Sometimes i can't get the engine to turn over,

Does the oil and battery lights go out or dim when you turn the key to start. If they do then you have a bad connection on the main cable going to the starter if they don't then it's most likely its the small wire on the started that's the problem. To check the small wire on the starter put the pickup in neutral take a piece of wire from the small connection on the starter and touch it to the positive of the battery the starter should turn over. If it wont turn over then the problem is in the starter if it turns over then the problem is a short circut in the wire from the key switch to the starter. The short circut could be a blown fuse or the key switch. It may be the wire itself but this is very unlikely. Cheer's