1974 Jaguar



November, 23, 2008 AT 10:07 PM

Engine Mechanical problem
1974 Other Jaguar Models V12 Two Wheel Drive Automatic 50,000 miles

Hi there from Australia
I have recently aquired a 74 daimler double six and im having a few issues trying to get it to run.
The old girl was owned by an older english gentleman and he bought it new, drove it for 50,000 KM's and when the battery went flat (activating the central locking kit) he never drove it again. Still has running in oil!
But regardless everything was in good condition when I opened the bonnet except for the vacuum hoses were slightly perished. None the less I have replaced all of them, the spark plugs, and leads and originally I had no power from the coil. Simply I jus ran a direct line to the coil temporarily. My issue is that when I turn it over it will run very lumpily and will not rev, rather backfire. But I have had the carbies off and all of which had stuck needles (float chamber needles) so I cleaned the carbs and left everything factory except replacing the needles obviously. But the problem now lies that on the r/h side bank it runs smooth without a problem. On the left side it misses but is still firing on each individual cylinder. Seems almost as if the timing is out. Strangely when its running it backfires out of the gulp valve pipe that returns to the air filter.

Another strange tidbit is that the vacuum hose was missing off the dizzy, but when I went to replace it mine seems two have a two way diaphragm. It looks the same as a normal retard one but mine does both advance and retard, could this cause any issues?

I keep coming up with dead ends as to where to go.
Hopefully u can help me nut out this problem



5 Answers



November, 23, 2008 AT 10:42 PM

Hi there,

What oil did you put in the dash pots on the carbies, if it is to heavy you will have this problem, also the main needle must be centralized correctly. The vac advance and retard will not affect the idle quality, I would be checking for a vacuum leak on the problem bank first, start here,

Mark (mhpautos)

P.S. Where in Oz are you, I may be able to direct you to a good Jag man.



November, 24, 2008 AT 3:06 PM

Hi there.
I was told by a jag enthusiast to run ATF in the dash pots. Unsure if this is actually correct though as the repair manual suggests that regular engine oil should be used. I was told to fill up the piston sleeve only where the removable slide operates in the dash pot but when this was done to move the actual pistons in the carbs were very difficult. Last night I completely drained all fluid but had no chance to test.

As far as I can see there are no manifold hoses disconnected, though the air filter boxes are disconnected. I wasnt sure if this could affect it as the air boxes have float chamber balancers on them. Is there any tests I can run to devise where the issue might be?

As for where I live its a island south of australia called tasmania, and the suburb is Hobart. Unsure if u are from here also.

If anyone knows the figures of how many daimler double sixes still live in australia i'd be keen to find out, only the carburetted ones of course.



November, 24, 2008 AT 3:42 PM

HI there,

I am in Aust, In Traralgon Southern Vic.I was in old Hobart town a few weeks ago on holidays. There is a special light dash pot oil you can get but it is a bit hard to locate, trans oil is a bit heavy, I would look on line for SU carby oils. I would get that side of things sorted first before you go looking further, as it is critical to get the carbies sorted first.

Mark (mhpautos)



November, 24, 2008 AT 3:58 PM

Thanx mate ill try that too.

I know the brake booster lines were slighlty perished around the actual joints but I wouldnt imagine that'd kill it too much hey. Perhaps if all else fails I should go back to basics and block all but the necessary vacuum hoses etc.

P.S how should the diaphragm be hooked up on the dizzy as it has both advance and retard hose options, but to make either one work they both individually suck to do thier action, therfore if both are hooked up it cant do either operation cause it will try to advance and retard at the same time. I was reading in the manual that there was some form of switch that controls such things but mine is an australian delivered and doesnt have that option. The only way I could think is that my left bank hooks up to the advance and right to retard or vice versa?

Sorry for all the b/s but im racking my brain with this as im not used to this type of engine.

Mybe you know someone on this site who has digrams to help with the vacuum lines as my repair manual doesnt explain it very well



November, 24, 2008 AT 4:12 PM

I do a few 12's but there all EFI, and info is a bit hard to come by for the S U version, , as for the vacuum for the dist, I will have to do a bit of home work on that for you, I am just going to have a re think on your problem again and I will get back to you with my thoughts.


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