Hi

I'm trying to help a member of Jaguar Club of Denmark. He has found an XJ12 from 1982. It has the Lucas ignition amp and is thereby HE as it should be, but it also has the cloth hanger style fuel rail I (and he) thought belongs to the PreHE.
I have tried to find info about when the U-shaped fuel rail was introduced, but didn't succeed. It seems there is a recall for replacing the old type fuel rail in 1985, but the question is if a 1982 can be born with the round tube rail ?
And yes, I know this is not the XJ section, but this is where the V12 knowledge is...

 

Leo
I have seen a factory 1983 US spec XJS V12 with a round fuel rail (rather like the familiar square section HE rail; but round) this was not like the pre-HE coat hanger shape. Bizarrely, the factory position for FPR for this rail was on the back of the throttle capstan! The recall was for the round shape I mentioned (not the pre-HE coat hanger shape) to change it to the square section one, and also relocate the position of the FPR to B bank as we now are familiar with it.
Have you a photo of the rail in question, as it might be the type I saw, maybe?

 

Thanks. No photos, but I will ask for one !

BR Leo

 

 

Leo,

As Greg said, that's more like an HE rail but round. It's not a typical pre-HE rail. Maybe it's aftermarket or something Jaguar fitted when they had supply problems?.

Sorry, I can't help further

Paul

 

My May 1984 XJ12 parts catalog shows the round/tube fuel rail for the HE engine.

I am 99% sure the square section rail was originally a retrofit as per a factory recall as has been mentioned. At some point it (the square section rail) was incorporated into regular production and used on the assembly line.

I have a load of TSBs and I'm sure this issue it was explained....but I'm not when I'll have the time to sift thru them.

Cheers
DD

 

I found this online for early HE engines.

 

That settles it. Thanks all !

 

Paul, Doug
I know, for a fact, that the HEs were first fitted with the rail as in Leo's photo. It was subject to a recall in 1984, and replaced by the square rail as a factory paid for safety change. You can also see the FPR in its odd back of tower position JAL's diagram.

 

Beautiful! Love the pictures. Always find the back of these cars, years just gorgeous.

Lucielle

 

I found these words from Roger Bywater, written 15 years ago back in 2006:

My recollection is that the original D Jetronic fuel rails were made that way on advice from Bosch who favoured two full loop rails each with its own regulator as the best way of avoiding any biased flow. We were not totally convinced and started experiments with a larger diameter single loop/single regulator setup in about 1977.

This was adopted for the 10:1 compression V12 with 6CU EFI for 1980 with a single pressure regulator now linked to manifold vacuum to provide constant pressure drop across the injectors at all loads. The regulator was mounted low in the engine valley behind the throttle tower and simple hose clamps and fittings were employed. The same arrangement carried over to the HE when it was introduced in 1981.

Originally the single loop rail was made in two parts joined across the ends by short hoses but, after a few under-bonnet fires occurring at start up, there was a recall to change to a one piece rail eliminating the end hoses as a source of leakage. It was thought that vapour from any slight leak would build up in the valley and permeate into the distributor where the first spark would, in the right (?) circumstances, initiate the fire, often splitting the cap as it did so.

Sadly the incidence of fires did not abate and there was eventually a major recall in about 1983 when all cars were fitted with the now familiar square fuel rail, incoming and outgoing regulators and vented distributor cap. Leakage within the valley was now eliminated but I personally was never convinced about the cap venting because the fire risk only developed whilst standing and that fatal first spark occurred before any venting flow took place. There was a theory that crankcase fumes might have been part of the story but again that does not seem very plausible to me. I suspect that Jaguar just decided to cover all eventualities and make sure the problem was killed � which was indeed the case.

The exact purpose of the incoming regulator has never been made clear. For a long time I assumed that it was there to prevent pump noise transmitting through the car and also to prevent vapour lock occurring in the fuel feed line. With further thought I suspect that it also works as a sort of fire door, isolating the fuel rail from the feed pipe so that any seepage that might take place would be limited to the contents of the rail and not added to by vapourisation in the feed pipe. It should be remembered that fuel temperatures can easily exceed 60C on a hot day with a near empty tank.

The facelift cars had a new more modern style of fuel rail with more secure connection methods so the potential for leakage was reduced and the hot fuel handling was improved. It therefore became possible to dispense with the fuel cooler and the incoming regulator.

In the circumstances I think it is most inadvisable to remove the incoming regulator. ...

 

Paul,

Fasinating read, thank you,.

OOPS on the Incoming, no got on any of mine and NO fires.

BUT

We are ALL rather obsessed with our fuel hoses????, or am I deluded??

Some snaps I see on here at times from members that are doing something in the "V" and the fuel hoses look ORIGINAL and so sad. Maybe show and shine is more important to some, or I am just plain OLD.

5 years is my MAX for fuel hoses on ANY car, Jag or normal.