Out of gas after at 16.4L

[eeshed]

Hey there,
It is the second time that my 1985 FJ1100 stalls when the gas is low, but not entirely empty. It would start hesitating, jerking, backfire, and eventually die mid ride. If I wait a minute it would restart, allowing me to find the nearest gas station. I'd estimate I rode about 210 Km before it started acting. When I topped the gas tank it took only 16.4 litters. In other words, there is another 7.6 litters of gas in the tank when it decided to run our of gas.
Is it normal? If not, what may be the problem?
Thanks,
Eyal

[Dads_FJ]

The cap might not be venting and thus creating a vacuum in the tank.  Try just opening the cap or riding with it cracked.

[red]

Hey there,
It is the second time that my 1985 FJ1100 stalls when the gas is low, but not entirely empty. It would start hesitating, jerking, backfire, and eventually die mid ride. If I wait a minute it would restart, allowing me to find the nearest gas station. I'd estimate I rode about 210 Km before it started acting. When I topped the gas tank it took only 16.4 litters. In other words, there is another 7.6 litters of gas in the tank when it decided to run our of gas.
Is it normal? If not, what may be the problem?
Thanks,
Eyal

Eyal,

Sounds like you may have rust or debris in the gas tank.  Start with a full tank, outside, and siphon out a lot of the gas with a small hose, using the end of the hose to run around the bottom of the tank.  Work around the petcock, inside the tank, especially.  If your "vacuum cleaner" hose dumps a lot of junk into the "catch" container, that is very likely the cause of your problem.  You may want to take more aggressive action to clean out the tank, in that case, but this will be a good first step, in finding the problem.  Once you let the "catch" container sit (capped off) for a day or so, you can put most of that gas back into the tank, but you may want to run it through a big funnel with a coffee filter (or fine mesh screen) taped inside.  Try not to agitate the container, as you do this, and do not try to get the last (worst) liter of gas back into the tank.

A kinked or pinched gas tube may also be the problem, but you would need to remove the gas tank, to find that.

Cheers,
Red

[ribbert]

Hey there,
It is the second time that my 1985 FJ1100 stalls when the gas is low, but not entirely empty. It would start hesitating, jerking, backfire, and eventually die mid ride. If I wait a minute it would restart, allowing me to find the nearest gas station. I'd estimate I rode about 210 Km before it started acting. When I topped the gas tank it took only 16.4 litters. In other words, there is another 7.6 litters of gas in the tank when it decided to run our of gas.
Is it normal? If not, what may be the problem?
Thanks,
Eyal

There could also be a restriction somewhere, most likely the fuel lines. It gets very hot under there which can cause a poorly routed line to kink as it heats up. Even if you haven't been playing around with them, age can bring it on.
As the fuel level drops so does the head pressure until it reaches a point where there is insufficient weight in the fuel to push it through.

If this was the case, the few minutes you wait would allow enough fuel to trickle through and restart.

The symptoms you describe are consistent with running out of fuel.

Noel

[eeshed]

Thank you all,
The tank looks clean from rust. I am leaning towards the negative pressure in the tank, and possibly a restriction of gas flow in the pipes. a) any information available about servicing the venting of the tank? b) any recommendation for a gas line replacement?
Thanks,
Eyal

[Dads_FJ]

Thank you all,
The tank looks clean from rust. I am leaning towards the negative pressure in the tank, and possibly a restriction of gas flow in the pipes. a) any information available about servicing the venting of the tank? b) any recommendation for a gas line replacement?
Thanks,
Eyal

Why yes!  http://www.fjowners.com/index.php?topic=2024.0

[eeshed]

Update: yesterday I was riding when the fuel gage got below half. At that point I knew that the bike will start stalling and eventually the engine will die. I decided to experiment as there is about 1/2 a tank of gas. Once the bike died, I opened the gas cap to let pressure release. This procedure allowed me to ride for another few minutes before the bike died again. So, I took the decided to change the petcock position from Pri to On. In other words, to allow for a free flow of fuel regardless of the vacuums. That procedure allowed me to extend the ride further. It looks like there is a link between the level of gas in the tank and the petcock. Further more, the most peculiar was the engine was running smoother, less vibrations, while the petcock dial was on On (i.e free flow.)

1) What may be the issue that stops the fuel from getting to the engine at mid tank? Is it a bad petcock? Weak vacuums line?
2) Why the engine would run smoother? Could the petcock impact the mixture?

Thanks,

Eyal

[FJ_Hooligan]

You've got the functions backwards.

PRI = Prime, and will flow fuel without vacuum (engine running or not).

ON = On, and will only flow fuel when intake vacuum is present (assuming the diaphragm is in good shape and the o-ring is working).

[Pat Conlon]

Yeppers, Time for a new petcock....FJ Monkey (Mark) just went through the ordeal.

[FJmonkey]

If your tank is vacuum locking, take your fuel cap apart and clean it out. Be very aware of how the parts come out and the orientation of them for proper reassembly. Don't ask me how I know.... Just pay attention.

Point of clarification, PRI = prime, free flowing regardless of carb vacuum, RUN = flows only when engine is running and vacuum opens the valve. You should not leave the bike on PRI as any small amount of crud in the needle seats will empty your tank on to the ground, or into your crank case. One is a big fire hazard, the other can hydro lock your engine and break internals when you try to start it. Switching from PRI to RUN will have no effect on a properly working petcock. Clean your cap....

While you are under the tank, perform the SUCK test on your petcock. That's right... Suck your petcock!!! Remove the vacuum line from the carb, make sure your petcock is on RUN, make sure the fuel line is positioned safely to drain fuel into a container. Suck on the vacuum line. You will get one of two results. You can suck very little and it seems like sucking on a straw that is plugged and nothing comes out. The other result is you can keep sucking as if the straw has a hole in it and is letting air in. That one is the bad one. Very tiny holes will still work properly but will get worse with use. If your petcock fails the suck test then you need to get a new one. It lasted almost 30 years so a new one will take you into many miles.

Randy at RPM gave me a really great deal on mine when I need one. I told him the FJowner's secrete pass phrase "I sucked on my petcock and it failed". I paid the list price and he sent me a new one in less than a week. 

[eeshed]

Great new action. I never though it would come down to sucking. Well, I got to try. Sounds like a great Sunday project.
Thanks all,
Eyal

[Bryce]

I had my petcock stop working recently; went to take the tank off the bike and the gas didn't stop flowing, so the vacuum shut-off wasn't working.  Took the petcock off the tank, cleaned everything with gasoline, put it back together the way it came apart, and it worked again.  It's worth a shot - those petcocks are pretty expensive.

[FJmonkey]

Did you suck it?

[Charlie-brm]

I would have gone straight to the petcock, knowing that my reserve light comes on full intensity with 7 litres left. FJ1100 - 24.5 litre tank - 7 >>> pretty close to the fuel you have consumed when the problem pops up.
On my FJ1100 the visual check is when the fuel is just sloshing about even with the top of the center hump when looking into the tank. And at that point, I can't put in more than about 16 to 17 litres.

[eeshed]

Here is an update. The sucking test failed. It keeps losing pressure while sucking. Ok, I guess I need a new petcock? How about plunging a Pringle valve in line while the petcok is left open?
Eyal