Chan HT

Car, a 1998 WRX with Possum Link ECU has been experiencing starting problem, ie unable to start usually in the morning. This morning, after 6-7 long start attempts, the engine just refuse to fire up. Fuel pump priming ok which I always wiat for the fuel prime to complete before turning ignition switch to START. After 2-3 hours, I came back and try to start her up and the minute I turn the ignition switch to ON, there was some sort of detonation in the engine which I can feel the engine turn a bit through vibration and some faint pop sound from the exhaust. This is obvious as excess fuel in all the cylinders from previous 6-7 start attempts. After fuel priming completed, I turned the switch to START and she fired up with ease.

What puzzled me is why there is detonation in the engine when ignition switch was in the ON position. The spark plug or plugs must be firing to burn the excess fuel. Spark plugs are two months old. This problem of unable to start usually occurs in the morning but it has occur twice when engine was fully warmed up. Problem occurs about 4 months ago. Ignition coil was replaced about 5 years ago. BTW, once she fires up, all normal. Generally I believe most ECU (if not all) do not fire up the ignition when ignition switch is in the ON position.

Any advice ? Thanks.