Twin Overhead Camshaft
  The Nathan twin overhead camshaft Imp engine fitted with Tecalemit-Jackson fuel injection. The 849cc version gave 98 bhp and 998cc 125 bhp.

The Imp Site

Petrol injection / Fuel injection

The squirts are controlled by little electric solenoids which are in turn controlled by the computer.

A fuel injection system from a Volvo 244 (2.3 ltr) will work on a 1 litre Imp, as Nick Cleak's turbo charged Imp has been testifying for more than 10 years: perfect cold starts and no stalling or rough running when cold.
Fuel injector Sizing Program by Bowling

Chris wrote:

Talking to Peter Harper last week, he told me he was given the task of testing out a Hillman Imp Rootes had converted to Fuel Injection, he was given it to run around in for several months, states he used to cause havoc on the motorways, waited for some high powered car to come past at speed, he waited until they were some distance in front then put his foot down, overtook the car like a bullet and left sufficient turbulence to cause a panic attack. The Imp developed 130 bhp in standard form? The Rapier that had been converted went like a dream, and could not believe it was not put into production. The system was being developed by Tecalemite. Will be making some enquiries to see if the still exist.

MegaSquirt Electronic Fuel Injection: perhaps interesting, though the name may not inspire trust. The site contains the complete hardware and software plans to build your own fuel injection controller. Both the site and the product look neat.

In one and a half seasons, by the end of 1967 John Griffiths, one of the Fraser mechanics had the Imp's power increased from 95 to almost 120bhp. The power came from
• a large-valve high compression cylinder head
• a racing camshaft and
• Tecalemit-Jackson fuel injection.
It could safely rev up to 9,000 rpm.

CCC January 1968 (p. 414-416):
The Player's (John Player and Sons) No. 6 National Rallycross Championship was divided into four areas. One of the southern area points scorers was Dave Lambert in his fuel injection Rallye Imp.

Ron Beswick & Stuart Preacher won in 1974 the Cambrian Rally in a 998cc Hillman Imp PI - petrol injection. All the competition preparation had been done by Skip Brown, a good friend of Ron.

Gerald Stanley has/had a racing G15 which was modified with a Weber Alpha Fuel Injection System.

Mr. Bill Wanderer, 'Mr. Bill', was a legendary figure in the boat racing world. He built slide valve fuel injection for the Imp as well as other engines.

Peter Ware, before he joined Rootes in 1958, worked for Leyland and CAV on fuel injection systems.

Clan, Q516 UHB, for sale in 2009 on the web, Weber alpha injection fuel

Ian Forrest was experimenting with injection


    Tecalemit-Jackson diagram

Truth about injection !. - Car Mechanics 1971, March. - pp. 36-37
"... makers admit that the major improvement comes from better manifolding"
About Lucas P.I. system and Tecalemit-Jackson, not in detail.
Two quotes:

"The TJ system can theoretically be set up for any car - IF you can get manifolds to suit - but in practice you haven't a hope in hell of getting the thing set up decently without extremely expensive bench trials by experts."
"'re still stuck with the practically insuperable obstacle of adjusting the mixture strength."
1. electric pump

The Tecalemit system starts with the electric gear pump, mounted under the floor, and the check-and-bleed valve. This provides basic pressure ...

    mm     The TJ system uses an electric pump (1), which pushes fuel at 25 or 30 psi
2. filter       from a filter (2)
3. a non-return 'check & bleed' valve       through a non-return 'check and bleed' valve (3). From there the petrol goes
4. engine-driven pump

... and the mechanical pump, driven off the crankshaft by a toothed belt, provides the extra pressure needed to fuel the engine.

  mm   to the engine-driven pump (4). When this pump is stationary (i.e., with the ignition switched on, but the engine not turning), fuel passes through it,
5. pulse unit       and a diaphragm valve in the pulse unit (5) is opened by the fuel pressure created by the electric pump.
This valve
6. relief valve unit       permits the fuel to pass through another valve in the relief valve unit (6) and
7. pipe to tank       thence back to the tank via pipe (7).

The valve in the pulse unit (5) requires a fair pressure to open it - enough pressure, in fact, to ensure that fuel runs through the stationary pump and right round the rest of the circuit - along pipe (4). through the control unit (10),

8. equalising valve       and on to the equalising valve (8), which is the last step before
9. rail distributor       the rail distributor (9) and thence the nozzles.
        There isn't enough pressure to open the equalising valve at this slage, but with everything else full of fuel you can consider the system primed.
When the engine starts turning, the pump (4) also begins to revolve. This pump does two things.
From one end it sends out a pulse of fuel along line (13), which closes off one of the valves in the pulse unit (5) and then finds its way into the relief valve and back to the tank. The valve that was closed thus increases the pressure of all the fuel in the operating part of the system. This pressure is now sufficient to open the equalising valve (8), and permits fuel to enter the engine.
10. control unit

Inside the control unit are cams which operate main metering valve and acceleration pump.

  mm   As you rev up, the simple rotor pump at the other end of the engine-driven pump starts working for its living, and puts up the pressure in the main delivery pipe (14) to the control unit (10).
The control unit looks after the flow of fuel reaching the equalising valve. So far as the fuel delivery is concerned, the unit is nothing more than a finely machined fuel tap connected via a series of linkages to the throttle butterflies and your right foot.
11. equalising valve       Also operated by a cam inside the control unit is a diaphragm valve which delivers an extra squirt to the equalising valve along line (11). This pan of the control unit,
12. pipe to the acceleration device of 10.       fed by pipe (12) from between the pulse and relief valves, is known as the acceleration device, since it operates in exactly the same way as the acceleration pump in a fixed-jet carburettor. The object is to provide extra mixture enrichening during the acceleration phase.
13. line to close off one of the valves in 5        
14. main delivery pipe to 10        

The TJ untimed system relies on engine speed and throttle opening to govern the amount of fuel that goes into the engine, with enrichening for acceleration provided by that throttle-operated diaphragm pump. On the face of it, it would seem that a continuous jet of petrol would make for considerable unburnt petrol and therefore high consumption, but in practice it appears that the petrol which squirts into any one manifold while the inlet valve is closed has to hang around in the manifold and eventually gets sucked in and burnt when the valve does open.
This would seem to mean that atomisation isn't as good as it should ideally be with an injection system, but in practice there undoubtedly is a gain in power, and when the equipment is set up correctly, the fuel consumption generally runs out at about the same as an equivalent atmospheric engine.
Tecalemit themselves admit that most of the gain in power comes from having a decent manifold shape, though.


Full rich for cold starts is achieved by a cable opening the fuel valve further. Another cable links unit to throttle butterflies, and must be adjusted to synchronise the take-up.
Fuel flow from the electric pump is checked with a pressure gauge. This governs delivery at tick-over, before the mechanical pump takes over completely.
The only other adjustment is again to see that the butterflies are synchronised. Slow running air is adjusted by screws (arrowed).

The original setting up of the mixture must be left to those with brake testers and the like.

The TJ equipment can be adjusted to the extent that the tickover fuel pressure can be set by a knob which adjusts the tension of one of the valves in the pulse unit. (A voltage control device ensures a steady voltage to, and hence a steady pressure from, the pump.)
The amount metered into the engine by the control unit and the size of the main restrictor in the delivery pipe which controls the flow on full bore, can again only be determined by someone using all the equipment in a good brake-testing shop.

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      Turbo- not that simple! (Sep '98)
      Fuel injection (Dec '98)
      Fuel injection (March '99)

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