Ford 641: no spark from rebuilt distributor

[drjake81]

The tractor ran like a top the past
couple years. This year it was starting a
little hard, so I decided to replace
points, condenser, cap and plugs. Now I
can't get a spark from the distributor at
all.

I've followed many threads on this site
trying to resolve this to no avail.
Here's a quick summary:

Set new points to .025 on the dot.

Found TDC using the thumb over the
cylinder trick and rotated flywheel to
24? BTDC.

Holding the cam lobe at full advance, I
rotated the distributor counterclockwise
until the points just open and stabbed
the distributor.

Put dust cap, clip, rotor and cap back
on. Grounded #1 spark plug. Key on and
hit starter... NO SPARK.

Moved #1 plug wire from distributor to
capacitor and tested again...GOOD SPARK.

Moved #1 plug wire back to distributor
and loosened distributor bolts. Moved
engine back to 24? BTDC. Grounded #1 plug
again and rotated distributor to achieve
static timing. GOOD SPARK while rotating
clockwise. NO SPARK while rotating
counterclockwise. Tried starter...NO
SPARK.

Given that the cam on the inside rotates
clockwise, I was expecting to rotate the
distributor counterclockwise for static
timing. However, when rotating
counterclockwise, I can here sparks
jumping around inside the distributor and
sometimes sparking where the distributor
meets the block.

I also noticed that one of the contacts
in the NEW cap is worn already indicating
a bushing issue in the distributor. Not
sure if this would cause the symptoms
above. The successful static timing spark
is throwing me for a loop.

Please help!!!

 

[Bob]

(quoted from post at 15:52:23 07/21/19) The tractor ran like a top the past
couple years. This year it was starting a
little hard, so I decided to replace
points, condenser, cap and plugs. Now I
can't get a spark from the distributor at
all.

I've followed many threads on this site
trying to resolve this to no avail.
Here's a quick summary:

Set new points to .025 on the dot.

Found TDC using the thumb over the
cylinder trick and rotated flywheel to
24? BTDC.

Holding the cam lobe at full advance, I
rotated the distributor counterclockwise
until the points just open and stabbed
the distributor.

Put dust cap, clip, rotor and cap back
on. Grounded #1 spark plug. Key on and
hit starter... NO SPARK.

Moved #1 plug wire from distributor to
capacitor and tested again...GOOD SPARK.

Moved #1 plug wire back to distributor
and loosened distributor bolts. Moved
engine back to 24? BTDC. Grounded #1 plug
again and rotated distributor to achieve
static timing. GOOD SPARK while rotating
clockwise. NO SPARK while rotating
counterclockwise. Tried starter...NO
SPARK.

Given that the cam on the inside rotates
clockwise, I was expecting to rotate the
distributor counterclockwise for static
timing. However, when rotating
counterclockwise, I can here sparks
jumping around inside the distributor and
sometimes sparking where the distributor
meets the block.

I also noticed that one of the contacts
in the NEW cap is worn already indicating
a bushing issue in the distributor. Not
sure if this would cause the symptoms
above. The successful static timing spark
is throwing me for a loop.

Please help!!!

"Moved #1 plug wire from distributor to
capacitor and tested again...GOOD SPARK."

I'm gonna ASSUME you mover the plug wire to the center tower of the COIL.


My first GUESS would be the new rotor and/or cap are the wrong part #, or made incorrectly and when the points "break" the tip of the rotor is between high-tension terminals in the cap, instead of right at one of them.

Put the old cap and rotor back on and see what happens and/or VERY closely compare the old parts to the new ones.

 

[drjake81]

Yes Bob, you're right...I moved the plug wire to the coil for that test, not the capacitor.

I think I found the issue actually and you were close when mentioning that the rotor is between the high-tension terminals when the points break.

Upon further inspection of the cam and weights, I found that they were so worn that it was actually retarding the cam (and break point). This lead to the points breaking too late after the rotor had already
passed each contact in the cap. Thus the spark would fire while the rotor was between the contacts.

In looking up the part number I found FAA12176A(Cam and Weight Assy). In the few places I can find this part, it appears to be more expensive that a new aftermarket distributor. I see that the 8N tractors
have a very similar looking part (8N12176) that can be found for much less. Does anyone know if these two parts are interchangeable?

Thanks,
Jake

 

[JMOR]

(quoted from post at 14:09:52 07/23/19) Yes Bob, you're right...I moved the plug wire to the coil for that test, not the capacitor.

I think I found the issue actually and you were close when mentioning that the rotor is between the high-tension terminals when the points break.

Upon further inspection of the cam and weights, I found that they were so worn that it was actually retarding the cam (and break point). This lead to the points breaking too late after the rotor had already
passed each contact in the cap. Thus the spark would fire while the rotor was between the contacts.

In looking up the part number I found FAA12176A(Cam and Weight Assy). In the few places I can find this part, it appears to be more expensive that a new aftermarket distributor. I see that the 8N tractors
have a very similar looking part (8N12176) that can be found for much less. Does anyone know if these two parts are interchangeable?

Thanks,
Jake

o, they are not. opposite rotation. would result in rotor pointing at a point ~30 degrees (amount of dewll) from a plug tower at time points open & coil fires.