The fuel tank sits in the boot, mounted on rubber strips on the boot floor. Two distinct tank designs were used during production, and the sender unit, filler cap, and filler pipe arrangements all changed at specific chassis number points. Correct identification is essential when ordering, as the tanks, sender units, and seals are not interchangeable between the two designs.
6½-Gallon Tank
The 6½-gallon tank covered the majority of Midget production, fitted from the start of 1275cc production through to chassis number GAN5-105500 (approximately 1971), and then again from chassis number GAN6-154101 to GAN6-182000 on early 1500 production. This tank uses a sender unit with a cork seal, secured by six screws through a flange. Reproduction tanks of this specification are available ready for fitting.
7-Gallon Tank (Later 1500)
From chassis number GAN6-182001 (1976) onward, a revised tank was introduced for the 1500. This later tank has a 7-gallon capacity and uses a sender unit with a rubber seal, secured by a locking ring that twists onto the tank aperture rather than being screwed. The change was driven by the increased fuel consumption of the Triumph engine relative to the 1275cc and the desire to maintain comparable touring range. Reproduction 7-gallon tanks are available for owners restoring or upgrading later 1500s.
Filler Cap
The original non-locking filler cap was used on earlier cars. A 1970s-style locking filler cap provides security against fuel theft. Several aftermarket alternatives are available including a stainless steel design, an RV8-style cap, an imitation quick-release cap, and a genuine quick-release cap (which requires a threaded collar to be fitted to the filler neck). The filler pipe connects the external filler neck to the tank via a connector and rubber hose, sealed to the body panel by a filler neck seal. Renewing the filler neck seal when fitting a new tank prevents fuel odour and potential leakage into the boot.
Sender Units
Three sender unit types were used across production. The earliest type, used on small-bore Midgets up to chassis number GAN4-60459, has a cork seal with screw fixings.
The second type, also using a cork seal with screw fixings, was fitted from GAN4-60460 (start of the 1275cc Mk3) through to GAN5-105500. The third type, fitted from GAN6-182001 onward with the 7-gallon tank, uses a rubber seal with a locking ring rather than screws. The sender harness is routed through a grommet in the boot floor.
Sender Unit Calibration
The sender unit calibration must match the dashboard fuel gauge to provide an accurate reading. The gauge and sender are a matched pair, fitting a sender from a different production period to a gauge from another may result in inaccurate fuel level readings. The chassis number determines the correct sender to order.
Tank Mounting and Rubber Strips
The tank sits on rubber mounting strips (two short and two long) on the boot floor, secured from beneath by six nuts with shakeproof and plain washers on studs welded to the boot floor. A tank fitting kit containing all the mounting hardware, seals, and strips is available for each tank type. A foam seal between the tank and boot floor prevents chafing and moisture ingress. A drain plug and washer at the base of the tank allow the fuel to be drained for storage or maintenance.