No Spark- 1973 Merc 650 3cyl

[joblo33]

I bought this cheap motor with no spark and have been trying to determine the cause for a couple days. When I bought it there was cracked coil, so I replaced the coil with one from another 65 in my yard. I've checked all the wiring and rewired it entirely twice now. Is there a way to test the black box for this motor? Is there a way to test the distributor? What should I be getting for an ohm reading on the coil?<br />Thanks,<br />Eric

 

[Laddies]

Re: No Spark- 1973 Merc 650 3cyl

Eric you can test that trigger just like the 4 or 6 cyl battery CD

 

[joblo33]

Re: No Spark- 1973 Merc 650 3cyl

I'll test that.<br />Thanks,<br />Eric

 

[joblo33]

Re: No Spark- 1973 Merc 650 3cyl

Ok, no spark from the HV wire when I bypass the trigger. How do I test this coil? Powerpack?<br />Eric

 

[phatmanmike]

Re: No Spark- 1973 Merc 650 3cyl

on the side of the powerpack/switchbox...<br />red terminal should have constant 12v<br />white terminal should have 12v when key/ign swicth is turned " on "<br /><br />disconnect and throw away the blue mercury switch on the other side of the switch box, the side that feeds the distributor. its probably grounded out. throw it away.<br /><br />try these and report back

 

[joblo33]

Re: No Spark- 1973 Merc 650 3cyl

Yes, red has 12v and so does white on key on. I already tested the Mercury switch, there's no continuity to ground through it so it's good. Tomorrow I'm going to go borrow a coil, distributor, and powerpack and replace them one by one to see what fixes it. I'm just trying to narrow it down to one of those tonight.<br />Thanks,<br />Eric

 

[Laddies]

Re: No Spark- 1973 Merc 650 3cyl

Eric, I assumed that you had probable read the test for the system, sorry not to have went through it on my first post, spark gaper in the coil or engine one #1 and plug in the wire, plug grounded, all three trigger wire disconnected from thr box, a jumper wire installed between the white,blk and the blk terminals of the box, turn the key on and arc the blue terminal to ground if you have spark, you have a bad trigger and if you don't the switch box is bad

 

[joblo33]

Re: No Spark- 1973 Merc 650 3cyl

Ok, I'm pretty sure the triggers bad, I'm going to borrow one tomorrow and try it if I can get to the mechanic's house through the snow to get it .<br />Eric