16-08-2018, 12:46 PM
Modern fuel certainly seems to be causing problems in the wider classic car world, especially with rubber components in the fuel system - as others have said, flexible fuel lines, pump diaphragms and filler seals all seem to be affected. I have encountered collapsing hoses and disintegrating pump components, and know several other owners who have experienced similar problems. I am not a chemist, so have no way of knowing whether ethanol is the problem, or some other constituent of modern petrol.
Another problem I have encountered is stale fuel in a car which had been unused for eighteen months: the engine started and idled with no problem, but under load it misfired and progressively lost power. The solution proved to be a set of new plugs; apparently under rich mixture starting conditions the stale fuel leaves a varnish on the plugs which breaks down the insulation and cannot be removed.
Another problem I have encountered is stale fuel in a car which had been unused for eighteen months: the engine started and idled with no problem, but under load it misfired and progressively lost power. The solution proved to be a set of new plugs; apparently under rich mixture starting conditions the stale fuel leaves a varnish on the plugs which breaks down the insulation and cannot be removed.