Quoted from crazi:
Checked the coils out of circuit with the diodes off. Slingshots 7 Ohms and Pop 3.7 Ohms (all 3 seem ok to me)
Slingshot and pop bumper coils are the same spec and should measure around 11 ohms. Compare against one of the working pop bumper coils.
Some of the Marco coil wrappers list the DC resistance - see 10.7Ω here: