Stripped, cleaned and rebuilt the carbs - with a kit from moss motors.

car will start then dies

Car will run if pressure on the gas pedal is applied, will rev etc. soon as you take foot off the gas - dies.

idle screws have zero impact on the situation, backed them all the way out. In ½ turn intervals and tested.

carbs leak like a sieve and so does the aux carb

new floats and needle valves

checked and adjusted the float heights, even made the height lower to force earlier cut off.

am completely stumped.

going to pull the carbs today, and check specifically the idle circuits, with pipe cleaners and compressed air incase it’s got crap in it

any tips?

 

You shouldn't be backing the idle screws all the way, you need to "seat" them all the way in LIGHTY SEATED. (clock wise)
Then screw them out 3 turns as the first setting.

As for gas all over the place.

You have the dash-pots off -
Carefully remove the pistons so you can see the main jet on each carb.
Turn the key on and allow the fuel pump to fill up the float bowls _ the fuel should stop just short of the main jet at about 1/16 below its shoulder.
If it over flows, even a little, then you still have a problem with your floats and/or the needle valves leaking and/or incorrectly set.

They could be defective out of the box, but unlikely, but you never know.

Also, when adjusting the fork that comes in contact with the floats, don't put pressure on the needle valves.

Are the needle valve housings seated properly, there should be a small paper gasket in there _ I like to use some Hylomer here _ some grease on the male and female threads too.

 

Point I was trying to get over was…. Doesn’t matter where the idle screw is set, zero idle, no difference… stated at base settings (manual says 2.5 turns) and tried to start. Back off 1/2 turn, try, 1/2 turns, try etc… will start as soon as I touch the gas pedal, but back off the gas pedal and it does regardless of how far I. Our out the idle screw is.


pulled the carbs, floats set, blow test = can cut off flow by lifting the forks..

when assembled, it gushes up like a drinking fountain out the jets, I suspect at this stage my fuel pressure is way too high?

why else would it bypass the idle circuit??

no other idea what could be wrong, but have bought 2 cans of carb cleaner and I’ll be going to town this week.

 

Fuel pressure too high; what are you using for a fuel pump is the obvious question ?
These Chinese electronic fuel pumps never work well with SU carburetors.
It's not so much about fuel pressure, but volume, that applies for any carburetor, all the pump has to do is keep the float bowl filled.

If you want to introduce pressure into things, then it should be no more then around 4 Lbs.

Until you fix the fuel gushing out the jets like a fountain, obviously the car won't run very well (I'm surprised it runs at all)

Also sounds like the linkage is not adjusted properly to let both butterfly valves to shut right tight.
No air should flow through their at idle.

It runs because as soon as you touch the gas pedal, you're letting air into the engine, other wise with all the fuel, it's just flooding.
Carb cleaner isn't going to do anything until you solve the fuel delivery problem.

Once that's dealt with as I described in my first post about where the fuel level should be, then we can move onto the idle circuit.

EDIT:
After looking at your photos: it looks like you're using the hard bake-lite heat sinks on both carbs, they need a green (usually green) gasket on both sides to seal properly.
The way they sit now, it's not sealing there well _ vacuum leak, that is one reason why the idle screws can't be set. (RED ARROWS point out where the gaskets should be)

The vacuum port arrowed out in green has to be blocked off, otherwise there is a vacuum leak there.(you may temporarily block it off with something)
If you attach it the the vacuum advance on the distributor, then that will be OK, assuming that the diaphragm holds vacuum.

Check it with a small hand held vacuum pump, if you don't have one of those, take a long vacuum line and use your mouth, most people can create enough suction to see if the diaphragm has failed or not.
And the thermostatic solenoid has to be in place, otherwise there is going to be MAJOUR vacuum leak there !

 

Fuel pump is the square body OE type. Had one in a box within the many spares that came with it. Brand new old stock with a warranty cert from 1965.

floats float, valves valve, set to the height using a brass dowel of the correct thickness, 2 others suggested adjusting a bigger gap to make the floats cut off gas sooner… still gushing…

 

Now I’ve seen the edit with photos… yes the vacuum is blocked (just not in the photos) - 3” of hose with a screw in it to seal.

the mounts have 2 gaskets per carb, one each side of the plastic spacer (red - came in the SU kit)

 

It also looks like the choke is missing some bits, the screws should be in place ((green arrow)
The cover is missing (red arrow)
Most importantly, the small locking tab looks to be missing, this stops the adjusting nut for the choke (pink arrow) from rattling around and keeps it set. (the locking tab doesn't seem to be shown in the picture)

You screw the nut in to lean the choke out and screw it out to make it rich.

 

If I think of something as to why the fuel is puking out the carbs, I will post again.
I've gone over what the problems could cause that.

There are only so many things that can cause that, and I've covered all that I can think of.
You have the correct pump, you've adjusted the float needle valves properly or at least what you have described sounds correct _ something has not been done correctly though.
You didn't comment on my question though, did you put the small paper gasket under the needle valve housing into the float lid ? Did you use some Hylomar here ?
Although that would be a very small leak and it would be unlikely to cause that much fuel to bubble out the jets.
Do the floats them selves have fuel in them, they shouldn't ?
Do they slide up and down feely on their shafts, in the past I've had to polish the shafts with some steel wool so they don't bind. (I use course steel wool rather then any type of paper because I can take a magnet to get any steel wool fibres out of there, the grit from any type of sand paper is not so easily removed) You don't want that grit getting into the engine, but a steel wool fibre will just blow through.
Others will post...

 

All the aux carb parts are present, just removed to troubleshoot as gas bubbles out past the needle in the center of the aux carb..

no to the paper gaskets, wasn’t present in the carbs on disassembly, wasn’t present in the refurb kits. There were red fiber washers in the kit and I used them.

was tempted to plug the aux carb as here in Arizona I doubt I’ll need it.

also tested the solenoid with 12v and it does actuate… hard to tell if it works in place as it’s 106° in my garage.

 

I will chime in with my ten peneth worth although everything has already been said really.

The fuel is only pressurised by the pump to get the fuel up from the tank to the float chamber. The engine does not use pressurised fuel only vacuum fed fuel. Once the fuel has been pumped to the float chamber and the float closes the float valve the fuel pump recognises, via back pressure that no more fuel is required and shuts off. (When you switch the ignition on the pump ticks and eventually stops when the float chambers are full.) If the pump does not stop pumping fuel and the float chambers are leaking then the fuel is still being pumped into the float chamber which indicates a fault with your float or float valve. The floats have been known to spring a hole and fill up with fuel causing them to sink which means the float valve is not being closed. If the float height is not set correctly then the float valve is not being closed and fuel will continue to enter the float chamber and find any hole to leak from as it is at this point under pressure from the fuel pump and the fuel level is pointless. Setting the float level lower so there is less fuel in the float chamber is better than having it full to the brim.
With the tops off the carbs turn on the ignition, listen to the fuel pump tick and watch the needle valve seat. If the fuel starts to flow up through the needle valve seat then your float chamber levels are still too high. If the fuel is leaking here then the float valve will not close and the fuel pump will just keep pumping until the tank is empty and you have fuel all over the garage floor.
This part is important as more engine fires are caused by over flowing fuel from badly set floats than electrical fires. (in my opinion.)

Below is a diagram of the carbs and the fuel levels. The line 21 is the fuel level when the float valve is closed.


If the fuel level in the float chamber is too high then fuel will leak out of the needle valve seat in the mouth of the carb and the AED will overflow if the fuel pump is still pressurising the float chamber..

Setting the slow running should be done when the engine is hot regardless of the ambient temp in your garage. Before setting the slow running screw to its starting position you have to balance the carbs. The butterflies on both carbs have to be closed with the slow running screw screwed fully screwed out so not effecting the butterflies. To do this there are bridging clamps on the spindle between the carbs. Loosen off the slow running screws, then let off one of the bridging clamps. Remove the top of the carbs so you can get a finger into the mouth and physically push both butterflies shut. They should be shut at this point anyway as the carb springs should be pulling them shut. I like to twist the spindle and let the butterflies snap shut on the springs. Once both are seated correctly then tighten up the spindle clamp and then you can screw the slow running screw down to its start position which is either 2 1/2 or three turns.

 

Thank you @Cass3958

makes sense, so seems issue is with the float chamber area on both carbs.

ill try the wire wool on the central shafts in the chambers incase that’s making the floats bind. Floats float. Tested in a jug of gas. They are brand new from moss.

I did all the steps re butterfly valves etc, issue is, if I can’t idle I cant make the engine hot for all these adjustments, its so frustrating.

peter

 

Welcome to the joy of owning a classic Jaguar.
Shame part is that there are not many of us old folks around to give this advice for much longer. Younger people are not interested in cars from the 60s. The younger generation who are just coming into money to allow them to own an older car are going for the cars of their generation which is why fast fords from the 1990s are costing so much to buy today where as the price of our Jaguars seems to be falling.

 

Same with triumph cars (have a 1980 spitfire)

as for my issue, have gone to town on the float chamber spindles and tossed the floats back in and it feels like a much happier union!

I’ll keep cleaning and reassessing

 

Another thing, your brass round stock that you used to set the float levels, it is 7/16 right, not 3/8 ?

 

absolutely - amazons finest

 

Have you adjusted the tab on the back of the float fork so that it doesn't fall too far into the float bowl ? (red arrow)

Another thing that I've had happen is the area (green arrow) where the needle valve comes in contact with the float fork has worn into a concave dip.
This causes the needle valve to bind there, even more so if the adjustment tab on the fork is not correct.

To correct this, I took a small flat punch to push the worn spot out, then filed and polished it flat.

I wonder too if you have the correct needle valves in your kit, a shorter needle valve housing would certainly cause your "fuel fountain" issue.

I'll check the length in the morning and post that, it's almost 1:00 A.M. now.

 

I’ll send photos later - both forks are brand new needle housing the same same size as the original from ‘62

 

Try this, go to your hardware store or where ever and get yourself a 1/2 bolt with a long shank that can be used to adjust the float fork.
You do not want to use the threaded part; an inexpensive Chinese bolt will work well enough.
Cut off the excess and the head with a hack saw.

Bend it where the Blue arrow is.
If your needle valve is spring loaded, then the fork needs to be adjusted on the "uncompressed" height.

 

[img alt="Original on top
New on bottom"]https://cimg0.ibsrv.net/gimg/www.jaguarforums.com-vbulletin/2000x1504/img_3396_5230d4e4ae2d352b22f7b4a2914ee852de41e922. jpeg[/img]
Original on top New on bottom

Used the 7/16 rod to adjust, but under advise from Jagvet and others made the bend larger for a quicker cut off.


I have cleaned the spindle that guides the float with wet and dry paper, I did notice that the float moves freer up and down, no snagging.

 

The top tip looks OK, but the bottom one looks damaged with a groove in it, or some material missing.
I would have ordered the parts from Burlen Carburetors.

The new bottom one does look damaged.