I’m a long-time listener to the show but a first-time poster here. I’ve got a 1998 Jeep Cherokee Sport 4x4, 4.0 L I6, automatic, 169k miles, that often cranks but doesn’t start up. When I cut the power and try again, it starts up right away. I’m concerned this workaround will one day not work and I’ll be left stranded, so I’d like to fix this if it’s cheap and easy. The symptoms suggest either a lack of fuel or lack of spark due to an electrical problem, so I replaced the ASD (auto shutdown) and Fuel Pump relays, but they made no difference. The other two relays - Starter and Cooling Fan - seemed irrelevant. Anyone have any other ideas what this could be? Maybe the crank angle sensor? (I’m not even sure where that’s located.)
Next time just turn the key to the run position rather than all the way to start. (i.e. just until all of the dash lights come on). Then back off…then back to run…back off…run… and do that about 6-7 times and then crank it. If that works then its probably a check valve problem at the fuel pump. This keeps the fuel in the fuel lines from running back into the tank when the car is off. The fuel pump energizes for a couple of seconds every time you turn it to run - thus the key on-off action is pumping fuel back up into the lines. If this is it then the fix is to replace the fuel pump.
Cigroller is correct and yes, the cure is to replace the pump as the check valve is in the outlet tube of the pump. It’s a BB sized ball held onto a seat by a small spring and over time the ball and seat may wear a little which then lets pressurized gasoline bleed back off into the tank.