1975 XJ6 SII ZS with Automatic Choke Help Needed

[bmurphy7369]

After a long illness last summer/fall and a new job this winter that kept me very busy, I finally got the correct Zenith Strombergs and the original water/automatic chokes back from the rebuild shop. When I bought the XJ6C, it had suffered an engine fire and most of the rubber vaccuum lines and fuel lines were burnt badly and removed by a friend. I rebuilt the set that was on the car, but discovered quickly that they weren't correct, they may have been from a TR6, and had the wrong linkage fittings. They were also flooded with water when I neglected to drain the tanks before starting the car.
However, I now have the correct configuration, but after weeks of pouring over the factory parts and repair manuals, I cannot find a diagram that I can work with in replacing the vaccuum lines, reconnecting the auto chokes, etc.
If anyone has a 1975 SII XJ6 that would be willing to share a few photos of the proper fuel/coolant line/vaccuum line layout, I would really appreciate it. I think I can guess at some of these, but am a bit leary after the two engine fires and would feel much better seeing an original and complete installation. My car is the USA Emmission Control type. Also, if anyone is familiar with the water choke systems, where should the coolant be coming from? Since it had been converted to manual choke years ago, there is no indication of the original layout to work from. I can't seem to find any information on this in the Jaguar SII Workshop Manual or any diagrams for the coolant lines to the chokes in the Factory Parts Manual.
Thanks for any help you may be able to give me.

Brian /ubbthreads/images/graemlins/confused.gif

 

[Steve]

I have the automatic water choke and single ZS on my 'B'. It has to be a similar arrangement I would think. I'll take a look and let you know.

 

[bmurphy7369]

Thanks Steve, that will help alot. I'm sure it isn't as complicated as I'm making it, my confidence in my mechanical ability is a bit low right now... don't need any more spontaneous combustion incidents, especially since the garage is underneath the house! I appreciate your reply.

Brian

 

[John S Farrington]

Brian, Haynes publications has an excellent ZS shop manual as well as an SU manual. The ZS manual covers the water choke in detail. They can be made to function but experience has taught me that the best fix for a ZS with the water choke (auto-start) is to convert it to a manual arrangement which is readily available. The auto choke ZS gets overly complicated awhen you go the twin ZS such as on your Jag. The TR7 later models used the twin ZS arrangement with auto choke and it was not a good piece of work. You also will have a hard time finding the dual carburetor auto choke parts. I know that authenticity counts on a restored Jag but I would avoid the auto choke like the plague and go to a dual ZS arrangement with manual choke like the series 2 E Types.

 

[bmurphy7369]

Jack,

I did buy the Hayne's Manual last year, when you recommended it to me. As you probably remember, this has been a project I have been giving alot of thought to for a year or more. When I finally found the correct set of carbs, they came with the automatic chokes. I made the decision when I dropped them off to put the carbs back as original, since my choke cables were badly burned and needed replacement. It probably wasn't the best way to go, but I was sure it wouldn't be too difficult to reconnect all the lines... I didn't check the Haynes yet, so thanks for the advice. I saved some money in not replacing the choke cables, but may end up putting out more in hard to find coolant lines, etc. By the way, if you have scrapped some auto choke Jag 4.2 liter parts, I should ask if you have any of the coolant lines, vaccuum hoses, etc... I still would like that SII door mirror, but will have to wait to check the budget after this project is done. Just drop me a note if you run across any Federal ZS auto choke hoses, etc.

Regards and thanks,

Brian

 

[John S Farrington]

Brian, All of the ZS autochoke parts have long been deep sixed since most of the hardware had problems when it arrived at the shop. I will search over my collection of ZS carbs from previous projects and see if I have an auto choke. If this yeilds anything, I will contribute them to you for only shipping and handling. Ill let you know.

 

[bmurphy7369]

Thanks very much Jack, don't make a special trip. I appreciate your help. I think I am finally making since of the layout. I was using my car's VIN# 2JUF51101 as the reference for different layouts, production point changes, etc. when referring to the Jag Parts and Service Manual on CD-ROM. What looked like the diagram that matched my car always seemed to have a refernce to 8L.2xxxx or 8L.1xxxx onward....... It finally dawned on me that this was the engine number they were referring to, mine being 8L.21446. Now after wiping the grease off of the stamped number on the LH side of the engine, I am breezing through the manuals with ease. Long story short, in my excitement to piece the car back together, I failed to read the Introduction to the Parts Manual which clearly explains how they refernce production point design changes.
I also read a section in the Haynes manual which tipped me off to the possible source of the engine fire issues. Combustible gas forms at a high level with the particular set of Strombergs on my car. If a valve is burnt, the timing/ignition firing is not functioning properly, this will cause a small explosion through the inlet... this is exactly what I am seeing from the port on the rear carb. This may be being made worse by the fact that the prior owner had removed the air pump belt and most of the emmision vaaccum lines to the manifold, air cleaner and the charcoal cannister. I think a compression test followed by an ignition/timing check to rule out the internal fire issue stated above should be performed prior to any other running of the engine.. When I fired up the car three or four evenings ago with the new carbs I saw that same flash and heard the pop out of the rear carb. No fire this time, but that didn't seem normal. I'd appreciate any thoughts or advice you may have as to which direction I should take before replacing vaccuum lines and tracking down expensive NOS emmisions parts/hoses that may just be wasted to another fire under the hood.

Thanks again,

Brian

 

[John S Farrington]

Run the compression check before you do anything else. Also prior to reinstalling the spark plugs, check the spark plug wires to have the right firing order. If you have a mistake on the firing order of the cylinders, you can have fire coming out or the intake manifold as well. Go the the Haynes manual and establish correct firing order. Cylinder 1 is the rear-most cylinder and the distributor rotates counter clockwise.

 

[Dave Russell]

Re: 1975 XJ6 SII ZS with Automatic Choke Help Need

[ QUOTE ]
the Haynes manual which tipped me off to the possible source of the engine fire issues. Combustible gas forms at a high level with the particular set of Strombergs on my car. If a valve is burnt, the timing/ignition firing is not functioning properly, this will cause a small explosion through the inlet... this is exactly what I am seeing from the port on the rear carb. This may be being made worse by the fact that the prior owner had removed the -- air cleaner. -- I saw that same flash and heard the pop out of the rear carb. No fire this time, but that didn't seem normal.
Brian

[/ QUOTE ]

I hope I'm not preaching to the choir:
Never start an engine with the air cleaners removed. If you are going to do it anyway, have a good fire extinguisher close by & stay clear of the engine compartment. A pop back can blow burning fuel all over the engine compartment. It happens more times than you can imagine. A secondary benefit of an air cleaner is that it serves as a flame arrestor. Even boats which don't have an air cleaner have a screen (flame arrestor) on the intake to prevent such mishaps.

I have had two engine fires before I learned, & personally know of two cases where someone was priming a dry carb by pouring gas into it as starting was attempted. Lean mixtures will frequently pop back even if nothing else is wrong with the engine. The lean pop back covered the persons with flaming gasoline. One had minor burns, the other, major burns of most of his upper body. These are probably extreme cases, but it only takes a few seconds to put the air cleaner back on before attempting a start.
D

 

[John S Farrington]

Re: 1975 XJ6 SII ZS with Automatic Choke Help Need

Dave, I respect your advice on the probability of an engine fire from a backfire with the air cleaners removed. However in the case of SU or ZS carburetors your advice cannot be practical. The only way to fine tune and adjust the British style side draft carb is with the air cleaners off. In order to balance multiple carburetors of this type, you must have access to the exposed throats (venturi/dash pot areas) of the carburetors. The manometer measurement or the hose-to-the-ear is mandatory and requires this. In addition to this critical adjustment, there are many other reasons why I want to observe the dash pots operating in the carburetor dynamic situation. I cannot come up with any technique that would circumvent direct access to the variable throat in the operational situation. Your advice is appropriate for a carburetor that is being brought on line initially but fine tuning mandates that the air cleaners be removed. In the case of "priming the carburetor with raw gas" for start up: don't do it. That is a dangerous practice. Get an aerosol can of starter fluid (ether) and judiciously use small quantities to aid dry start ups. That is very effective and presents no problem if the duration of the shots is small.

 

[Dave Russell]

Re: 1975 XJ6 SII ZS with Automatic Choke Help Need

Jack,
I was refering primarily to "dry" starts. Like I said, keep a fire extinguisher handy.

There are other ways to check sync & piston (air valve) position. I have the 100M air box on my Healey. Because this is so hard to remove, it stays on, with no chance of getting at the carb intake. I have had reasonably good results by backing off the slow idle screws until they just clamp a thin piece of paper & then advancing them equally. Actual sync & operation can be observed by placing an extension in the tops of the damper cylinders & observing & comparing the actual height of the pistons under various conditions. My prefered method. To me, sync at part throttle & beyond, is more important than idle sync.

Maybe not "good enough" for a Jag, but OK for the lesser cars?

Regards,
D

 

[bmurphy7369]

Re: 1975 XJ6 SII ZS with Automatic Choke Help Need

I always had reservations about not having the air cleaner on the car, however, I wanted to observe the piston action while bringing the idle up. The point at which I install the air cleaner is when I begin fine tuning which requires the vaccuum hoses that connect to the air cleaner to be attached. The only damage that has been done to the car (fire) resulted from the paper of the air cleaner catching fire and being unable to access it quickly as it burned inside the closed cleaner housing. I agree with you Dave, about the danger, but I remedy this, as Jack said, by using only small amounts of starting fluid and standing out of the line of "fire" of the two air intake ports on the carb... The last reason for leaving the cleaner housing off is simply that it allows ample room to work around the carbs. While it is on the car, it is nearly impossible to tighten a hose clamp or manipulate a screwdriver around the cramped area. Good advice, and I am reminded of how quickly things may go severly wrong by your post. Thanks much for the sage advice.

Brian