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Every petrol engine needs a helping hand to wake up on a cold morning. Today we take chokes, automatic enrichment devices, and electronic wizardry for granted, but in the early days of motoring, things were rather more hands-on. Before carburettors had starter jets and proper cold-start systems, drivers relied on primitive priming cocks to squirt a little fuel directly into the cylinders. Then, somewhere between those crude methods and the modern choke, came a clever invention that became legendary in its own right: the Ki-Gass primer pump.
Simple in principle yet vital in practice, the Ki-Gass could make the difference between a reluctant engine and a smooth start. But without proper maintenance things could go wrong—as owners of everything from Bugattis to tractors discovered—the results could range from wasted fuel to the ever-popular “petrol on the knee”
The Ki-Gass company began life in 1924 under the more prosaic name Key Brass, later rebranded Kibraz before finally settling on the name that would become famous. Based at 15 Carrington Mews, London W1, the firm quickly earned a reputation for its ingenious priming devices. Their “Easy Starter” injector was used on such exalted machinery as the Bugatti Type 35 and the Vauxhall 30/98, while the company’s blowlamps were common workshop tools.
But it was the hand-operated fuel priming pump that put Ki-Gass on the map. These sturdy brass devices were fitted to an astonishing range of vehicles: Bentleys, high-performance sports cars, agricultural tractors, trucks, tanks, and even aircraft. In fact, during the Second World War, Ki-Gass pumps were used in Spitfires, Hurricanes, and virtually every other British warplane. For many years if it had a petrol or diesel engine , there is a good chance Ki-Gass had a hand in starting it.
By 1945, the firm had moved to Leamington Spa and eventually expanded into automotive components, electronics, and plastic mouldings. Yet for enthusiasts today, the Ki-Gass name remains synonymous with those iconic primer pumps.
The Ki-Gass pump is delightfully straightforward. Fuel is drawn from a feed pipe and delivered to an atomiser in the inlet manifold. Pulling back the pump handle creates suction inside the body; pushing it down forces fuel through the outlet valve and into the intake mabifold, richening the mixture just enough for a cold start.
Interestingly, the pump doesn’t use a piston or a conventional seal. Instead, careful tolerances and simple one-way valves do the job. It’s robust, reliable—until, of course, it isn’t.
Ki-Gass priming pump with T-handle
Ki-Gass pumps are tough but not indestructible, and they have a couple of well-known bad habits:
Our rebuild kits use an improved graphite/PTFE impregnated cord. Our current version of the Ki-Gass pump has an acetal tip and a discreet Nitrile O-ring seal fitted in a groove machined inside the top clamping nut to to ensure a proper seal.
The result is a Ki-Gass that works as intended—without the smell of petrol following you everywhere.
Enthusiasts may spot two main types of Ki-Gass pump: the early version, with inlet and outlet forming a Y-shape, and the later model with parallel valves, shorter versions were also available. Different handles were also fitted—some wore study T-handles, others simpler knobs—but the operation remained essentially the same.
It’s easy to overlook the Ki-Gass pump. A small brass plunger tucked discreetly on the dash or bulkhead, it lacks the glamour of a polished carburettor or the mechanical drama of a magneto. Yet this modest gadget was once indispensable. A tired or poorly maintained Ki-Gass can be more hindrance than help.
Properly rebuilt and correctly used, however, the Ki-Gass is a delight. It’s a direct connection to an era when drivers had to prime, crank, and coax their engines into life, rather than simply pressing a starter button. For the vintage enthusiast, it’s a reminder that sometimes the smallest components have the biggest stories to tell.
Our rebuild kits include the required length of graphite/PTFE impregnated cord gland seal, 2 shorter springs and 2 longer springs - included to deal with inlet and outlet spring housing design variations and 2 brass ball-bearings
Ki-Gass hand primer pump with repair kit
Fully dismantled view for reference
NOTE - it is not necessary to remove the valve part (casting with arrows) from the barrel for servicing. It is secured with a ring of solder and needs “sweating” off after precautions to remove all petrol.
Remove the old compacted seal with a suitable pick tool and clean surfaces. Coil in the new length of graphite impregnated cord in a clockwise direction - direction of tightening.
Screw down to compress the seal. Aim for approx 5mm of exposed thread when the part is snug. This is to allow for future tightening as the seal settles and compresses. Trim length of seal as needed. Secure locking ring. Do not over-tighten.
NOTE - Vintage Ki-Gass pumps rely solely on the impregnated cord as a sealing gland. Our current version of the Ki-Gass Primer Pump has a secondary Nitrile O-ring seal fitted in the groove shown here, to act as a secondary seal.
NOTE - it is not necessary to remove the valve cast part from the barrel for servicing (soldered).
After removing the copper fuel line female connectors (not shown), the end unions can be removed.
< 5/16” UNF male/male >
Clean the seats and check for blockages. For later type (shown) it is recommended to try the shorter pair of springs first and check pump action. If valves are not sealing correctly, then use the longer pair of springs.
For the early type (with Y-shaped valve inlet/outlet) Most commonly a short spring is required on the inlet of the pump and a long spring on the outlet.
IMPORTANT - Both unions have a cone seat for solder nipple connection at one end. At the other end, one union has a square cut socket to receive the base of a spring, the other union has a bull-nose recess to receive a brass ball bearing
Replacement End Fittings
Our rebuild kits include the required length of graphite/PTFE impregnated cord gland seal, 2 shorter springs and 2 longer springs - included to deal with inlet and outlet spring housing design variations and 2 brass ball-bearings
Ki-Gass hand primer pump with repair kit
Remove the old compacted seal and clean surfaces. Coil in the new length of graphite impregnated cord in a clockwise direction. The seal fits between the sliding brass ring, and the alloy threaded collar. Note - if the cap/knob needs to be removed, it is usually secured with pins.
Screw down to compress the seal.
Aim for a few millimetres of between the hex nut and the knurled lock ring when the part is snug. This is to allow for future tightening as the seal settles and compresses. Trim length of seal as needed. Secure locking ring. Do not over-tighten.
After removing the copper fuel line female connectors (not shown), the end unions can be removed.
<5/16” UNF male/male>
Clean the seats and check for blockages.
For the early type (shown) most commonly a short spring is required on the inlet of the pump and a long spring is required on the outlet side.
IMPORTANT - Both unions have a cone seat for solder nipple connection at one end. At the other end, one union has a square cut socket to receive the base of a spring, the other union has a bull-nose recess to receive a brass ball bearing
All articles and guides are provided only for the interest of classic and vintage car owners. A certain level of mechanical and electrical knowledge will be required in undertaking work as described in these articles, and anyone unsure of their abilities is advised to seek professional assistance.
SVC (Vintage Supplies Ltd) cannot be held responsible for any breakages and injuries that may occur, while working on a vehicle following any guides provided. With older vehicles being exempt from MOT checks, responsibility for vehicle safety and legality rests entirely with the owner.
