I've never seen this before so I wanted to see if any one has had this issue. I have a 1969 Ford 3000 gas tractor that I got as a project. The tractor has been running for about a year when it started to get progressively harder to start. I pulled the plugs to check for spark and I noticed that while cranking the plugs do not spark. But once I let off the key from cranking the plugs will fire. This explains why the tractor only starts once I've let off the key. To be clear, if I hold the key and crank away the engine will not fire off until I have released the key. Has anyone else seen this before? I am really at a loss to why this is happening. Any help is appreciated.