Another Front Mount Distributor Question

[Jim.ME]

90-01-3125 is a 61-amp, one wire, rebuilt from Wilson Auto Electric. Is the 14+ volts at the alternator output or at the battery terminals?

 

[RWS904]

90-01-3125 is a 61-amp, one wire, rebuilt from Wilson Auto Electric. Is the 14+ volts at the alternator output or at the battery terminals?

Hi Jim,

That’s the one alright. I measured at both locations, same reading.

 

[Mad Farmer]

Latest update in the saga.

Bought an alternator from O’Reilly Auto parts. Had the battery load tested while I was there, all good. Had to swap pulleys as the new alternator‘s pulley was too narrow for the v-belt. Alternator is now outputting 14+ volts, still runs rough over 1/4 throttle. Keeping the old alternator since the core charge was only $12.

Put a battery tender on it and leaving it alone for the evening. I found a new set of plug wires in a box I forgot the previous owner included. If nothing changes when I start it in the morning, I’ll try installing the new wires tomorrow. The only other thing that I know isn’t working at the moment is the ammeter, which hasn’t worked in years. Tractor Supply is 3 miles away and has them in stock for $14, just in case…

Snaking the plug wires through the metal conduit is lots of fun. The wire(s) to the alternator (or generator/reg) and coil wire can fit in there too.

 

[Non-farmer]

Lol, I missed out on that fun. The only things left in my conduit are the alternator and coil wires. If I had thought about it, I would have pulled the plug wires through, before I crimped the cap end on them, with my fish tape. But I didn't so I didn't. They're zip tied to the side of the conduit now. I didn't want to take that adventure.

 

[RWS904]

Happy Sunday everyone! The battery was fully charged this morning, started up and ran terrible, again. Pulled the distributor again to check the point gap, .015 on all four lobes. Did static continuity checks on the coil and didn’t see anything out of the ordinary. Mind you, this coil is 2 months old.

Installed new plug wires and although it wasn’t fun, snaking them through the conduit wasn’t as painful as putting the distributor boots on the wire ends. Mission accomplished, reinstalled the distributor, cap and coil, started up and ran just as poorly as it did before. On a whim, I bypassed the ammeter with no change in running behavior.

I pulled the drain plug from the carburetor and appear to be getting good flow. There was some debris in the sediment bowl so maybe my recently rebuilt carb needs to be cleaned again. I doubt the coil went bad in 2 months time but it’s in the realm of possibility. It’s a good thing this is just a project and not a working farm tractor or we would starve.

 

[old]

Happy Sunday everyone! The battery was fully charged this morning, started up and ran terrible, again. Pulled the distributor again to check the point gap, .015 on all four lobes. Did static continuity checks on the coil and didn’t see anything out of the ordinary. Mind you, this coil is 2 months old.

Installed new plug wires and although it wasn’t fun, snaking them through the conduit wasn’t as painful as putting the distributor boots on the wire ends. Mission accomplished, reinstalled the distributor, cap and coil, started up and ran just as poorly as it did before. On a whim, I bypassed the ammeter with no change in running behavior.

I pulled the drain plug from the carburetor and appear to be getting good flow. There was some debris in the sediment bowl so maybe my recently rebuilt carb needs to be cleaned again. I doubt the coil went bad in 2 months time but it’s in the realm of possibility. It’s a good thing this is just a project and not a working farm tractor or we would starve.

Pull the air intake tube off the carb and fire it up. Place your hand over the air intake briefly as in you don't want it to die. Do it a few times and it may start running right. BTDT many times on my Fords and other tractors

 

[RWS904]

Thanks, Old. I gave that a few tries and it didn’t improve the situation. While I had the intake tube off, I did try a couple brief sprays of starting fluid to see if RPM’s increased or it ran smoother. Didn’t change anything so I’m starting to question the coil more and more.

 

[old]

Thanks, Old. I gave that a few tries and it didn’t improve the situation. While I had the intake tube off, I did try a couple brief sprays of starting fluid to see if RPM’s increased or it ran smoother. Didn’t change anything so I’m starting to question the coil more and more.

Check and make sure you have a good blue/white spark that will jump a 1/4 inch gap or more. I take an old plug and widen the gap to 1/4 inch or close and use that the test spark

 

[Mad Farmer]

Where did you buy the coil from? Some new ones are a POS right out of the box. Does it have proper resistors?

 

[RWS904]

Where did you buy the coil from? Some new ones are a POS right out of the box. Does it have proper resistors?

Bought the one currently installed from Y-T. On a wing and a prayer I ordered one from Amazon that arrived this morning. I’ll test both of them on an LCR meter and post the results here.

 

[HCooke]

I pulled the drain plug from the carburetor and appear to be getting good flow. There was some debris in the sediment bowl so maybe my recently rebuilt carb needs to be cleaned again.

How does the sediment bowl look. When you got good fuel flow thru the carb, was that right after it wqas running poorly? How long did you let the fuel flow? Suggest you let it flow for al least a min. Catch in a clean container.

 

[RWS904]

Good morning all. I tested both the current (2 month old) coil from Y-T and compared the one that arrived from AMZ yesterday on a precision LCR meter. All readings were substantially similar, the two DC resistance readings (primary to primary, primary to secondary) were practically identical (approximately 2.57 ohms on the primary, 12.7kohms to secondary).

Checked the ground strap resistance to the alternator bracket, .3 ohms. Will inspect wiring next and see where that leads.

 

[Jim L WA]

I have a question RWS904, Originally your problem was the tractor would start running poorly after several minutes of running. Now you are saying that whatever you try, it still runs poorly. So, is this after it runs for awhile or as soon as you start it up.
Then can you describe runs poorly?

 

[will-max dairy]

Good morning all. I tested both the current (2 month old) coil from Y-T and compared the one that arrived from AMZ yesterday on a precision LCR meter. All readings were substantially similar, the two DC resistance readings (primary to primary, primary to secondary) were practically identical (approximately 2.57 ohms on the primary, 12.7kohms to secondary).

Checked the ground strap resistance to the alternator bracket, .3 ohms. Will inspect wiring next and see where that leads.

Testing a coil with DC measurements at low voltage is only part of the story. Your measurements are encouraging, but they do not rule out leakage at high voltages and/or temperatures.

A variable spark tester is your friend.

 

[wore out]

Testing a coil with DC measurements at low voltage is only part of the story. Your measurements are encouraging, but they do not rule out leakage at high voltages and/or temperatures.

A variable spark tester is your friend.

A good coil will "ring", that is the basis of how ignition coil testers work.

Even a shorted "turn" or two will show up on such a tester.

The internal short, even though resistance isn't affected much, dissipates potential spark energy as heat.

One of my coil testers, I don't seem the have a photo of the military surplus unit I normally use.

 

[will-max dairy]

A good coil will "ring", that is the basis of how ignition coil testers work.

Even a shorted "turn" or two will show up on such a tester.

The internal short, even though resistance isn't affected much, dissipates potential spark energy as heat.

One of my coil testers, I don't seem the have a photo of the military surplus unit I normally use.

The gold standard for bench testing. I would still put a eleven dollar spark tester on the tractor first, though; especially since the OP is still chasing "fuel vs spark"...

If I had a shop that tested coils on a routine basis...that green gem above would be just what the Dr ordered.

 

[will-max dairy]

A good coil will "ring", that is the basis of how ignition coil testers work.

Even a shorted "turn" or two will show up on such a tester.

The internal short, even though resistance isn't affected much, dissipates potential spark energy as heat.

One of my coil testers, I don't seem the have a photo of the military surplus unit I normally use.

You can probably appreciate this.

About ten years ago in a previous job (not automotive... but electronics)

A low current bias power supply in a piece of electronics. It was supposed to make something like 400V. It made practically zero volts and would go into shutdown mode almost as soon as it was turned on. All components checked out OK for continuity. Some rectifier diodes (little guys, about the size of a kernel of wheat) seemed to have a little brownish crud around them on the circuitboard. Looked suspicious to me. I desoldered them and replaced with new. Everything worked just fine.

Once the diodes were off the board, I wired them to a variable power supply... power supply + to diode - and vice versa... to reverse bias the diodes.

The were rated for something like 750Volts in reverse bias. The circuit was supposed to operate up to 400. The held up to less than 100 volts before they short circuited.... which is what was causing the original circuit to go into shutdown mode... and then look just fine when you measured at DC.

Now... why those diodes failed? I'll never know if they failed and then the circuit failed... or if the circuit experienced an overstress, which killed the diodes...

But... suffice to say... measuring stuff at DC, when it operates at high voltages, is just part of the picture.

 

[RWS904]

You can probably appreciate this.

About ten years ago in a previous job (not automotive... but electronics)

A low current bias power supply in a piece of electronics. It was supposed to make something like 400V. It made practically zero volts and would go into shutdown mode almost as soon as it was turned on. All components checked out OK for continuity. Some rectifier diodes (little guys, about the size of a kernel of wheat) seemed to have a little brownish crud around them on the circuitboard. Looked suspicious to me. I desoldered them and replaced with new. Everything worked just fine.

Once the diodes were off the board, I wired them to a variable power supply... power supply + to diode - and vice versa... to reverse bias the diodes.

The were rated for something like 750Volts in reverse bias. The circuit was supposed to operate up to 400. The held up to less than 100 volts before they short circuited.... which is what was causing the original circuit to go into shutdown mode... and then look just fine when you measured at DC.

Now... why those diodes failed? I'll never know if they failed and then the circuit failed... or if the circuit experienced an overstress, which killed the diodes...

But... suffice to say... measuring stuff at DC, when it operates at high voltages, is just part of the picture.

I would love to have a piece of equipment like Wore-Out showed us. Even if I only used it once, it’s a piece of art to me that would drive my wife crazy seeing it on a bookcase.

As for testing at DC only, the LCR meter I used also tests at (relatively low) AC voltages at frequencies from 100hz to 1MHZ. We use the same device for testing high voltage inductors and transformers. Both coil readings were substantially similar at all AC settings.

Will-Max, you are correct, I’m starting to chase fuel again (in my head) the farther I go down this rabbit hole.

 

[RWS904]

I have a question RWS904, Originally your problem was the tractor would start running poorly after several minutes of running. Now you are saying that whatever you try, it still runs poorly. So, is this after it runs for awhile or as soon as you start it up.
Then can you describe runs poorly?

Hi Jim, the last few cold starts it has run poorly from the time it fires until I shut it off.

 

[Jim L WA]

Hi Jim, the last few cold starts it has run poorly from the time it fires until I shut it off.

I was wondering if that was the case. Double check your firing order since you have replace the plug wires. My manual is out in the garage, but I'm pretty sure it's 1,2,4,3 CCW.