The Mite
Part: 16
Adding a sump and pipe fittings to the gas tank

blank sump Going from a car and gas tank that was designed for a carbureted set up to a fuel injected engine requires a return line from the engine to the gas tank. The fuel pressure regulator returns unused gas to the engine to maintain the proper fuel pressure in the injector rail. In order to have two fittings on the Mite's tank, I decided to weld on a small sump ( I could have bought a Fuel Tank Sump Kit but i decided to make one)and put the pickup and return lines on it. This is the sheet metal sump, bend and welded. I made a cardboard template and used that to cut the sheet metal.
sump on tanks Here's the sump on the bottom of the new gas tank. I have the tank that came with the car, but there are a few rust holes and it's never a good idea to weld on a used tank. Even if the tank has been empty for years, there's still a chance of explosion when welding. Yeah, many people say "just fill it with dry ice" or "plug the fittings and purge it with argon" well, I'm chicken and decided that a new tank was cheap insurance to keep my limbs intact.
cheapo fittings Instead of ordering pricey weld in Fittings with internal pipe threads, I decided to make my own. Here's a couple of 3/4 to 3/8 pipe fitting adapters. It took just a couple of minutes with a grinder to remove all the zinc coating and round out the heads..then they were ready for welding.
sump with holes and fittings Here's the custom, ground down fittings and sump with holes in it
sump with fittings The custom, $0.75 weld-in pipe fittings inserted in their respective holes
sump welded Here's the sump welded onto the tank. There's 3 holes, each 1 1/2 inch diameter drilled through the tank to allow gas into the sump. I also carefully ground away all the galvanized coating on the tank to allow for a perfect weld. The brass fittings and hose-clamped braided line are just to check for leaks
sump done I filled the tank with water and let it sit overnite and there were no leaks. Just to be sure, I will coat the inside with a gas tank sealant.
side view of sump The sump with temporary braided lines to test for leaks. One of the fittings will be the gas supply to the fuel pump and the other fitting will be the bypass return from the fuel pressure regulator. The little sump will also help prevent fuel starvation during the massive acceleration and cornering forces the car will see......
sender top The Dolphin gauges came with their own fuel level sender, which, of course, did not match the mounting holes in the stock Sprite tank. I checked the outputs of the Sprite sender vs. the Dolphin sender and they were different, so I could not use the stock fuel level sender. I welded up the holes in the Dolphin flange as seen here, then drilled new holes to match the Sprite tank.
fuel level sender parts The Dolpin fuel level sender is adjustable for any size tank. Here's the parts.The mouting rod on the top and the bar that holds the float need to be shortened to work in the Sprite tank
senders This is the sprite sender next to the modified Dolphin sender
sender in tank Here's the sender in the tank. The new tank does not use the same whitworth threaded screws as the Original 1965 tank did, so I'll have to get some 8-32 screws to hold the sender in the tank.

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