My 88 Cherokee won't start after sitting for several months. Checked fuel at the filter and it looks clean without water contamination. Pulled a plug and checked spark with engine cranking. Spark looks yellow, not blue as I thought it should. Is that a weak spark? I've changed the coil recently, is it ignition module, or something else? When I first tried to start after several months, it started briefly, then quit and won't restart. Battery is strong, engine cranks good.
