Diesel Tank Fuel Lines

One problem leads to another

When we returned from our cross Canada trip in September of 2019, we discovered a small fuel leak coming out of the bottom of the passenger side diesel tank. It was a small leak, but enough to create a small stain on the tarmac over a period of a few days. So we needed to get it fixed.

During the process of repairing the leak which was located in one of the end cap weld seams, the mechanic who was removing the tank from the truck had an unfortunate problem with the fuel lines.

Our truck has two fuel tanks, and the two tanks are connected to each other via a T-fitting. This allows fuel to flow from one tank into the other so the fuel is drawn equally from both tanks by the engine. The problem the mechanic had is that when he pumped out the leaking tank, and then removed the fuel lines, fuel from the other tank rushed through the connected lines and out onto the floor. There were no shut off valves on the driver side fuel tank.

Now one has to ask the obvious question as to why the mechanic didn’t look to see if there were indeed valves to close on the driver side tank. After all, this is what these mechanics do all the time in a body shop. So his attempt to solve the problem was to leave the fuel lines attached to the two valves on the leaking tank, and then back the valves out of the tank so they remain on the hoses and block the fuel from draining from the driver side tank. Just one problem. When he started unthreading the valve from the leaking tank, he didn’t notice that the valve was not unthreading from the tank, but rather was unthreading from itself. In other words, he was disassembling the valve body. When he finished unthreading the valve, the two halves of the valve that when screwed together hold the ball and seals in place, split apart, the ball fell out onto the floor, and the diesel from the other tank once again started pouring onto the floor. But this time he couldn’t quickly replace the part so the leak could be stopped. Ten gallons later, the mechanic managed to stem the flow of diesel from the 1/2” I.D. fuel line.

When the tank leak was fixed, the mechanic re-installed the tank and fuel lines. Just one problem. When he inadvertently disassembled the shut off valves, and put them back together, he did so without ensuring that the valves themselves didn’t leak. So although we got the tank leak fixed, we now had a bigger leak coming out of both shut off valves.

Of course it wasn’t until after we took the truck back to the storage facility, that we discovered the next day a new puddle of diesel on the ground. Now trying to get the truck back into the body shop to get this problem fixed was virtually impossible. Although it was the shop’s screwup, the overflowing shop couldn’t fit us back in for weeks, if not months. Trucks used for commercial use took priority over us non-working folk.

As is so often the case, it was now up to us to repair the repair. The problem, though, was that there was still 3/8 of a tank of diesel to deal with. It had to be pumped out in order to disconnect the fuel lines and replace the valves. That’s around 95 gallons of diesel, and we didn’t have any 45 gallon drums to pump the diesel into like the body shop did. So we had to get creative.

The supply and return lines for both tanks enter about halfway up from the bottom of the tank. Since each tank was 3/8 full, it was possible to pump the diesel from one tank into the other tank while the fittings were worked on. Since we had valves on the passenger side tank, albeit leaking ones, we could pump the driver side diesel into the passenger side tank, and close the valves. To do this, however, we had to buy a diesel transfer pump, hoses and fittings. All these we were able to source from Princess Auto, and Greenline Hose. Once assembled with a short hose and long hose, we were able to transfer the fuel quite quickly. The pump is self priming and works at ten gallons per minute.

Once the driver side shut off valves were installed, we were able to pump the diesel from the passenger side tank over to the driver side tank and close the new valves there. Then we were able to remove the old damaged valves and replace them with new ones as well. All this because some dummy of a mechanic worked on our truck.