By Greg Illes
For years I struggled with my fuel filling speed. Sometimes, gas would flow into the tank without complaint. Other times, I couldn’t get more than a trickle before the nozzle would auto-shutoff. It was maddening, especially for those 40-gallon fills, which could take (literally) a half-hour.
Of course, I checked the filler tube for blockages and kinks — there were none. I played with the angle of the spout and the filler neck, too. No help.
Finally, one day when I was checking out something else, I noticed that my filler had an external vent line. This is very common, but because it was hidden by the larger fill tube, I had never noticed it. The vent line had a droop in it, just an inch or so, but it dipped down and then came back up. No leaks or kinks, just a droop.
That droop was key, because it acted like a sink trap and collected gasoline in the dip. When the gas filled the dip, no vapor could get through and presto: trickle fill time. I trimmed off a short piece of the line and reconnected it so that the droop was eliminated. Then I drove the RV to the gas station. Hooray! Full throttle fill, no shutoff. I felt released from bondage. Several tankfuls later, everything is still working great.
If you have no issues with filling your tank, super. But check the lines anyway as a preventive measure. If you do have problems, check both the fill tube (large) and vent tube (small) for smooth, kink-free downhill routing. No dips or droops, please.
Note that some fillers have coaxial venting (my Ford Ranger is one of these). These are much harder to see and troubleshoot, but it is possible with some patience and possibly a bit of disassembly. As always, if you are not comfortable, confident and safe while working with fuel systems, hire a pro.
photo: Mariordo / Wikipedia
Greg Illes is a retired systems engineer who loves thinking up RV upgrades and modifications. When he’s not working on his motorhome, he’s traveling in it. You can follow his blog at www.divver-city.com/blog.