Crazy Distributor

[OldFart187]

On my Ferguson TO30, likely similar to 9N, 8N and many others, I removed the Delco distributor after the tractor was running ok. On reassembly:

1. the flywheel was set to 6 deg BTDC on rhe compression stroke
2. the distributor was installed with the rotor pointing toward the #1 plug
3. the housing was rotated so the points just start to break (coil fires) on the cw side of the cam
THE PROBLEM: Instead of pointing at a cap contact, the rotor points to the space 40 degrees from one and 50 degrees from the other.

The distributor wasn't disassembled
The point gap was set correctly
The centrifugal advance works smoothly
The breaker plate is on snug
The rotor key is intact
The cap only goes on one way and snaps on tight
The 6 deg BTDC setting on the compression stroke was triple checked

Since the housing locks the point and cap location together, indexing the shaft by a gear tooth simply moves the rotor so when you readjust the point break location, the cap moves with it.

Any ideas?

 

[Jim L WA]

2. the distributor was installed with the rotor pointing toward the #1 plug

You want the rotor pointing to the number one tower on the distributor cap. Not the spark plug.

 

[Brown David]

2. the distributor was installed with the rotor pointing toward the #1 plug

You want the rotor pointing to the number one tower on the distributor cap. Not the spark plug.

Was gonna say that but assumed he worded it poorly.

 

[OldFart187]

It was pointed to the #1 plug to put shortest wire in that general direction, really not too important since you can switch wires as needed. The internal cap contact moves slightly when you rotate the distributor to get the points into the firing position. That's when the rotor aims between the cap contacts instead of directly (or nearly) at one of them. If you rotate the distributor so the rotor points directly at a cap contact, the point cam on the shaft is about halfway between the lobes.

 

[used red MN]

The internal cap contact moves slightly when you rotate the distributor to get the points into the firing position. That's when the rotor aims between the cap contacts instead of directly (or nearly) at one of them. If you rotate the distributor so the rotor points directly at a cap contact, the point cam on the shaft is about halfway between the lobes.

Sorry this may be obvious or idiotic, are you using the correct distributor rotation? The housing will be turned the opposite direction of distributor rotation to set it at the proper time of spark. At that position the points rubbing block will be rising up the progression of the cam lobe to the highest point where the points gap is set. Other wise you will have to check that all is correct in the mechanical advance, it would be odd for something to get out of position that far since you claim it was running correctly previously.

 

[OldFart187]

Makes sense, not idiotic at all. I've been known to overlook the obvious so I appreciate any cross checks. The crankshaft rotates clockwise and so does the distributor shaft looking down from the top. Once you install the distributor so the rotor aims at the desired cap electrode, you tighten the tie down screw. At that position, the points should be very near where they start to open. Then, loosen the swivel clamp and rotate the housing slightly clockwise off the cam, then counterclockwise until the points just start to open. The cap will move with the rotation but the rotor and cap electrode should still be pretty close. In this case, they're not.

 

[used red MN]

Makes sense, not idiotic at all. I've been known to overlook the obvious so I appreciate any cross checks. The crankshaft rotates clockwise and so does the distributor shaft looking down from the top. Once you install the distributor so the rotor aims at the desired cap electrode, you tighten the tie down screw. At that position, the points should be very near where they start to open. Then, loosen the swivel clamp and rotate the housing slightly clockwise off the cam, then counterclockwise until the points just start to open. The cap will move with the rotation but the rotor and cap electrode should still be pretty close. In this case, they're not.

Sounds like I agree with that methodology.

 

[soaked]

Did you put in new points, if so is the rubbing block in the identical location as the old set, and not too tall?

 

[OldFart187]

Same set that worked just before it was removed.

 

[soaked]

Could the advance mechanism have come out of its spot, or shifted position when the distributor was out of the tractor, putting the points cam in a funk?

 

[OldFart187]

Thanks. I'll check it out.

 

[Tall T]

On my Ferguson TO30, likely similar to 9N, 8N and many others, I removed the Delco distributor after the tractor was running ok. On reassembly:

1. the flywheel was set to 6 deg BTDC on rhe compression stroke
2. the distributor was installed with the rotor pointing toward the #1 plug
3. the housing was rotated so the points just start to break (coil fires) on the cw side of the cam
THE PROBLEM: Instead of pointing at a cap contact, the rotor points to the space 40 degrees from one and 50 degrees from the other.

The distributor wasn't disassembled
The point gap was set correctly
The centrifugal advance works smoothly
The breaker plate is on snug
The rotor key is intact
The cap only goes on one way and snaps on tight
The 6 deg BTDC setting on the compression stroke was triple checked

Since the housing locks the point and cap location together, indexing the shaft by a gear tooth simply moves the rotor so when you readjust the point break location, the cap moves with it.

Any ideas?

With the points closed but just ready to open, relative to and against the clockwise rotation, before I rotate the distributor counterclockwise,
I turn the key on.
As soon as the just-opening points spark, that's where I lock the distributor body down.

 

[OldFart187]

SOLVED! I think. Although you frequently can't trust AI, two of them said the existing cap is the wrong one. The cap I have has the index notch between two of the electrodes while AI says the correct TO30 cap notch is in line with an electrode. That would explain the problem exactly! The wrong cap puts the point follower on the rotor flat when the rotor points at the cap electrode rather than on the lobe. Apparently the previous owner installed the wrong cap. How it ran like that is a mystery. There must have been some long sparks inside the cap. If anyone with a TO30 could check their cap notch location, that would nail it down.

 

[used red MN]

SOLVED! I think. Although you frequently can't trust AI, two of them said the existing cap is the wrong one. The cap I have has the index notch between two of the electrodes while AI says the correct TO30 cap notch is in line with an electrode. That would explain the problem exactly! The wrong cap puts the point follower on the rotor flat when the rotor points at the cap electrode rather than on the lobe. Apparently the previous owner installed the wrong cap. How it ran like that is a mystery. There must have been some long sparks inside the cap. If anyone with a TO30 could check their cap notch location, that would nail it down.

Do you have the points dust cover or maybe misplaced it? It could be possible that it indexes the cap differently.
YT TO30 points dust cover

 

[Jim L WA]

I was going to ask if it was a new cap or not. I ordered a new cap and rotor (from this site) for my TO-20 that I had and it ran like crap. I ended up using the old ones.

 

[OldFart187]

Good thought about the dust cover. Another possibility. The cap I have looks new, likely replaced just before I got it.