How can I check my matchbox?

[Joecey54]

   I was driving to a car show the other evening and while doing some spirited driving my car died. I knew right away I lost my ignition. When I got to the side of the road and opened the hood my coil had come out of the holder and was dangling. The positive side that goes to the dizzy had come off and was touching the negative side of the coil. I was hoping that it wasn't a problem and hooked it back up. Jumped in the car and it fired back up. As it was idling I was looking through my car looking for some zip ties or something just to tie it up to get me home and then it died again.. After looking for about a half an hour I couldn't find any other problems and with minimal tools I called the tow truck.

 

I have now checked all the wiring,coil and coil wire still not showing herself. I thought it was the coil so I tried one I had laying around and still nothing. So here is my question. How do I go about checking the matchbox itself? Ohm it out? what should it be?

or is there something I'm missing I have 12 volts to the coil and it stays while cranking.

 

Any help would be appreciated.

 

Joe

[datzenmike]

Hanging by the wires has probably stretched and broken one under the insulation. Check the plug on the dizzy.

 

You should have 12 volts on the B terminal of the matchbox and the + terminal of the coil

 

[Joecey54]

I thought It broke one of the wires too but I ohmed them out and everything was good.

I have checked the plugs and I haven't been able to see anything.

I have 12 volts at the positive side of the coil and the B terminal, along with that I have 12 volts at the C terminal and the negative side of the coil.

[ggzilla]

There are 12 tests for the matchbox unit itself. See http://datsun1200.com/modules/mediawiki/index.php?title=Matchbox_Testing

[DanielC]

I did this.

 

You need a coil, a spark tester, some wire, and a 12 volt battery.

This is a basic schematic diagram of the wires.

 

 

Hook battery positive up to + on the coil, and the "B" terminal on the matchbox.

Hook the - on the coil to the "C" terminal on the matchbox.

Hook one end of the spark tester to the center (high voltage) terminal on the coil.

Hook the other end of the spark tester to ground.

Check all the connections. 

Hooking the body of the distributor turns it on. 

Turning the rotor should make sparks like my short video did.

[dr.feltersnatch]

hotwire it real quick. this will eliminate any bad wiring and it takes like 2 seconds. run a wire from battery pos to the b side and run a wire from the other side of the matchbox to the neg coil side. be warned you will have to remove these wire for it to shut off, your key wont do it.

[DanielC]

"hotwire it real quick. this will eliminate any bad wiring and it takes like 2 seconds. run a wire from battery pos to the b side and run a wire from the other side of the matchbox to the neg coil side. be warned you will have to remove these wire for it to shut off, your key wont do it."

 

You also need a battery wire to positive of the coil.  You must also confirm that the distributor body is grounded well.

[Joecey54]

I was finally able to work on my car this weekend.

When I checked for power I seem to get 12v on the positive side of the coil and the b terminal. Along with that though I have 12v at the C terminal and the negative side of the coil. That to me doesnt sound right. Does my matchbox have a short in it somewhere?

[datzenmike]

The negative side of the coil will read some voltage coming through from the positive side. Don't forget, the matchbox is really just an electronic switch. It opens and closes a switch to ground on the negative side of the coil. It also has a circuit that senses when the ignition is ON but the motor not turning and leaves the switch OFF so the coil does not over heat.

 

As soon as you crank the motor over the reluctor and stator send a small pulse to the module and it closes the switch and the coil 'charges' up and then the switch opens and the coil fires.

[ggzilla]

It is normal. When the points are open (or the EI ignitor off) the coil will show same voltage on each side.

[datzenmike]

As far as checking the matchbox... why??? Connect it up properly and it should work, then forget it.

[dr.feltersnatch]

If its bad I have a spare I will let go cheap

[ggzilla]

The terminal is broken off - does that make it bad?

[dr.feltersnatch]

In my eyes yes. Will it still work? Maybe but for how long.

[datzenmike]

With some careful work you can remove the back of the module and maybe solder a wire on
 
 

 
 
If I were you, I'd get a General Motors HEI unit from a wrecking yard . Option one... put in back pocket. Option two... pay $15 for a '77 Corvette or equivalent module. Wire up this way... (ignore the 'non matchbox' part.... the red and green wires are the same) If it fails to fire reverse the red and green wires. Mount the HEI on the inner fender where rad air can blow on it. No worries the stock Chev location is at the back of the motor with a distributor wrapped around it.
 
 

Looks like this...

 

 

This is basically a free fix for a troubled matchbox module.