Converting from motorola box to simple coil ignition system

[seattle scott]

In 2010 Frank Acampora posted: It is really quite simple if you already have a points distributor.

Since the engine is a 12 volt engine with no bypass circuit during start, you need a 12 volt coil or a 9 volt coil and ballast resistor. Run blue wire from "I" terminal of the ignition switch to the POS side of the coil. Run NEG side of the coil to the points. That's it!

Note that the spark will be a bit weaker than the CD ignition and surface gap plugs may not fire.

Do not leave ignition on while engine is not running--coil will be energised and eventually drain the battery

CD stands for Capacitor Discharge. Inside the CD box are large capaitors. the points or the electric eye shutter signals a transistor to "Dump" the capacitors into the coil. The advantage is a very quick build of magnetic field and a sudden collapse, resulting in a much hotter spark than the dwell on normal points can deliver.[/I][/I][/FONT].

I have seen others posting the same information. So I have a 1977 85 hp Chrysler with a points distributor and a failed Motorola cd box. I bought a 12 volt car canister coil that did not require an external resistor. i wired the blue ignition wire to the Pos on the coil and ran a wire from the neg coil post to the points terminal on the distributor and installed the original coil wire in the coil. With key on I get 12.4 volts at the + post on the coil - didn't check the voltage with the starter cranking. I swapped out the surface gap plugs for the regular kind and put a condenser on the distributor post, where the wire form the neg post on the coil is connected. I did not mount/ground the condenser. Anyway with the spark plugs out and grounded I get no spark. Have I wired this up correctly? If I put the voltmeter probes on the coil terminals and crank the engine should I see 12 volts when the points close? I haven't done anything about the points, it looks clean but I haven't checked the gap.

Again, thanks to Frank for helping me get my 135 hp running.

 

[Nordin]

Re: Converting from motorola box to simple coil ignition system

You have to ground the condenser, it shall be parallell with the points. Check that the distributer is well grounded.
One groundwire at the mountingbase and one at the svivel of the distributer (just above the cap).
The grease in the svivel will isolate from ground.

 

[seattle scott]

Re: Converting from motorola box to simple coil ignition system

Nordin, how do I ground the condenser "parallel with the points" , as in where do I attach it. I have the distributor ground wire in place. Thanks.

 

[Frank Acampora]

Re: Converting from motorola box to simple coil ignition system

The negative coil terminal must be attached to the points terminal on the side of the distributor because: With the points closed, current must flow from the blue wire through the coil to ground. This is what builds the magnetic field. When the points open, current stops flowing and the magnetic field collapses, inducing a high voltage pulse in the secondary windings of the coil.

You must also be certain the blue wire is connected to the "I" or "A" terminal of the ignition switch. This terminal only has power when the switch is in run or start position. It delivers power to the coil.



As Nordin said, the condenser MUST be grounded by bolting it to some part of the distributor--otherwise it is doing nothing after the first charge. The condenser serves to absorb voltage flow when the points open, reducing sparking and increasing points life. Instead of trying to jump the gap as points open (producing a spark at the points) voltage flows through the easiest route which is into the condenser.

 

[Nordin]

Re: Converting from motorola box to simple coil ignition system

As Franks says the condenser act as an accumulator for the current. It kick back the current to the coil primeside when the points open and inducing a current in the secondaryside of the coil. It also prevent the points from arcing when it opens.

Mount the condenser at the distributerhousing and connect the wire to the terminal at the distributer. The points is also connected to ground by the mounting inside the distributer and the terminal at dist. They are now connected parallell in the circuit for the primeside of the ign.coil.

 

[seattle scott]

Re: Converting from motorola box to simple coil ignition system

Thanks both of you. Still no spark. I have the blue wire to the "I" terminal on the key switch and also to the Pos on the coil. I get 12.4v on the Pos coil post with key on. Neg post of coil wired to dist terminal with the condensor also on the post and now I have mounted/grounded the condenser to the distributor. The distributor has the normal ground wire from the dist housing to the distributor mounting arm. I installed normal spark plugs and they are out and grounded. With the #1 piston at TDC the line on the distributor pully wheel faces the flywheel with the dist in the throttle closed position. The flywheel is rusted so I haven't found any timing marks on it yet but I know how to "count the teeth" to find the 32 before TDC when WOT.

So should I be looking at the point gap as my next troubleshooting step and set the gap at 0.014?

 

[Nordin]

Re: Converting from motorola box to simple coil ignition system

Yes, clean the points and reset the gap to 0,014 in. If you have a VOM, check the resistance from neg.post at coil and ground with the condenser not attached. The resistance shall go from zero to infinity when turning the pully as the points close and open.

If you have the condenser attached you will charge it with the internal battery in the VOM. This gives you wrong measurments.

SOO you have to disconnect the condenser when you measure the resistance.

 

[seattle scott]

Re: Converting from motorola box to simple coil ignition system

I re-gapped the points from about 0.010-0.012 to 0.014. The points looked new - rotor is clean. The coil won't fire. Stuck a spark plug wire with a grounded plug in the coil - cranked engine - no spark. I have a VOM. What range do I select on the ohms scale I have 5 sections from 200 to 2000k.
If the resistance doesn't change then what am I looking for?

 

[Nordin]

Re: Converting from motorola box to simple coil ignition system

You shall use the lowest range ....200. When the points is closed you would read 0,0-0,5 ohm if it is ok. When the points open you would read infinite. If you have an analog VOM (with a needle, no digit), the needle suppose to turn left to zero.... points close and when it is open ..... nothing just stay all the way to the right.

SOO your question about if the resistance do not change. The Points is bad. BUT if the resistance is low ....about zero (points closed) and not change when you turn the pully, you have to look for a bad isolation at the points.

 

[Frank Acampora]

Re: Converting from motorola box to simple coil ignition system

Assuming the condenser is still attached to the points and the body is grounded: Replace the condenser with a known good one. A shorted condensed will prevent spark. AND with condensers, even a brand new one can be bad--that is why with old school auto ignitions, when doing points replacement, if the condenser was good, you never replaced it with a new one.

 

[seattle scott]

Re: Converting from motorola box to simple coil ignition system

Thanks again to both of you. I will check the points resistance. I did crank the motor with an ungrounded condenser. Also I don't think the condenser is matched to the coil. I had a part number for the coil from another posting on this application, so the auto store guy could give me that, but when asking for a condensor he asked what car and I said no car an outboard motor, just give a condenser that looks like this and I showed him a web post photo.

Also if I replace the points, am I limited to the specific application meaning $35 outboard points, or is there a car points that will work?

Hope you are staying inside today - Frank. Rain in Seattle.

 

[Frank Acampora]

Re: Converting from motorola box to simple coil ignition system

I never tried looking for replacement points. They do seem to be special and specific to Chrysler outboards in their mounting. However if you can find a set of points that fits and mounts inside the distributor and contacts the cam---points are points, a simple open and shut switch.

 

[seattle scott]

Re: Converting from motorola box to simple coil ignition system

Well the resistance/points test was inconclusive. Maybe my meter is bad. With the meter on 200 ohms and the condenser disconnected and probes on the neg coil post and the other on ground and key on and assistant turning the flywheel by hand, the meter showed the digit "1" and didn't change.

What about the test where you disconnect the neg wire at the distributor and pull the coil wire end out the the distributor and tap the small wire ( use to be the white/black wire) to ground while trying to get the coil wire ( the high voltage one) to jump the gap to ground?

 

[Nordin]

Re: Converting from motorola box to simple coil ignition system

Check the VOM by touch the probs to each other. Now it will show "0" zero, remove them and it will show "1" maybe. VOM shows different depending on brand. My Fluke shows "OL" in open circuit and 0,0 in closed circuit.

Try this:
Turn the flywheel soo the curveline at the pully lines up with the rimm of the flywheel. Now the rotor shall point at #1 cylinder hightension wire. The throttle shall be in idle position/timing retarded as much as possible. Disconnect the white/black wire from distributer, screew out "1 plug and ground it. Turn the ign.key to ON position and scratch the white/black wire to engine ground. Now the plug should spark if everything is okey.
When you scratch the wire to ground you simulate the points open/Close action.

 

[seattle scott]

Re: Converting from motorola box to simple coil ignition system

Thanks Nordin. More stuff to do this weekend.

 

[seattle scott]

Re: Converting from motorola box to simple coil ignition system

Nordin, I did your test and I get the #1 plug firing and get a nice spark on the white/black wire when I tap the wire to ground. Sooo, coil is good, coil wire is good, rotor is good and spark plug and wire are good. So it's either a points issue or a condenser issue - correct?. I will replace the condenser since I can get that up the street, and report back. A little progress is better than a poke in the eye.

 

[Nordin]

Re: Converting from motorola box to simple coil ignition system

Seattle scott that?s right.
If you ground the condenser and connect the wire from the condenser to the white/black wire and then scratch/tap the white/black + wire from condenser to ground. If #1 plug fire then the points is bad if not the condenser is bad.

As you said before the VOM did not change in resistance value when you turned the pully. The points is in no good condition.

 

[seattle scott]

Re: Converting from motorola box to simple coil ignition system

Does anyone see any issue with these points or can they fail and still look good?

 

[seattle scott]

Re: Converting from motorola box to simple coil ignition system

Does anyone see any issue with these points or can they fail and still look good? View attachment 221722

 

[Frank Acampora]

Re: Converting from motorola box to simple coil ignition system

Clean the distributor terminal screw. If necessary, replace it with a standard screw--it doesn't need to be knurled. That rust on the screw and nuts is a high resistance connection--can't be helping.