XK Engine 4.2L, Fuel Injection,
 Vacuum System Connections

There appears to be no definitive diagram of the vacuum connections of the various versions of the XJ6. Hardly surprising given the number of possible variations. Fuel injection or Carburettors, Air Conditioning or not, European or USA emission regulation requirements, added to the fact that the heater controls were also vacuum operated and not to mention Jaguar / Daimler Series 1,2 & 3 variations. This can be quite confusing to the builder of an XK powered Nostalgia Classic XK120 / 140
 

The Nostalgia Classic Vacuum connections are simple, once you have sorted out the components that need to be connected and their location. Use hose specifically made for vacuum connections for all pipe work. Make sure when routing hoses they are kept as far away from heat sources and rotating parts as possible.  To assist the description the manifold should be viewed with the throttle body on the left.

The major component is the inlet manifold, source of the vacuum that is going to be used by the other components and where all the connections are made.  The "plenum" is a big hollow box that is the bulk of the inlet manifold. The connections are marked "A", "B" "C" & "D" in the diagram . In keeping with the above, there are variations in inlet manifolds as well.  Underneath the manifold you will find a large bore connector. To this connector fits the large bore vacuum pipe from the auxiliary air valve (connection "C"). You may also find 1, possibly 2 small bore connections.  The rear most one (nearest the bulkhead) is likely to foul the steering column in the Nostalgia configuration. it should be pulled out, it is only a press fit. (A pair of "Mole Grips" should do it) and the resulting hole blanked off (a round head screw of approximately the same size as the hole, glued in place with epoxy resin will suffice). The remaining small bore connection "A", is used to connect the distributor, full load switch and the throttle body to the inlet manifold)  On top of the inlet manifold are the remaining connection "B" which connects to the fuel regulator and "D" which connects to the Brake Servo.    

For a printer friendly version of the diagram click here.

 

 

 

 

 

 


The Fuel Regulator is mounted on the fuel rail. It is connected to the inlet manifold by a single vacuum pipe (Connection B). The Haynes manual for the XJ6 shows the vacuum connection routed via a clamp in the fuel rail, but all the engines I've seen have the connection direct to the inlet manifold as shown in the photograph

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