Well, Con - but do they click while cranking?
The fuel pressure regulator is connected to manifold vacuum - usually using the spigot on the top of the manifold. The dist vacuum hose usually goes to the throttle body - and on ‘European’ versions ; this connection serves other vacuum users, like the AC, by ‘T’ connections. Which explains some loose hose ends…?
In any case; unconnected vacuum hoses/spigots should be plugged/capped until they find a home. While various vacuum diagrams are presented in the Archives - but they vary with equipment level model year and market…so what’s yours…?
The bare minimum is; dist and AC - and brakes, of course. As David imply, if there are two spigots on the throttle body; one has manifold vacuum in idle. The other then has ‘ported’ vacuum used on US ignition - and has no/very little vacuum in idle. However, any spigot on the manifold implicitly has manifold vacuum - but the spigot underneath is a drain as mentioned…
In any case; it’s important to verify what sort of vacuum is delivered. ‘Ported’ vacuum is only used for the US dist - all other users use ‘manifold’ vacuum…
If an engine dies and then won’t start - it is sure relevant, Con…
While hot engine slow dying may have various causes - there is no obvious ones that prevents restarting a cold engine. Engine rpms is basically related to the amount of air the engine is getting.
Typically, as the AAV closes, idle slows - and with insufficient hot idle the engine slowly and smoothly dies. The AAV then, supposedly, opens as it cools - and the engine restarts.
If fuel pressure drops, lack of fuel will gradually slow the engine, but it will usually misfire before dying. With fuel pressure rebuilt - the engine will restart. Gradually increasing fuelling will again slow the engine - but it will show distress, misfiring, before dying.
The CTS plays a vital part in fuelling, it gradually leans out the mixture as engine warms up. If it does not; mixture stays rich - and the engine will gradually overfuel, and may die. Again; a cold engine will restart. If the CTS fails ‘lean’; it has no effect on a hot engine, but cold start may be an issue…
Failed ignition will lead to misfiring, which will slow rpms - but not slowly. There is one combination. The AB14 module is sometimes heat sensitive - and in some cases; as the idle gradually drop during warm-up, AAV action - the ign amp may reach a cut-off point, and the engine suddenly quits.
However, cooled down, the ign amp may recover and the engine starts cold - unless the ign amp decides to call it quits. In which case there is no ignition and no start. ‘Dramming’ the engine will clarify if the ign is working satisfactorily…
There are probably more possible, or impossible permutation - but getting the engine running is first priority…
For the record; you start an xk strictly ‘feet off’ - engine will baulk if gas pedal is used.
xj6 85 Sov Europe (UK/NZ)