel pickup tubes.

It is STRONGLY recommended that you avoid running either engine out of fuel, except in extreme emergency situations.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
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