Fuels Starvation

[82gl1100iwingman]

My 79 GL1000 seems to be having a fuel problem and was hoping for some ideas.

The fuel pump gets starved for fuel and with no fuel, bike stops running. I have a glass Moroso fuel filter on it and can see that there is no fuel, Gauge will show plenty of fuel and there is plenty fuel. When this happens, I will take the fuel line that comes from the tank off the fuel pump and there will be air being sucked back into the tank. Once the air pressure equalizes, I will blow on the fuel line and hear the fuel making bubbles in the tank and to get it siphoning again. Hit the starter button and after the carbs bowls get filled, off we go again like there was n problem. This normally happens when the bike sits for about a month or when I am riding and have to switch to reserve. My first inclination is that my fuel pump is on the way out or my fuel cap isn't properly venting creating a massive vacuum in the tank as it gets emptied. Any thoughts are appreciated.

[CYBORG]

Sounds like the vent in the fuel cap is not working. try removing the cap when it happens, and see if fuel flow returns

[robin1731]

Yeah, try running with the cap loose and see if goes ok. It does sound the vent is plugged.

[jdvorchak]

Actually it sounds like your fuel tank is dirty and plugging the outflow tube.

[robin1731]

This statement makes me think otherwise. " I will take the fuel line that comes from the tank off the fuel pump and there will be air being sucked back into the tank. Once the air pressure equalizes, I will blow on the fuel line and hear the fuel making bubbles in the tank and to get it siphoning again."

[jdvorchak]

you know robin, after I read it again I tend to agree with you. I was wrong. you know what I was thinking that the screen was getting plugged with rust etc. and not allowing fuel to flow. Then when he blew into it that would clear the screen and fuel once again flowed.

[olchris]

Actually it sounds like your fuel tank is dirty and plugging the outflow tube.

Over flow tube..... Sorry i dont get what you mean!!

[olchris]

Sounds like the vent in the fuel cap is not working. try removing the cap when it happens, and see if fuel flow returns

+1 .. Its usually the simple things IMO....

[todd54219]

It does sound like the vent in the cap is plugged or stuck closed. Make sure you have 3/4 to a full tank of fuel, it will make things easier. Also make sure the filter is not plugged up as well. Run the bike on the stand until it dies again. Pull the fuel line from the tank to the pump and place the end in a container. Then open the fuel cap and see if the fuel flows. If it does it is the vent in the cap. If not, you could have some blockage, rust, in the tank which is clogging the fuel pickups in the tank. If that is the case, you will need to clean out the tank.

Good luck and let us know what you find.
Todd

[82gl1100iwingman]

I haven't seen any rust in my fuel filter, but that's not to say the there isn't any that could be clogging the pick up screen. Does anybody know of a part number for a aftermarket fuel cap? I think throwing a known good fuel cap at to see if that fixes isn't bad.

[olchris]

I haven't seen any rust in my fuel filter, but that's not to say the there isn't any that could be clogging the pick up screen. Does anybody know of a part number for a aftermarket fuel cap? I think throwing a known good fuel cap at to see if that fixes isn't bad.

Yep do it...... even your suspect cap, put it back on and dont "Lock" it down so that you know that air will flow through.... Even a rag, racing tape up the tank inlet with a few pin holes to eliminate the vacuum ...

Must ensure the tank doesnt create a vacuum when the fuel is used up... Once your absolutely sure a vacuum is not created with fuel usage you can then go on to assess other issues like flow, blockages, fuel pump, tyre pressure or any random thoughts.... Got to start at the beginning, not halfway down the circuit if your sure to eliminate a fuel starvation issue!!

[olchris]

Have you had a look in the tank???

Eg remove the sender (under the seat) had a look with a good torch/light...???

[hmratbam]

You could soak the cap in vinegar overnite or boil it in distilled water for awhile.

[tlbranth]

You could soak the cap in vinegar overnite or boil it in distilled water for awhile.

I'd pass on the vinegar. Tried that. Took most of the cadmium plating off and now the cap is a pile of rust. Also rusted the pliers I used to pull the cap out.