I have a 99 ram 1500 van with 5.9 I've never had any issues with it & always starts almost immediately when I hit the key until a couple days ago, I got in it after it sat for about4 hrs since I drive it last & I wouldn't start period but cranked on & on no problem, I narrowed it down to a spar issue, no spark to the plugs but I got spark out of the coil wire going to dist. I check using a screwdriver & ground so I figured it had to have a failed cap or rotor so I inspected them & they looked fine but I've seen fine looking ones fail, so put new ones on & same thing so now I double check my spark again using 3 different types of spark checkers one with an online light & two others that shows sparks, the only one that showed spark was the in line one with a light, but the light was dim but it was there, the other ones showed nothing & a note the spark I saw was yellow & not blue so I'm assuming I have a weak spark & it doesn't have enough voltage to complete the circuit all the way to the plugs & why the dim light or no spark on other testers. Now in my experience modules or ignitors won't create a weak spark, they either work or they don't, but a coil can produce a weak spark causing hard starting etc... So I believe I have a bad coil. I'm working on the van right now so any input on my diagnosis would be appreciated & van will not start.

 

How is battery voltage?

 

Parts stores like Autozone can bench test the coil. I've only replaced two failed ones in my life and one of those was rodent damage. They just rarely fail. If your battery is fully charged, get a digital volt/ohm meter. Set it to ohm and test your plug wires. Put the electrodes in each end of the wire and move the ends together. If the ohm reading changes a lot, you may have plug wires.