1973 Rolls Royce Silver Shadow cold starting problem

If you have cleaned carb filters , does it not also have a fuel filter below the car ? Is the fuel pump clattering away o. k on initial start up . I remember one owner who swore that switching ignition on two / three times before starting cured his cold starting

I have checked the fuel pressure which seems OK; the pump clicks for a few seconds then stops after switching on ignition.

I am now wondering whether it might be an ignition problem despite the engine running well when it gets going.

Could the battery be a little low in charge and the draw from the starter on cranking taking power away from ignition side / affecting cold start ? The theory of switching the ignition on / off 3 times prior to starting was it primed the fuel system better and was sometimes indicative of a suspect fuel pump . One of my friends was the Service Manager of our main RR dealership for more years than I dare remember and would have have been invaluable in giving me an answer to this problem but sadly now passed away . A change of engine oil and filter might help in getting it up to top end and circulating a bit quicker and operating the hydraulic tappets which may aid cold start , but you may have already eliminated or carried this out

Thanks for your further response.

I did try the fuel priming ignition on/off trick but it made no difference. Also, as it happens, the oil and filter were changed very recently in any event and yesterday I put the battery on charge which covered your point. Having gone through all the fuel aspects and most of the electric ones it still leaves me with the problem that is only there when starting from cold.

The only thing regarding the battery is if any weak cells it wont hold the charge which affects the cranking speed and can only be verified by carrying out a load test . With regard to the electrics / ignition , check all earths at battery and wherever the earth/s from engine to body is located . Check engine breather , check all vacuum hoses for cracks / leaks which will draw air . Also noticed you never listed replacing the dist condenser , small , cheap but vital part . Not much more I can do from here , running out of suggestions that may resolve the fault .

Your further response is much appreciated. The battery is only a few months old and in fact replaced under guarantee an earlier replacement which had failed. I assumed that the distributor condenser was replaced by the garage at the same time as the points but it is worth confirming. I noticed that there is a condenser in the ignition coil circuit which looks old and I will test along with the other items you listed. I will check them out over the next few days and let you know how it goes.

I have exactly the same symptoms you describe on my 1975 Shadow. Originally it had single points with no vacuum advance fitted. I have replaced the points with the recommended electronic ignition kit and coil. I believe I have a problem with my fuel pump after having a service kit fitted. However, the car runs beautifully once started and starts on the button from warm or left for 3 to 4 days. This a real brain teazer!!

Thanks for the suggestion.

I have now pinned down the problem to a faulty (but not completely broken) lead from the primary ignition coil to the condenser resulting in a lower voltage than required on the secondary coil. Replacing this lead has solved the problem.

Good news , thank you for updating the forum

So glad you have found a fault and above all shared your journey. I will get my pumps checked by an expert as well as test the coil and lead as you suggest.
Can anyone explain the theory of why this lower voltage problem causes poor starting after 5 or 6 days and not sooner i.e. when warm or cold even after a few days ?

My understanding is that the secondary coil creates a voltage when the current in the primary cuts off - when the ignition points open. For maximum efficiency the primary needs to discharge as quickly as possible to create the highest voltage in the secondary; it does this via the condenser, the other side of which is earthed. The condenser in the first instance charges up rapidly to absorb the discharge from the primary coil; when the condenser charge peaks it discharges to earth. If the condenser or the connection to it is faulty then the secondary coil voltage is too low and fails to produce a decent spark for the plugs, which is particularly critical when starting from cold.