Starting on Choke

[MarkG]

My car starts OK, but won't run for more than about 30 seconds on choke without dying. If I'm driving it on a cold engine, I'm constantly pulling and pushing the choke depending on throttle just to keeep the engine running. It runs fine when warmed up.

I recently had everything on all 4 carbs to bits to check operation and blew through with a high pressure hose. I now understand how the choke should work and there seems no reason for it not to; butterflies open a little and two sets of holes on the choke distribute extra fuel to the first carb and via a pipe a second set of holes to the second carb. I did not dismantle the float chambers though because I did not have spare gaskets to hand. I re-assembled everything, balanced the carbs on tickover and adjusted the mixture. When warm it runs very smooth.

I just wondered what other cars acted like on choke before the engine is fully warmed up since I've never driven another V12.

Mark

[coalboy]

need full choke on mine to start, let run for 5 minutes then push in a notch and set off, no problems with stalling though a little sluggish accelerating at first.
nigel

[D COUPE]

Ican second that. Mine loves the choke till it gets warm then its OK

DC

[AussieEtype]

Mine requires full choke to fire and then to run when cold on the middle position then off when warm - it will not continue to run after firing if left on full choke.

Garry

[MarkG]

That's good to know. Now I know there is something wrong with mine. With the choke fully off, what size is the gap between choke cam and the head of the screw which pushes it? Thanks

[MarkG]

Well I sussed what was wrong. After much head scratching, I realised the carb cam was slightly bent on one side so the screw holding open the choke slipped off as I pulled the choke out. This meant I was getting choke only on 2 carbs and 6 cylinders. No wonder it wouldn't idle properly on choke!

I straightened the cam out using my finger and hey presto. Now idling and driving just fine on choke.

I did spot something else though; a hairline crack in one of the carb bodies. Blowing at the outside with a high pressure line revealed it tracked through into the fuel air mixing chamber. I have sealed it for now from the outside using bathroom sealant and it is holding but I need to find a more robust solution. Any ideas?

I do have a spare pair of 175 CD-2 carbs I picked up but it is surprising how many small differences there are between these and the jag originals so I am reluctant to use one.

[AussieEtype]

I was getting choke only on 2 carbs and 6 cylinders. No wonder it wouldn't idle properly on choke!

I could be wrong but I thought that is how the choke was supposed to work - only on one bank. The same applies to my V8 Rover with the same carbs - the choke only works on one bank.

Garry

[MarkG]

Gary; When you pull out the choke cable, two things happen; the butterflies open a fraction to allow in extra air through the inlet manifold and into the engine and the choke body moves round to allow extra fuel through pin holes into the chamber. The butterflies on each pair open in parrallel because they are connected to the same spindle and the choke body which is bolted to the first carb has a pipe connecting to the second carb for the extra fueling.

Exactly the same thing happens with the pair on the other bank.

All 4 carbs must work in parrallel. In the case of a twin carb setup like in a Stag or Rover V8 then the pair must work together otherwise you would be applying choke to one side of the engine only and it would run very rough indeed, as mine did

[vee12eman]

Hi Mark,

with reference to the hairline crack, I would have suggested superglue, which being thin would move into the crack by capillary action before setting, then go over the crack with araldite. It is possible to get a 2-part "chemical metal", I think it is made by Plastic Padding, but there are probably others. iused some of this a few years ago when my Triumph Spitfire fuel tank developed a leak. The vent in the cap was not doing it's job and as the car drew fuel, the tank collapsed as it could not draw in air! Anyway, the pick up tube, which is cut off at an angle, a little like a syringe, pierced the wall of the tank. I was working away on a course at the time and the car was full of fuel (Spitfire tank is just behind the seats and all the fuel ended up in the carpet!), so had to ask someone else to go and get some chemical metal for me. He got some from the local Halfords, then I had to remove the tank from the car and apply the chemical metal. All of this took place in the gravelled car drive of a beautiful Stately home in Hampshire, where the course was being held.

Anyway, the chemical metal held, and eventually I replaced the tank with one that wasn't crushed, sorting out the vent in the cap too!

As to throttle bodies, I bought a spare set of carbs from ebay some time ago. Sadly, I threw the bodies away when moving here as space was at a premium, keeping only the linkages and removable parts. Mine came from a Daimler and were cannibalised for spares. Although carbs are nominally the same accross a range of cars, they tended to differ for different engines, as you have found so you'll probably have to find some from a Jaguar/Daimler V12, they were all the same physically, although I don't know whether the needles snd springs differed. I took the opportunity to rebuild them with a kit bought from Andrew Turner, the same as the one available from Burlen Fuel systems.

I suggest keeping an eye out on ebay, or alternatvely try Jaguar Kingdom, 07977995207, possibly they will have some, they were a good source of spares when I was in UK.

Regards

[dhanania]

ok alittle confused. I open the chock all the way up to fire the engine up on cold. I let it run with full chock open for about 5 minutes then drop a notch and set off. Then when the car is warmed up, about 5-8 minutes later, i drop the chock down to the last notch and im fine.

Is this the proper way when a car is starting up on a cold start? or am I doing this wrong?

Please help!