Cold start carb

[colinM]

The Mk2 wouldn't start yesterday, seems to be the cold start carb playing up. Got her going eventually but what can I do to check the operation of this?

[Martec]

I assume I'm teaching my granny to suck eggs but, if you have the original system then a temperarure switch located in the front end of the inlet manifold senses the jacket water temperature and puts power onto the solenoid to lift the piston on the 'starting carb' (between the two HD6 main carbs).

The switch (I'm sure someone will give it its correct name, otter?) is well known to be a bit problematic and is often bypassed to switch it on and off from the cab.

If you bypass the switch with a bit of wire, then the carb should operate (hissing away like mad with the engine running).

If it still does not operate then check the wires to the 'Starting (Auxiliary) carb', there is a delicate 'plastic' black cover and as you carefully lift this the two wires are only sat on two pins, it is worth cleaning the pins and wire loops that sit on them. You can also check the solenoid coil with a multimeter. I think it is unlikely the solenoid plunger and flat topped valve will be stuck, but worth checking the movement and the spring.

This 'starting carb' throws petrol in with a bucket, so I have wired it from the cabin and switch it off when the temperature gauge gets to 50.

I have fitted a new needle to this carb but it is still difficult to get it working across the the temperature range, so use the throttle to help keep the engine running for the first 5 minutes.

Best wishes

Brian

[PPV]

Martec is right with it being called an 'Otter' switch which is its name. I took mine apart when playing up and cleaned the contacts inside and then it worked. However, I decided to repace it with a new one from SNG and keep the old one as a spare! Don't know where it is now though!
The service manual on pages C19 to C21 give a good description as to how to adjust and a picture of the 'otter' thermostatic switch.
Regards,
Paul

[colinM]

Thanks for the advice, when trying to track down the problem I shorted the lead from the switch to earth and could hear the solenoid clicking, so tried again and the engine started. It seems to be working OK now so it may just have been a loose/dirty spade connector on the switch. At least I know what to look out for if it happens again.

[oldtimer]

Well, Colin M, it will happen again !

Martec has got it right again, Bless him, so have another read.

What can I add ? Not a lot. Perhaps the following:-
When you switch the ignition on listen for the fuel pump.
When you have started the engine don't leave it running cos it will choke it's self to death - then you'll have a problem.

From memory that choke arrangement was incorporated in my 1937 saloon, mk5 , 7 ,9 ,3.4 &3.8 mk2's also the old S type. So well tried and tested, you could always guarantee a start even in sub zero temperatures.

And finally try buying a book and study the finer points of how it works

Oldtimer

PS If you haven't got a switch in the cabin to bypass the Otter switch - fit one tomorrow.

It's also an Otter switch used in radiators to turn on Electric Fans