Hi, just to clarify...are we saying that he fuse blows at the first key turned position ? Or when the key is turned further to ignition (before crank position) on, where normally you might get a beep from dash horn ?
If it's on the first turn, you might rule out a load of things. If it is on the ignition position, that is different.
I wouldn't rule out the actual ignition/key switch itself. These can be known to fail easily and result in this very scenario.
My next in line of suspects, would be around that ignition feed to the coil. Or perhaps the relay itself. I have recently known a similar thing to happen on a mercruiser tks engine. The local dealer was working on the engine just before it happened. it was then reported that it kept blowing this fuse and wouldn't start. When I went to look at it (after dealer and owner lost patience), I found that the ignition feed wire had been broken off its terminal and sitting bare and in contact with the top of the engine. It was shorting out as a result. I strongly suspect that it was caused by clumsy footwork from someone clambering or stepping where they shouldn't, was the cause.
Failing anything obvious like that, I would have a look at the corresponding pins, male and female, in the main loom harness plug. check the plug connectors at the injectors too. Think they might be on the same relay.
If it's on the first turn, you might rule out a load of things. If it is on the ignition position, that is different.
I wouldn't rule out the actual ignition/key switch itself. These can be known to fail easily and result in this very scenario.
My next in line of suspects, would be around that ignition feed to the coil. Or perhaps the relay itself. I have recently known a similar thing to happen on a mercruiser tks engine. The local dealer was working on the engine just before it happened. it was then reported that it kept blowing this fuse and wouldn't start. When I went to look at it (after dealer and owner lost patience), I found that the ignition feed wire had been broken off its terminal and sitting bare and in contact with the top of the engine. It was shorting out as a result. I strongly suspect that it was caused by clumsy footwork from someone clambering or stepping where they shouldn't, was the cause.
Failing anything obvious like that, I would have a look at the corresponding pins, male and female, in the main loom harness plug. check the plug connectors at the injectors too. Think they might be on the same relay.
