Starting Carburettor

Hello and Hoppy New Year to all, We have just installed the carbs on the 150 and there is a pipe that runs fron the bottom of the starting carb to the bottom of the intake manifold. There are four studs at the bottom with a outlet hole. We are missing the connecting pieces. Can anyone tell me what is on the end of the of the u shape pipe and part #'s that runs from the starting carb to the bottom of the intake manifold and also the part #'s for the attaching plate. I could not find anything in the spares book. - Thanks, Skip Smith

I just had a look at my engine (which is out of the car), and the plate has the starting carburettor pipe and another pipe attached to it. I think the other pipe is the vacuum line to the reservior. Look on pages 25 and 26 of the parts catalogue, I think the parts you need are "FLANGE ASSEMBLY FOR ATTACHMENT OF VACUUM PIPE TO BRAKE SERVO" and "STARTING PIPE BETWEEN FLANGE ON INLET MANIFOLD AND CARBURETTOR" - regards, Mike Morrin

Hi Skip & all -- for my Mk IX, built in the same era as your XK150, the Spare Parts Catalogue lists in the Cylinder Head section on p/21 (with pics on Plate 5, p/25): C.14652, L.H. Manifold Starting Pipe Assembly, #69 on Plate 5, with three tubes to front of inlet manifold C.14653, R.H. Manifold Starting Pipe Assembly, #70 on Plate 5, with three tubes to rear of inlet manifold C.14661, Starting Pipe Assembly from Manifold Pipes to Carburretor, #71 on Plate 5 (connection from Starting Carburettor on front HD6 to:) C.14683, Neoprene Tube Connecting Manifold and Carburettor Starting Pipes, #72 on Plate 5 Skip, especially of your XK150 is a 3.8 litre (as all Mk IX were), these should work. I hope this helps -- Larry Martz

Skip, I can't remember if the '150 is the same as the '120 in this department but having just put my 120 engine together I had some trouble obtaining the non-blow-back valve and spring that fits inside the starting carb tube at the manifold end. It was eventually supllied by XK People in the UK, tele no 44 1203 695969. Fax 695968 - Roger Learmonth

Larry, Roger, and Mike, Thanks for the starting carb info. - Regards, Skip Smith

Hi, Well, I worked in the garage for a hour tonight and finished the head except for the tach shaft seal and "O" rings. I am going to need new hoses, thermostat etc., so I am making a list of things I will need for final assembly. I cleaned up the intake manifold tonight and investigated the starting carb that has been disconnected for more than 12 years. I took the wires off and cleaned the terminals and put a little Vaseline on them to help protect them from corrosion. I then used my little jumper wires to test the electric coil @ the battery and guess what ? It worked.. I then pulled the needle cover and I do not understand it from there... the needle is tapered and it appears that if I push down on it like a primer or (a tickler like my old BSA), it appears like it would block the jet in the bottom, not open it, so I am lost as to how this thing is supposed to work. I can see that there is a flat spring against the adjustment nut for the tapered needle to keep it from moving but I do not know how to adjust the carb... there are two long holes on either side of the carb body !! what are they for? I understand that the electric fuel pump pushes fuel through the banjo bolt into the body of the carb body to the jet (which is fixed), then through the jet hole then I am lost at the needle and its function and adjustment .The fuel stops at the solenoid over the flat valve and when the solenoid is energized it lifts the valve and lets the fuel flow into the bottom of the intake manifold. Is the tube going into the manifold nothing more than a open tube or is there a jet in there too. I have not taken that apart yet and I won't unless there is something there that would need serviced. Any input?? - Edgar Blake, 54' XK 120 DHC "Blanch"

Edgar, There is a good description of the starting carb operation in the manual on page C14. The needle is normally up until the engine starts, then it gets sucked down into the jet and partially leans the mixture. The only adjustment is the nut that limits the needle's travel into the jet. Down is leaner, up is richer. The side holes are the air intake. The solenoid valve should have a very weak cone shaped coil spring to hold it closed. The tube into the manifold is nothing more than a tube, but there is an anti-backfire valve under the manifold which you might want to clean. If your starting carb has been non-functional for 12 years there might be gunky deposits inside the jet region and maybe some carb cleaner might be in order. Be careful undoing those banjo bolts if they are corroded, you might bust the carb body. Guess how I know. - Rob Reilly

Thank you Rob, I'll disassemble the back fire valve and have a look. I think I have a good understanding as to how it works now. I found a old manual, unmarked, with a green cardboard cover with brass binder bolts in our home library. It said to adjust when the engine is at running temp and richen until the engine becomes uneven then back off slightly. - Edgar W. Blake

Been to the same position in life.... The solenoid of the ASC when it's "Off" closes of an aperture which is connected into the head assembly. When it opens, which you know it will as you've seen the solenoid solenoiding) an auxilliary supply of fuel/air which effectively bypasses the main carbs is pulled into the engine. The tickler valve is preset to one ratio as its only prpose is to get the engine running at a fast idle. On my Mk V I found that the car was running far too rich due to the time taken for the thermo switch to cut off power to the solenoid and hence reducing the fuel supply so I have installed a manual shut off switch. At the same time I installed a fuel pump shut off switch to allow the ignition circuit to be on without the pump going like crazy when I didn't want a fuel feed to the carbs (like when setting up the timing etc). The tickler valve is sprung against an adjusting nut which has a square anti-rattle wwasher to stop it self-undoing. The springing is simply to get fuel flowing when necessary although I have never needed to tickle.... Adjustment of the plunger is "get the engine running and wind the jet up two turns from the bottom. Next time a start from cold is made, unwind the plunger half a turn uat a time until the engine starts first time every time then leave it well alone. That's the only adjustment recorded for the ASC on Mk V 3.5/2.5L engines. The main carbs are adjusted as follows: Loosen off all the butterfly shaft interlinks: set both butterflies one turn off the individual carburettor stop and then clamp up the shaft so it all works together. Undo the jet cap screw . loosen off the jet clamping nut and wind the jet up into the body till it won't go any further. Slowly do up the clamp screw as you manually slide the piston up an down ... this ensures that the needle remains centred on the jet. Whne it clamped up sensible. wind the jet down 2.5 turns. Repeat on other carb and replace jet adjustibng screw covers. Start engine anmd then when warm adjust idle to about (in my case) 500rpm on the jet. Then tweak the butterfly adjusters to bring it down a tad i.e. the engine is running on minimum fuel input without stalling. - Dick Clements, '51 Mk V 3.5L Saloon in black, '51 Mk V 2.5L Saloon in OEW (almost) The "long holes" that yous ee are probably blanked off at the deep end inside the casting and are usually there for different applications/emgines ... sort of a one-casting-does- three-models- economy-deal for Skinners Union.

Dick's recommended procedure for adjusting the SU's looks to me like a reasonable approximation of the procedure described on C12 in the manual but it takes away the fun of listening to your carbs with a length of garden hose and is likely to leave you with slightly unbalanced running near idle speeds. I recommend the manual procedure. Is there anyone who actually owns a 120 and does not own the Jaguar Service Manual? I'm assuming that the answer to that is "no". If you are an exception, order one today and never leave home without it. One of the things I read about these cars is that although they are unique in many ways, they are actually fairly straightforward mechanically and a reasonably good mechanic WITH A FACTORY SHOP MANUAL can do a competent job maintaining and repairing them. Just don't treat them like any other car. I believe their reputation for being hard to maintain comes from people who don't understand them just screwing them up. (That and just not driving them enough to keep them healthy. It almost seems like they need regular exercise just like we do.) I always have the manual with me just in case I have to depend on someone else to fix something for me - then I can insist that they read and follow the manual. If you don't do all your own work, this is critical. You don't always have the options of either doing it yourself or taking it to a Jaguar specialist. (I've also had to use the manual myself once in a while on the road.) I will add it to the list I am putting together for the "emergency spares kit". Speaking of idle speed, it's kind of a matter of taste. I like to set mine to the point where the red light is just barely glowing a little. I just get a little uncomfortable sitting at a light with the generator light on. Centering the jets can be a trial and error operation because the last little turn of the clamping nut can move the jet slightly off center and you have to back off and do it again. The thing to avoid is overtightening as you just need to put enough pressure on the collar to have the cork gasket compress and keep the main jet from moving around. The first time I disassembled mine, I nearly broke the carb body as some Yank mechanic had apparently used a torque wrench on it trying to stop a fuel leak. There was permatex all over the place. - Bruce Cunningham, '53 XK120 OTS

Bruce: The factory service manual can be a life saver in those away from home emergencies. Due to it's heft, it makes a handy bludgeon for beating the SU fuel pump into reactivation and is yet pliant enough not to leave unsightly, concour point robbing scars. Regards - Bruce Baysinger

I think I prefer the adjustment procedure given in the XK manuals, which is: 1. Get the engine to normal operating temperature. 2. Short circuit the ASC thermostatic switch. 3. "The stop screw should then be so adjusted that the mixture is distinctly rich, that is to say, until the exhaust gasses are seen to be discernably black in colour, but just short of the point where the engine commences to run with noticeable irregularity." - regards, Mike Morrin

THANK YOU, DICK. What a great source of info that we have in this group. My car has always started well, but I always wondered about the proper way to adjust the 'tickler valve'. What a good explanation.I hope to see you in June. I will have the white 51 RHD, OTS, with the Black California license plate on the back. - Larry J, 660636

If you have any questions or comments send e-mail to: ted@jag-lovers.org
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