Mon Sep 13, 2004 10:15 pm

I just purchased a 1952 PO said it was running good and he let it set up
for about 3-4 months and now it will not fire. This CUB has a 6v system
with a distributor and coil. I have checked the following with the indicated

1). Compression [dry] 95 lbs.

2). checked wiring; found defective ign switch [ high resistance open]

3). Found plug wire with defective end [distb end] - repaired

4). Checked and re-gapped plugs

5). Replaced the points and condenser [gapped to .020]

6). Check for voltage [with lead on + Batt post]
a. 6v on either side of coil
b. 6v in coil output to distributor
c. 6v to center contact inside of the distributor cap

7). Checked the wire from the condenser to the point
a. Not shorted to distributor housing or inside or to the
condenser case
b. Post through the distributor housing is insulated

8). Replaced the rotor cap

9). Took coil off another tractor and put on '52 with no change then
replaced on other tractor and made sure it is still good. The donor
tractor started fine.

10). I do get an arc when the points are broken.

Is it possible the plugs are not grounded in the head? I should also say
that the dealer working on this CUB before me connected the Batt
negative to ground. I think I read someplace that this could destroy the
voltage regulator. Could this be happening? I burnished the points on
the relay going to the "L" terminal.

Any help is welcomed.

I am just about to my rope's end on this one. :? :? :? :?

Mon Sep 13, 2004 10:37 pm

Russ, when you crank the engine over does the 6 volts on the lead between the coil and distributor swing from 6 volts to 0 volts (points opening and closing)? Do you get a spark from the coil lead before it goes to the distributor?

at rope's end

Mon Sep 13, 2004 10:49 pm

My thought is that you are not getting voltage to the coil when the engine is cranking. As John suggested check the voltage at the coil when cranking the engine.

Second suggestion is to create a jumper from the battery to the coil then crank the engine. If the engine starts, you have a wiring problem.

Mon Sep 13, 2004 11:39 pm

Thanks John & Eugene,

These are great suggestions. I will do further testing tomorrow. I
have not tested the coil to distributor lead to ground nor have I tested
the swing in voltage at the coil. I assume test the coil at the (-) terminal?

Tue Sep 14, 2004 7:46 am

If it is 6 volts + ground the + lead of the coil should go to the distributor. At that lead you should have 6 volts when the points are open, and 0 volts when they close. If it shows 6 volts all the time, check for oil or corrosion on the points keeping them from making a good contact, or the lead itself being open. If 0 volts all the time, check for shorted condenser, stuck points, shorted insulator on side of distributor, or open coil. You can easily watch the swings by connecting the voltmeter and turning the engine with the crank.

Tue Sep 14, 2004 8:53 am

I think you nailed it John. While I was thinking about it, you put it into words.

Tue Sep 14, 2004 10:08 pm

Thanks again for the speedy response. Here is what I have done this
evening with findings/results:

1). inspected the points, I just install them new Sunday-points not pitted
or discolored and they are clean with no oil or any substance on them.

2). the area inside the distb is clean and dry

3). the condenser is not shorted or open

4). the points are definetly making contact and are adjusted to .020
inch for battery ign/distb

5). I can draw a nice "blue" arc across the points with the ign switch on.

6). have measured the voltage on the (-); (+); and the distb output on
the coil while cranking. The voltage does not vary .10v from 6v.

7). held the distb end of the coil wire near [.020-.125 in] from ground
while cranking and no spark.

8). have measured two coils across the terminals [1 to 1.25 ohmns]
from (-) term to distb lead is 7500 to 8000 ohmns; from (+) term
to distb lead is 7500-8000 ohmns

9). the screw through the distb is not shorted to ground [distb housing]

10). the rotor is definetly turning

11). the wiring from the ign switch to the coil and "L" term on the voltage
regulator looks to be 12 ga. as well as the wire from the ign switch
to the (-) term on the coil.

12). I have check and re-checked the wiring schematic for a 6v batt ign
with voltage regulator and aside from the smaller wiring it is exactly
as the schematic. I have checked all wiring and it all has continunity.

13). I check all the plugs and they all have a good ground and the
electrode is insulated on all of them.

I have noticed that the relay at the "L" terminal on the voltage reg is open
and when you manually force the contact closed you get the same "blue"
arc with the same intensity as across the points. I have not checked to
see it this relay closes when you start to crank and if this breaks the
connection somehow to the points.

I would like to have a complete schematic as to how the points fit into
the picture as well as the voltage reg.

I can't believe that this simple DC circuit has me so stumped. What am
I overlooking guys?

I plan to replace all the wiring with awg #10 tomorrow night and see what
happens. I also plan to perform all the above test on the running one with
a coil. However, it does not have the external voltage reg.

Wed Sep 15, 2004 8:29 am

Back to basics
For battery ignition there is a hot (6 volts) lead that goes to the switch. A second lead goes from the ignition switch to the - terminal of the coil. Third lead goes from the + termjinal of the coil to the bolt on the side of the distributor. This bolt is connected directly to the points and condenser.

When the switch is on you should have six volts at the - term of the coil. As the engine turns the points provide a ground at the bolt on the side of the distributor. This results in the + side of the coil changing from 6 volts to 0 volts and then back again as the distributor turns. The coil must be grounded. None of the other wiring counts for getting the ignition to fire. One other note, the condenser is a critical part of the circuit, if it is not the right value, or the case is not grounded the coil will not build voltage to fire.

circuit path is battery - switch - coil - points - ground.

Wed Sep 15, 2004 8:46 am

Russ, as John said, if you have voltage to the coil and the points are making and breaking, you should be generating spark. You mentioned a bright blue spark at the points which indicates that there is a current flow when the points make. However, sparking at the points is bad. Part of the condensor's job is to buffer that current and bypass the points to reduce the arcing. However, I regress - (old age) - If you take a screwdriver and open & close the points with the ignition on, you should be able to take the coil secondary lead and hold it close to ground and draw and arc. If you do not generate a spark doing that, then the problem is in that circuit somewhere.
I would not change all of the other wiring at this time. If you are going to change all of the wiring as part of the rebuild, do it after you have solved the problem not before. That way, if a problem occurs following the wiring change you will know it is related to the changing of the wires and not something that was pre-existing. If you re-wire a non-functioning circuit you may compound your problems.

If you cannot figure this one out, bring it to Cubarama. It would make a great demonstration and discussion presentation. I'm sure we will have plenty of help.