Opeless Opus,help needed with vacuum info
#1 Opeless Opus,help needed with vacuum info
Can anyone do me a favour please? I have a seris 1 XJ12 in stock original condition except that the hopeless opus was replaced before I bought the car with the SNG Barratt system. The car runs superby well but just feels a bit uneven under load. It may be a faulty plug breaking down but, whilst looking at the engine I note that the vacuum retard capsule on the Distributor is not connected. Moreover, I cannot even see where the vaccum pipe to it would originate. In all my books there is no indication of where the vaccum is picked up. I assume, firstly that a V12 E on strombergs like mine will be very similar, so if someone could take a look, or e mail me an image I would be very grateful, and secondly I am assuming also that the vaccum retard is still valid on an SNGB modified system? Thanks in advance as its a bit of a mystery and I am sure it will run better if its meant to be connected!
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#2
Andrew
I don't know if you have resolved this yet, but anyway.
The take-off for the vacuum retard on the V12 E is from the rear left carb. There is a short pipe from the bottom side of the carb to manifold mounting flange to which the vacuum line to the distributor is attached.
The vacuum retard is an emissions thing which gives faster engine warm up. Many e-type owners disconnect this and plug the vacuum line. A retarded engine runs hotter which is not what you want with a Jag V12.
Later cars than mine and US exports had a thermo vacuum solenoid switch thingy fitted in the coolant rail at the back side of the "A" bank head. I don't know the details of this but I believe that, among other things, it had some control over the vacuum retard. Yours being a later vehicle may well have some such device.
I don't think the vacuum retard will have any affect on the car running "uneven" under load.
You will have to ask SNG about their system.
You could ask the question on the XJ Forum of Jag Lovers if you have not already done so.
Pete
I don't know if you have resolved this yet, but anyway.
The take-off for the vacuum retard on the V12 E is from the rear left carb. There is a short pipe from the bottom side of the carb to manifold mounting flange to which the vacuum line to the distributor is attached.
The vacuum retard is an emissions thing which gives faster engine warm up. Many e-type owners disconnect this and plug the vacuum line. A retarded engine runs hotter which is not what you want with a Jag V12.
Later cars than mine and US exports had a thermo vacuum solenoid switch thingy fitted in the coolant rail at the back side of the "A" bank head. I don't know the details of this but I believe that, among other things, it had some control over the vacuum retard. Yours being a later vehicle may well have some such device.
I don't think the vacuum retard will have any affect on the car running "uneven" under load.
You will have to ask SNG about their system.
You could ask the question on the XJ Forum of Jag Lovers if you have not already done so.
Pete
Pete
'71 S3 2+2
'71 S3 2+2
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#3
Hi there, thanks for the reponse. What I have discovered is that the X12 series one for UK supply did not have the vacuum advance connected. I found the vaccum pip under the rear carburretor and this is blanked off with a rubber bung which looks like it was done at the factory. To be honest the car runs so well other than this slight hesitation I suspect its either a vacuum pipe on the carbs weakening off the mixture at revs or a plug breaking down. Thankyou very much for the input though.
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