(Fwd) (Fwd) Re: [xj-s] Vacuum Timer circuit

Roger Bywater’s comments on vacuum advance systems.

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Yes, well I can understand that there could be a problem but don’t be too
hard on Jaguar, I’ve seen much more complex systems on Hondas and things.

Where ball bearings and things have been stuffed up pipes it is obvious
someone has been bodging. (Having said that, and strictly off the record,
it is not unknown for a crafty emissions engineer to quietly block a pipe
off to help get through an emission certification test)

After the HE was introduced, in 1982 Jaguar produced a supplement
(Publication AKM 3455/S1 - almost certainly discontinued but we do have a
copy) to the workshop manual which had full descriptions of the vacuum
systems used on European and Federal cars including detailed explanations
of how they worked. It takes a bit of concentration to follow but the basic
info is there. I am pretty sure that the UK cars stayed more or less the
same up until Marelli whilst any later changes for other markets are likely
to be minor variations of the same theme.

I cannot offer any help for the older cars but I do recall that there were
a lot of variations for different markets and I doubt if there is anyone
who knows them all. Quite lot of cars had retard capsules in the early
days, in fact I think you will find all carb V12s had them. I may be wrong
but I think the vacuum systems on the pre-HE cars were not all that
complicated so shouldn’t be too difficult to sort out.

Roger.From: Roger Bywater 101351.1414@compuserve.com

I might add that I HAVE AKM 3455/S1 – it’s what I’ve been calling
the “Supplement to the Repair Operation Manual” – and I find it not
very helpful in vacuum advance schemes. In fact, the scheme on my
own car is not listed; I must refer to the Haynes manual to find a
schematic of the vacuum system on the US-spec '83.

– Kirbert | If anything is to be accomplished,
| some rules must be broken.
| - Palm’s Postulate