The 'E' Type Forum

Hello,
My friend has a strange problem which someone might know the answer to
He has a S2 Roadster, 4.2 with electronic ignition fitted. The carbs have recently been rebuilt (by Southern Carbs)

The car starts fine, and runs fine, although when pulling up to a junction or roundabout it cuts out. It starts fine again when you turn the key after it has cut out.

We were thinking maybe fuel pump? It has also been suggested the crank is floating - it does seem to be related to pressing the clutch when idling

Thanks for your help

Certainly not fuel pump : it takes about 30 seconds or even more to lower the fuel level in the float chambers to a point where the engine will cut , and you would certainly experience fuel starvation symptoms in normal running. It is commonly a result of 1. too low an idle setting on the 3 large bleed screws 2. wrong level in the float chambers - too high and you get surging when braking to a halt which causes rich mixture cut , or alternatively too low a fuel level which causes fuel starvation under braking 3. too weak an idle mixture setting . The simplest and most common is no.1

Without wishing to teach my grandmother etc. it is often not realised that with HD carbs which are properly setup the butterflies are completely shut at idle , with the mixture bleed occurring exclusively through the passages governed by the large screw on each carb

Out of interest Chris...

If the float level is believed to be set correctly and the ignition is turned on (until the pump stops) - visibly - how far down the jet is the actual fuel level?

Obviously you have to remove the damper and needle to see it but is it flush with top of the jet or 2-3-4-5 mm down?

Im not convinced i have the float levels right.

Well, it depends amongst other things on how far the jet is down . However, if it is level with the top of the jet when seen without a needle, then I would say it is definitely too high . In general terms, I usually set the jets initially down by about 65 thou ( about 1.65 mm) from the top of the jet holder , and at that level you can see fuel in the jet but it is well below the level of the top of the jet so that there is no danger of flooding when the needle is present . I am sorry I cannot be more precise than that , and I must confess that I have found setting float levels a very hit and miss affair , so that I certainly would not pretend that mine are accurately set - what I try and do is set all 3 so that if one takes the lid off the float chamber , the float is about 2/3 of the way up the chamber and the level in the jet is visible but not near the top

Going back to the original post , I should say in relation to the possibility of crank thrust wear that

1. It is not very common on XK engines, compared with e.g the TR6 /Triumph 2.5PI motor where the thrusts frequently fell out

2. The first test I would do is, with the engine at a stable idle , depress the clutch pedal - any appreciable slowing would be a warning sign warranting further investigation

3. With the engine stopped, use a lever and a block of wood on the front frame to force the crank pulley backwards as far as it will go. Get an assistant then to depress the pedal fully and observe the crank pulley - usually if there is anything to worry about the movement forwards will be gross and obvious as the nominal permissible end float is only 4 to 6 thou
( 0.1 to 0.15 mm)

Thanks very much for the advice, I'll let you know what happens

Here is what was wrong (and apologies, this explanation is 3rd hand)
There was a wire hanging down out of place, that was being nipped by the clutch that was cutting the engine out. Somehow it was worse when hot - not sure how though.

Thanks for your suggestions