BL PRINCESS
HOT STARTING BOTHER
Q
I have a 1978 BL Princess 2 with the 1.7 engine (the O-series unit with a single carburettor and manual choke). The car has been in my family since new and so is a very treasured possession. It is only used on rare occasions, but I have recently had a problem with starting the vehicle when hot. It will always start first time from cold and runs smoothly. At motorway speeds it is trouble-free, however once it gets warm it can misfire and, when coming to a stop, the engine can stutter and die. It will then refuse to start until it has been left to cool down.
I have checked the ignition after a failure and there was a healthy spark. I have also checked for a fuel supply, and upon cranking with the fuel pipe removed there is a plentiful supply of petrol. I am wondering if the problem may be within the carburettor, but I am reluctant to strip it down without further information. James Geeves
AYou have mentioned that you have checked for a spark after the failure of the engine, and I would just confirm that this is immediately after the failure when the engine I still hot? If this is the case, then it would appear that the ignition system is not at fault, but if this is not the case then it is quite feasible that the coil or amplifier could be failing when hot.
If we can completely disregard the ignition system, then fuel vaporisation may be another possibility, as that is quite common these days given the increased volatility of modern fuels compared to the formulations our cars were designed to run on. However, as the symptoms also include a misfire and stuttering when coming to a halt, I think this is less likely in your case as fuel vaporisation would normally occur when the engine was hot and stationary and allowing the heat to permeate up through the carburettor and fuel lines. This situation would lead to the restart problem you are encountering, but it is less likely to cause the misfire on the move and the stuttering as you come to a halt. I wouldn’t totally discount it, though.
However, if you have a good supply of fuel and a good spark, then the problem would appear to be within the carburettor. This being the case, it may be that the needle valve in the carburettor is sticking. With this in mind, it could be worth attempting to free it next time the incident occurs by tapping the body of the carburettor with the handle of a screwdriver. If this does then allow the engine to start, it will be reasonably conclusive evidence that this is indeed the problem. However, if it makes no improvement and there are apparently more serious problems within the carburettor, then there are thankfully still quite a few specialists around who can help in this area – the carburettor on the BL Princess should be an SU HIF6.