19 May, 2014 - Gas Tank Repair

If you've been reading my blog you know we are working on a motorhome we purchased last fall to get it ready for a summer road trip.  So far everything's gone smoothly.  It needed a windshield wiper motor which I knew about before the purchase and I suspected the gas gauge didn't work.  The first major surprise came when we filled the gas tank.  It was leaking around the fuel gauge sender unit.  So ... I ended up removing the sender unit to do some repairs.

 

The first thing was to get the back elevated enough to work on the tank. The right rear tires are on high ground so I needed a way to get the left side up as well.

 

That was accomplished with my redneck ramp.  I used some sawmill slabs and 2X4's to build a ramp.  The center (bottom) 2X4 supports the weight of the vehicle.  I used a chink of split firewood as a wheel block.

 

 

The leak was a steady drip but it's spread so far from the source that it needed some cleaning to find the precise location.

 

Here's a closer view of the fuel sender unit.

 

There was a secondary leak at the fuel filler hose where it enters the tank.  I just needed to tighten the hose clamp to fix that.

 

I used my small Oxygen/Acetylene torch to solder the leak shut.  I purchased this for $60.00 at a pawn shop a few years ago.  It works great for small jobs but with the small tanks it will empty them in a hurry when using it for cutting jobs.

 

 

The previous owner obviously knew of the leak since they'd attempted to repair it using commercial gas tank sealer.  The steel tube is the fuel supply line that goes into the tank.  The fuel pump draws gasoline through this tube.  The tube is supposed to be a tight fit but it was loose, allowing gasoline to leak past where it enters the tank.

 

The two electrical connections (with the small nuts) go to the fuel gauge sender attached to the steel tube.  I apologize for not having a photo.  I tested the sender unit with an ohmmeter and it didn't work which meant it may have had some internal damage.  I thought maybe I could fix it if it survived soldering the tube back in place.

 

So I made my first attempt to solder the tube with the electrical connections intact. You can see the bottom of on connection in the photo (it's the orange disk behind the small tube).  The orange disk is a plastic insulator and I applied a steady drip of water to it while soldering the tube.  My attempts to keep it cool didn't work though and I melted enough of the plastic that it was loose in the housing.

 

So I drilled it out along with the ground connection then used a wire brush to clean up the rust.  I used a steel pop rivet to plug the small hole in the center of the round plate and used a small bolt and nut to seal the larger hole.  I then put a bunch of solder over both to seal them up and keep them from leaking.  I soldered the two tubes to the steel bracing shown to reinforce them as well.  I used silver solder on the joints because it is stronger than plain lead solder.  If I had known I couldn't save the sender connections I'd have brazed the joint.  Brazing gives a much stronger bond but it takes a lot more heat to do it.

 

I also applied the solder liberally to the outside surfaces to ensure there would be no leaks once it was installed.  I refilled the tank and the leak is fixed.  The fuel gauge still doesn't work but we can live with that for awhile by keeping track of the miles when we fill the tank.  I taped up the wires to the sender unit.  If we keep the motorhome we'll get a new sender unit when we get back from our road trip.  If do not keep it the next owner can replace the sender unit.  (I will, however, let them know what I've done and why it needs replaced!)

 

You can see a brass plug in the gas tank at about the seven-o'clock position below the fuel sender.  A previous owner drilled a hole in the tank to drain the fuel down below the fuel sender (I'm assuming to apply the sealer).  It sealed up okay with the plug but doing that isn't necessary when working on gas tanks that do not have the pump in the tank.  It's very easy to siphon the fuel from the tank using the fuel line itself.  Just remove the hose that goes to the fuel pump and install a siphon hose.  Now you can siphon fuel directly from the tank and into a suitable container.  It's a lot easier than trying to shove a hose down the tank filler neck.  (Especially when it's about four feet long as it is on the motorhome.)

 

I use hose and primer bulb designed for outboard boat motors.  It's safe with gasoline and long enough to fit to the bottom of most gas tanks and it works (unlike the cheap plastic siphon hoses sold at most discount stores).  Using the primer bulb to start the fuel flowing is much better than getting a mouth full of gasoline! 

 

Anyway, the leak is fixed and though I'm disappointed that I didn't get the gauge to work we can live with that for this trip.