Auxiliary Fuel Operation MEP 803a Bubbling?

[1stinlastout]

I finally got my 275 gal fuel tank set up and plumbed to the genset. When switch from off to Prime Aux I can hear a bubbling in the fuel tank. Is this normal? Also, how do you tell if it is running on Aux fuel?

Thanks

 

[Light in the Dark]

Are you certain you hear bubbling? You should be hearing a dribble of the fuel being returned to the tank. The set never runs on an auxiliary fuel tank... it simply refills itself via double float switch. I would suggest brushing up on the TM for the unit to get a better understanding of the hows and whys.

 

[1stinlastout]

Are you certain you hear bubbling? You should be hearing a dribble of the fuel being returned to the tank. The set never runs on an auxiliary fuel tank... it simply refills itself via double float switch. I would suggest brushing up on the TM for the unit to get a better understanding of the hows and whys.

Thanks, I did see that in the diagram. I can definitely hear bubbling. I think it's just air in the system. I guess I just need to run it for a while and see.

 

[Light in the Dark]

These machines are self priming. The amount of air in the system would pass rather quickly under prime, and definitely not be sustained. Is your return line dumping back to the stock tank in the machine, or to this larger external tank?

 

[Light in the Dark]

OK let me back up... it is possible that you are sucking air if this only happens under PRIME AUX, as its a pulling line, versus a pushing line. Did you fab up the fuel hose from the external tank to your machine, or was it factory made? Have you checked any of the fittings behind the fuel tank panel?

Sorry I did not fully read the first post about the AUX setting.

 

[1stinlastout]

These machines are self priming. The amount of air in the system would pass rather quickly under prime, and definitely not be sustained. Is your return line dumping back to the stock tank in the machine, or to this larger external tank?

The return line goes to the inside tank. I have the aux fuel line attached on the port next to the fuel cap.

 

[1stinlastout]

I found this vent at Grainger.

 

[1stinlastout]

I ran out a while and it seems to have stopped bubbling noise. I think we are good.

 

[Daybreak]

Howdy,
First, do you know how the aux fuel works?
The MEP generator has a internal fuel tank. Sometimes called a day tank. When the S-1 is set to make use of the aux fuel, the day tank is used. When the day tank gets low (adjustment can be made here) it turns on the aux fuel pump. (Aux Fuel connection by the fill cap) That fuel is added to the day tank. It automatically shuts off when it gets around 80% full (This can be adjusted) The sequence of auto filling will continue until there is no fuel left in the aux tank. The generator will keep operating until that day tank is just about empty, and at that time, you will get a "Fault" Low Fuel, and the generator will shut down.

NOTE: Do NOT trust the aux fuel refill to work.

Test it out. You can manually reach in the fuel tank and moves the floats to simulate a low fuel condition. The same thing for the float level to signal aux fuel pump to stop.
We had members which ended up with multi-gallons of diesel on the floor.
Another testing method, would to have it all connected and running, use a siphon hose to empty the day tank, watch and listen to when the aux pump kicks on. Note the fuel gauge level. Watch and listen to when the aux fuel shuts off. 70-85%. This can be adjusted overall with the exact height of the dual float fuel level sensor. The important part is that it actually shuts off the aux fuel pump. If not, you could have 275 gallons on the floor.

 

[1stinlastout]

Thanks for the detailed info. I'll check out the float to see if it's working.

 

[1stinlastout]

Thanks for the detailed info. I'll check out the float to see if it's working.

Well, I finally figured out the mystery of the bubbles. The aux fuel pump was hooked up backwards. Probably during some field maintenance.

 

[Light in the Dark]

So the pump was inverted, or someone rerouted the fuel lines? One is a hard line, so thats not the easiest to accomplish. At least it was figured out.

 

[Ray70]

Sounds like someone probably replaced the aux pump and inverted it, making it flow backwards.
With that said I suppose then the bubbling sound was in the aux tank and not the gen's tank??