View Full Version : Merc 165 37L No Spark

05-10-2006, 11:04 AM
"I just rebuilt a 3.7L 165 Merc and I am not getting any spark. To start, the coil is getting around 10 Volts (why not 12?) The battery is new, all the wiring is correctly hooked up. New points, rotor, cap. The plugs my be bad. They have around 12-15K resistance in the wire. Is this normal? I am thinking that there may be a short or it is grounding itself out somehow. Could the timing be 180 out or out just enough that no spark is happening when the rotor makes contact? Please Help"

05-10-2006, 12:00 PM
did you check the condensor or replace the condensor? You might have a ballest resistor in line from the ignition switch. is this the original distributor or a replacement? I would check the points for the proper dwell an and the wireing from the ignition switch to the coil. good luck

Mike Gibson
05-10-2006, 06:58 PM
"You might have the wires backwards at the shift kill switch. If you pull the grey wire at the coil and you get spark, that is the problem. It is also easy to tell because the coil will get hot to the touch with the ignition on. As far as voltage, there is a resistance wire and you will not get a full 12 volts unless the key is turned to the "start" position."

05-10-2006, 07:50 PM
"plug wire resistance sounds a little high. don't have specs here and should not prevent spark. check spark at coil. disconnect tach lead. ground points, should get spark."

05-11-2006, 07:39 AM
Thanks for all of your help. The problem was in the tach (grey wire) on the negative side of the coil. Who would have thought? Thanks again.