Mercury Sport Jet 175 Cranking but not starting after leaving battery on over night

[Marinaman]

Hi Guys,

My engine is turning over but won't start after leaving the key in the ignition with the power on over night. And yes I recharged the battery but it still won't start. I changed the spark plugs and cables with no joy. It was starting fine before this as it had just had a good going over by a mechanic. I even tried putting a little fuel in the cylinders which didn't work either..

I thought I would ask on here to see if it might be a simple fix before sending it off to the mechanic again..

Thanks!

 

[Texasmark]

You didn't accidentally hit your "kill switch" did you? Makes no sense that what you did would cause you any harm. Only thing I see would be the battery which you said you recharged. First thing to expect would be an electrical problem. Is the starter rolling the engine at a normal speed for that engine?

If so, move on to ignition. Get a timing light (easiest) and check for spark at the spark plug wires. If no timing light pull a plug, with the wire attached, ground the case of the plug to the engine block somehow, not to paint, to bare metal, and see if you have a spark. Got spark, chase fuel related issues.

No spark: You didn't say what year engine you had so this will just be a general answer that someone more familiar with your engine can answer. Check for power to your ignition system and ensure that the engine kill wire at the ignition source (CDI modules on my engine, switch box on others), coming from the control box ignition key, (in the OFF position) is not grounded.