SU electric fuel pumps have been fitted to British cars for decades, and the different types are easy to confuse. Here is how the main single and dual pumps compare, based on the figures in the SU workshop manual. Use it to check you have the right pump for your car, and that it's mounted where it can do its job.
Single pump specifications
| Pump | Voltage | Capacity | Pipe bore | Maximum line pressure |
|---|---|---|---|---|
| L type | 12V | 8 gal/hr | 0.25in | 1.5 lb/in² |
| HP type | 12V | 7 gal/hr | 0.25in | 2 – 3.8 lb/in² |
| AUF 200 / AZX 1200 | 13.5V | 7 gal/hr | 0.25in | 2.7 lb/in² |
| AUF 300 / AZX 1300 | 13.5V | 15 gal/hr | 0.312in | 2.7 / 3.8 lb/in² |
The AUF 200 and AUF 300 have a minimum starting voltage of 9.5V with standard coils, drawing 1.5A at that voltage. Some pumps use alternative coils with a lower minimum starting voltage.
Which pump is which?
L type
A suction pump designed to be mounted close to the engine, in the engine bay. Its low pressure makes it unsuitable for pushing fuel a long way.
HP type
A higher-pressure pump designed to be mounted near the fuel tank at the rear of the car. Mounting it there also keeps it away from engine heat, which helps prevent fuel vaporising.
AUF 200 / AZX 1200
The smaller of the later SU pumps. It's a compact high-pressure unit with inlet and outlet connections that rotate through 210° to make fitting easier. It was usually 12V but also made in 6V and 24V versions, plus a low-pressure version. It suits cars in the low to middle power range.
AUF 300 / AZX 1300
A high-capacity development of the AUF 200. The body adds a flow-smoothing diaphragm on the outlet and an air bottle on the inlet, which damp pressure pulses and increase output. It delivers 15 gal/hr through a larger 0.312in pipe. Installation limits are an 18in maximum suction lift from the bottom of the tank to the pump, and a delivery head of up to 48in above or 6in below the pump to the carburettor.
Dual pumps: AUF 400 and AUF 500
AUF 400 / AZX 1400 is essentially two AUF 300 pumps on a common body, with a shared inlet and outlet. It delivers up to 136 litres (30 gallons) per hour for high-demand engines.
AUF 500 / AZX 1500 is built the same way but works as two separate pumps with two inlets, for cars with twin tanks or a main and reserve supply. Each coil has its own terminal, normally wired through a change-over switch, and both sides feed a single outlet.
Points or electronic?
Original SU pumps use tungsten contact points to switch the coil. They work well but the points eventually wear or burn, which is the most common cause of a pump that stops and needs a tap to restart. Electronic versions replace the points with a solid-state switch and need no adjustment. They are also built for a specific polarity, so make sure you order positive or negative earth to match your car, or a dual-polarity pump.
- Browse SU electric fuel pumps, including the AUA 25 LP pump and AUF 214 HP pump (dual polarity)
- Overhaul an existing points pump with an EPK 200 LP or EPK 300 HP repair kit
- Or send it to us for a full pump refurbishment
Fit a filter
Whichever pump you run, dirt is its enemy — a speck under a valve disc stops the pump delivering. Fit an inline fuel filter between the tank and pump, sized to match your fuel line.
Not sure which pump your car should have? Use Find My Kit or ask us.