650 Merc no fire to coil

[mwbaughan]

New switch box - have power to red on box. No fire from green to coil. I put a new coild and switch box on. What next?

 

[achris]

Re: 650 Merc no fire to coil

Trigger. Is it a distributor engine?

 

[mwbaughan]

Re: 650 Merc no fire to coil

it is a type 3 cd pointless distributor according to my manual

 

[achris]

Re: 650 Merc no fire to coil

Check that you have 12v on the white wire on the switchbox (the one next to the red wire) when the key is "ON".

 

[mwbaughan]

Re: 650 Merc no fire to coil

1975 3 cylinder, checked and I had fire from the stator at the rectifier also<br /><br />just no fire out of the green to coil - even with a brand new switch box<br /><br />isn't the brown harness wire supposed to go to the brown on the switch box?<br /><br />someone had my brown harness wire running back to a yellow on the rectifier(from stator) my old<br />mechanic no doubt - that never got it going needless to say.

 

[mwbaughan]

Re: 650 Merc no fire to coil

my test light lit up on the white but I remember that it was kinda faint compared to the red

 

[achris]

Re: 650 Merc no fire to coil

Should be exactly the same as the red. Use a multimeter, not a test light. If the white is down on voltage then start looking around the key area for bad connections. If they all check out, then jump the red wire to the white (at the switchbox) and see if you get spark. If you do, then think about changing the key switch.<br /><br />The brown wire going to the yellow on the rectifier is correct.<br /><br />Chris..........

 

[achris]

Re: 650 Merc no fire to coil

one more thing worth checking it to disconnect the mercury tilt switch. that's the brown wire that goes to the other brown wire on the 3 terminal side of the switchbox.

 

[mwbaughan]

Re: 650 Merc no fire to coil

just checked 12 volts to both whites and red on box

 

[achris]

Re: 650 Merc no fire to coil

This is a post from someone with the same problem as you. The engine sizes are different but don't worry about that, the troubleshooting is the same.<br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=29;t=013507 <br /><br />Look at the post by Chris1956, it gives a good procedure for checking the trigger (inside the dissy).<br /><br />Chris.........

 

[mwbaughan]

Re: 650 Merc no fire to coil

i unhooked the mercury switch earlier - figured that would rule that out <br /><br />so the harness brown just goes to the yellow on the rectifier and not the box at all? looked like it used to go to the box - then someone jumped it from near the switch back to the rectifier.<br /><br />oh by the way this switchbox only has one terminal side - not like the diagram

 

[achris]

Re: 650 Merc no fire to coil

OK, I've got the diagram for your engine in front of me. That brown wire is the pulse wire for the tacho and should be connected to the yellow on the rectifier. Yes, it used to be on the switchbox but the tachos want a 12 pole pulse and from the stator is more reliable. <br /><br />Trigger test procedure.... <br /><br />DISCONNECT BATTERY<br /><br />1. Turn off ignion<br />2. At the switchbox disconnect all 3 wires from the distributor.<br />3. Remove the HV lead from the coil to the center cap (remember it unscrews from cap)<br />4. Reconnect that HV center lead to the COIL side only.<br />5. Position that HV lead about about 3/8" from ground (block, shrouds etc) and find a way to hold it there.<br />6. Jumper the blue and white/black terminals on the switchbox together.<br /><br />RECONNECT BATTERRY<br /><br />7. Check that you have +12 V at red terminal.<br />8. Turn on ignition and verify +12V at white terminal<br />9. Touch the black terminal to ground - unit should cause spark each time you touch ground.<br /><br />If that passes and it won't fire at all, suspect the trigger.

 

[mwbaughan]

Re: 650 Merc no fire to coil

i will try that test but mine is not the same sw-box<br /><br />brown terminal is just above the green - is a wire supposed to be hook to the brown on the switch box? if so from where?

 

[mwbaughan]

Re: 650 Merc no fire to coil

oh I see now - got post on change for tach<br /><br />will go check triger now

 

[achris]

Re: 650 Merc no fire to coil

No wire on the brown terminal. I have copied and modified the test to suit your engine.<br /><br />Chris.........

 

[mwbaughan]

Re: 650 Merc no fire to coil

I got spark to ground with the test so it must be the trigger. What's next?<br /><br />thanks....mark

 

[achris]

Re: 650 Merc no fire to coil

Replace the trigger!

 

[achris]

Re: 650 Merc no fire to coil

One other thing. Take the dissy cap off and check that the rotor is turning. Hate to replace the trigger and find the drive belt or dissy shaft is broken.

 

[mwbaughan]

Re: 650 Merc no fire to coil

how do I get to it - I need the merc for dummies version!

 

[mwbaughan]

Re: 650 Merc no fire to coil

oh no - do I have to get a whole new dist housing?