6 volt positive ground question

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Is the distributor grounded to the body to complete the circuit,ie earth strap to engine

 

Evil,
The coil connection / polarity thing is mostly irrelevant here, it will just run better connected one way round. For troubleshooting at this level it's much more basic.
The distributor has to earth the wire from the coil intermittently through the points.
So. 1, does the live wire from the coil connect effectively to the one side of the points? 2, does the other side of the points connect effectively to the base plate of the distributor? 3, does the base plate of the distributor connect effectively to the distributor/engine ground? (lucas has a little jumper cable between the two for instance) 4, are the points closing effectively? 5, are they opening properly?
If you carefully check all the above you should be able to bottom out this problem.
I sometimes just jab a screwdriver at the points and short across them. if I get a spark off the screwdriver I know the points are not closing.
Mart.

 

And diodes (therefore electric fuel pumps with diodes across the points), and electrolytic capacitors, audio systems, ammeters, and yes....coils in ignition systems. Coil polarity is important for optimum tuning. You'll still crank and run with reversed polarity, but the spark will travel the wrong direction at the spark plug electrode.

And BTW, polarity doesn't matter to all motors, just the ones with permanent magnets. Most starter motors use a field winding, and will spin the same direction regardless of polarity. Some windshield wiper and heater motors will run backwards when polarity is reversed.

 

If I'm understanding you correctly you are losing connection somewhere between the coil and points?? I just had an old car give me an eduction in this problem. The screw that carried the current from the wire to the coil and the wire to the points past through the dist. body. It was insulated by some kind of cardboard/bakelite type of material. The screw and dist. body had rusted at some point impregnating this insulator with rust, causing a ground. In this case it caused an intermitant miss in any cylinder. Check things very carefully with an ohm meter. ANY reading from this screw to the housing is BAD.

 

I've run into this problem many times and it's USUALLY a problem with the contact points themselves. Here's how I check them with a common test light:
With the points gap open, use a test light to test for currrent at the point where the coil wire attaches to the distributor. YOu said you've already done that and got current...great.
Now, check for current at both sides of the contact points. [points should be open, still] You should have current on one side of the points only. If there is no current on either side, you have a connection problem between the points and the screw on the side of the distributor..
If you have current on one side of the points, roll the motor over until the points close and retest both sides of the points. I'll bet you have current on only one side of the points.
Use a screwdriver to open the point gap, let the screwdriver slip off the points and let the spring pressure snap the points closed again. Do this manuever about 10 times and I'll bet you begin to see a spark.
If so, you're ready to start the engine now. Double check to see if your test light lights up on both sides of the points. it should.
If not, you have a bad contact between the breaker plate and the distributor ground [usually a little, short braided wire going from the breaker plate to the distributor housing] or a bad condenser.
It's also possible your points are burned so bad they'll need to be replaced.
I once got a cheap set of japanese points that simply would not transfer current across them no matter how much I filed them...
I was in the Motel 6 parking lot in Wendover Utah with my 41 Pontiac coupe. I finally ended up filing my old points [with a file, not an emery board or sand paper unless it's all you have...the little grains in the sandpaper can become embedded on the contacts and no current will transfer across the contacts] and they got me home..

 

I've worked on cars for over over 48 yrs and yes the [pos] gose's to your dist.

 

The negative post is connected to the distributor on a negative ground system
The POSITIVE side of the coil is connected to the distributor on a positive ground system.

 

If the coil is mounted backwards, the current flows through the spark plug backwards. Instead of the center electrode eroding, the ground strap erodes. Since the ground strap isn't anywhere near as hard as the center electrode, it erodes substantially faster, thus, rendering the spark plug useless.

 

Just a thought, but do you have power to the coil while you are in the cranking mode, or have you only checked it in the key on mode? Its a simple thing to miss.

 

with points open there should be voltage to the movable side of point,,,wire coil same as batt ...doc

 

This problem was solved long ago guys.. I converted to a 12 volt neg. ground system.. I touched the key and the ol' Plymouth fired right up..EVILT

 

Funny because this thread was well over a year old until someone went back to prove something to someone else...

 

Plez Help Me Get My Grand Father's Car Running.

Does Anyone Know The Correct Gap To Set The Dual Points On A 1955 270 Red Ram Poly ?

Does + Really Go 2 The Distributer?
Ty,
Darby

 

The coil hookup will match the battery ground. Is a '55 Dodge + or - ground? The points are the ground side of the coil circuit. If pos ground car, pos terminal to distrib... and if neg ground, negative side to distrib. If coil is marked "switch and ignition" or such, you need to know what the hell it was made for or*****yze the coil to figure it out.

 

0.017" 28-32 degrees dwell on each set. Combined is in the 40 degree range. Don't have the spec handy right now on "combined"

Put a piece of paper between one set of points, spin the engine over on the starter motor and check the dwell. Switch the paper to the other set of points and check the dwell on that one. 28 degrees is better than 32 in most cases. When the dwell angle gets up near the limit, hard starting is usually the result.