with no spark. Could anyone advise me on troubleshooting the ignition system and also what year is it please? Have looked on the guides but the only match seems to be a 4A?
Thanks for that diagram achris, it's allowed me to eliminate the kill switch as the problem. Do you know any diagnostics i can perform using a digital multimeter to narrow the problem down further?
I assume you don’t have a DVA for your multimeter…
Disconnect each of these wires from the switchbox before metering. Start by checking the charge coil (brown wire). Meter to ground, you should see some resistance, but not a short. Do the same with the low speed trigger (white/green), and the ignition coil (brown/white).
With the system wired up, check for about 200-400 volts on the charge coil as you pull the starter, and about 2-4 volts on the trigger. If either of those is missing, then disconnect the wire from the switchbox and check again… If the volts appear when disconnected, then you may have a short in the box. If everything is ok going into the box, then measure the output, should be about 400 volts. If there’s still no spark, then the ignition coil is faulty. If the voltage isn’t there, disconnect the coil and measure the output again. If the voltage is now there, then most likely it’s the coil; although it could still be the switchbox…
The only other thing to check is that all the grounds are clean and tight..
Good luck… HTH.
Chris……….
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The world takes on a whole new perspective when viewed from 100' below...
1972 Bertram 'Bahia Mar' 20
2006 Mercruiser 4.3MPI (OW617679) w/Alpha 1 Gen II (OW829301)
I checked the resistances and they all looked good. I have no DVA so my friend and I tried his Fluke multimeter with a little success. Then I had my first brainwave and got out my trusty hand-held oscilloscope and started measuring. I got a voltage from the low speed trigger (green / white), a good voltage from the Brown and the same from the coil feed but still no spark. I was just about to give up and blame the coil when the second brainwave came over me. I swapped the low and high speed trigger wires around and hey presto a fat blue spark! Diagnosis - Low speed trigger not performing correctly. A bit more scoping shows a weak and variable waveform for the low speed trigger and a well defined, regular high speed trigger waveform.
After all that , do you know if there is any adjustment that can be performed on the low speed trigger coil or do you think it may be dead?
It's so simple you'll kick yourself for not coming up with it yourself..
What we are trying to do it to read the peak voltage of a quick pulse.. So, we set the meter to DC volts... We try to load the circuit as little as possible, of course... We pass the signal through a diode (to rectify it, half wave is enough, use a 1000volt diode, 1N4007) charge a capacitor up to store the charge for long enough to see it on the meter. So the cap would go across the meter inputs. We also need a resistor to discharge the cap. I did the calculations for cap and resistor size a long time ago... and I'm in bed at the moment, so I don't have them to hand (even if i did remember where they are)...
From memory....
I based it on a time constant of about 1/3 of a second... RC=1.1T.. I think I used a Poly cap, high voltage of course. I think about 1uF for the cap and resistor about 300K. With this setup you get the best results with an analog meter... I haven't designed one for a digital meter, yet
Have go at that... Let me know what you get....
Chris.......
The first computer I programed was in machine code (hexadecimal)! The computer had core memory... Pre-dated RAM by about 10 years...
__________________
The world takes on a whole new perspective when viewed from 100' below...
1972 Bertram 'Bahia Mar' 20
2006 Mercruiser 4.3MPI (OW617679) w/Alpha 1 Gen II (OW829301)
Mariner 4m ignition problem
Re: Mariner 4m ignition problem
Re: Mariner 4m ignition problem
Linear Mode
