Poor starting

[rsawatson]

I have recently rebuilt my carburettor (new jet, jet bearing, needle valve and needle) and reckon I have tuned it about correctly. I have been on a drive today and the plug colour is a light grey and the electrode is clean.

However, I am experiencing problems with starting. From cold, the car is an absolute pain to start - I have tried various choke settings, and the only way I seem to have been able to get it to start is to give it full throttle until it just 'catches'. The battery is in good condition, (although I have been wondering about whether the starter motor itself may be perhaps causing problems), and once running it seems to tick over nicely. When warm, the car is not particularly eager to start either (it's easier, but throttle is required). The idling speed is set to normal. The electrodes on the cap look a little blemished, so I shall replace that this week to see if that eliminates anything, but I have seen much worse. I have checked the points gap and that seems to be fine and the points are in good condition. I have not checked the timing, although this has been checked within the last year and I have not moved the distributor since.

The car was starting fine a few weeks ago (albeit prior to setting up the carburettor properly; it was running far too rich and the plugs sooted up to such an extent that I stuck a new set in). After replacing the plugs (and not touching the carb), the car started fine. I then adjusted the mixture to make it less rich, and I am where I am now.

My immediate assumption is that it's probably carburettor related, as this is what I have adjusted recently. However, I don't understand why (if this were the case) that it is still reluctant to start with the choke pulled out. I often find that problems tend to coincide in an annoyingly deceptive manner, so was wondering whether anyone thought what I'm experiencing is more indicative of an electrical fault - perhaps a weak spark - before I go through the rigmarole of testing/changing things and potentially chasing my own tail!

Thanks in advance.

[oliver90owner]

While it would appear that the mixture is the likely problem, the spark quality can be checked by removing the plug leads and checking spark colour and strength by cranking with the starter motor and holding each connector close to a metal part of the engine. Timing is important and valve clearances must not be tight. A general service tune up might be in order, before proceeding further?

If it won't start on continuous cranking, check the plugs for wetness. It may be too rich, if the throttle needs to be wide open.

RAB

[myoldjalopy]

Maybe you over-adjusted the mixture? Assuming you rebuilt the carb correctly, and then after it ran well, you adjusted the carb setting to compensate for an over-rich mixture, after which it became hard to start - maybe its now running too lean? Enrich the mixture a bit, after you get it running again, and see if the car performs better. Is the choke cable connected up correctly so that it is operating properly?

[firehor5e]

new manifold/carb gaskets fitted corectly?ie letting in air causing a weak mixture.did you top up the carb damper oil?

[rsawatson]

Thanks all for your advice.

I did some experimenting after work today - I began by investigating the carb (tightening up all nuts on gaskets, ensuring that the inlet manifold was secure etc, experimenting with various positions on the mixture adjustment) and found that the setting I'd got it at was the best. As said, it was the starting up which was causing me the most problems - running was fine, although still a bit rough.

Having exhausted avenues there, I then moved over to the ignition side, where I think I've found a fault in the low tension circuit. I swapped the coil with a spare and noticed that the situation improved immediately, but when swapped back to the original coil it was just as good. I then let it cool and started it again - likewise, no problems. The low tension wire from the coil to the distributor looks as though it's seen better days (or the connection on the spade at least) and I reckon that moving it around has improved a temperamental connection. This is just a theory at the moment... but so far it seems to be proving correct!

Thank you again for your help. Hopefully that'll be the end of it!