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Subject: 48 8n no spark

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mike    Posted 10-24-2017 at 07:50:37 [URL] [DELETE]        [Reply] [Email]  
  • 48 8n no spark
  • so completely rebuilt tractor sat over the winter but fired off first try this spring and ran without complaint. She doesn't run too often mostly show and little light brush hogging.

    When I went to start her the battery was dead. Installed new battery and no spark a the plugs or distributor. Any suggestions would be greatly appreciated. Thank you.

    Tony    Posted 10-24-2017 at 11:29:13 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 48 8n no spark
  • Bruces' post is as comprehensive as any I have read in a long time. Below is a kinda qwik chek before you dive in deep.

    Front mount or side mount?

    First check which is sometimes overlooked. Current to the primary side of the coil. Switches fail, wires break, resistors fail. No current? Bridge the resistor or hot wire the primary side from the battery. You won't hurt anything bypassing the resistor one time.

    If you have current to the primary side of the coil it might be as simple as opening the points and cleaning them off. Sometimes for some inexplicable reason after a long lay up they get an insulating coating on them particularly in humid climates. Check the tang on the rotor. Make sure it contacts the center post of the cap. Simple stuff first.

    Or..........Key on, current to primary side, high tension lead from coil off the distributor and close to ground, use a small screwdriver to open and close the points. Be careful not to bridge the points or touch the housing with the screwdriver. Should get a hot spark to ground from the coil high tension lead. Or simply roll the engine over with the starter. No spark, points and precautionary condenser a possibility. Check the resistance of the coil or try a known to be good coil. Coils are pretty tough and long lived unless they have been overheated many times. On a front mount it's easier if you remove the distributor, ground it to the tractor, etc. and......front mount coils are said to be less reliable. I dunno.

    Re read Bruces' post it has a ton of useful information. I did.

    Bruce (VA)    Posted 10-24-2017 at 07:57:41 [URL] [DELETE]        [Reply] [Email]  
  • Re: 48 8n no spark
  • 6v or 12v?

    " no spark at the.....distributor. "

    What does that mean? Voltage? Do you have a multi-meter?

    Assuming that the bushings & advance weights are ok (*see below), & that you have correct voltage to the coil (Do you? battery voltage with the points open and about half that with the points closed), the most common electrical failure (no spark, weak spark) points on the front mount are below. Check each one carefully. Pay particular attnion to # 9. Even if you find a problem, check all 10:

    1. The insulator under the brass concave head screw & where the copper strip attaches. (it's fiber & will wear out; poke & prod w/ your meter leads to make sure it still works) If you need to replace the insulator, use a
    .250 x 3/8 nylon square nylon anchor nut available at most big box home stores.

    2. The pigtail at the bottom of the coil not making contact w/ the concave head brass screw inside the distributor. (With the coil on, the pigtail must firmly contact the brass screw. No contact = no spark) Check for continuity between the top of the coil and the pig tail; a 6 volt coil will be around 1 ohm & a 12 volt coil should be 2 to 3 ohms.

    3. The copper strip is broken or grounded to the plate. (look very carefully for cracks & breaks).

    4. The condenser wire grounding to the plate or side of the distributor.

    5. The tab on the bottom of the coil not making contact w/ the brass button on the cap. (With the cap on, the tab must firmly contact the brass button. No contact = no spark.) Check for continuity between the top of the coil and the tab; you should see about 6k ohms.

    6. Incorrect positioning of the spring clip on the plate causing the pigtail to ground. (the open part of the clip goes between 7 & 9 o'clock on the plate. That puts the straight part of the clip opposite of the timing screw at 3 o'clock)

    7. Incorrect seating of the coil on the distributor due to a loose bail or no gasket.(the coil must not move at all; if it does, replace the gasket or bail. Or stick some cardboard under the bail).

    8. Water/moisture inside the cap due to gasket failure or the absence of a gasket. (the cap AND coil have gaskets)

    9. Dirty/corroded/burned/incorrectly gapped or misaligned points. I use only Wells, Blue Streak or Echlin brand points (* *see below). If you are using quality points and cannot get the gap to open to .015, chances are you need to replace the bushings. If the shaft has any sideways movement AT ALL, the bushings must be replaced. (*** see below) If the tractor has been sitting unused for a few points, itís highly likely that the points are glazed. Dress them with brown paper or card stock. With the points closed, you should have continuity between them; high resistance means they are glazed.

    10. Burned rotor, cracked/carbon tracked cap.

    After find the problem & re-check the point gap, do a continuity check before you put the distributor back on the tractor. Before you start, make sure your meter/light works.

    With the distributor still off the tractor, follow these steps:

    1. Coil off, cap off, points open. One probe on the brass screw & the other on both sides of the open points. On the side closest to the cam, you should have continuity. Not on the other side! If you do, you will also have continuity everywhere because the points are grounded.

    2. Coil off, cap off, points open. One probe on the brass screw & the other anywhere on the body of the distributor. You should have no continuity! Now, rotate the tang on the distributor....as the points open & close, you have continuity (closed) and lose it when they open.

    3. Put the coil on the distributor, cap off, points open. One probe on the lead on the top of the coil, the other on the cam side of the open points. You should have continuity!

    4. Coil on, cap off, points open. One probe on the lead on the top of the coil, the other anywhere on the body of the distributor. You should have no continuity!

    At this point, I just put the distributor, coil & cap all back on the tractor as a unit. The reason I do this is because it is real easy to get the cap or coil misaligned trying to put it back together, one piece at a time. The result is something gets broken or you get a 'no spark' problem.

    It's possible to put it back on wrong & break it. Look at the slot on the end of the cam shaft. Whatever angle it happens to be, turn the distributor tang to match it. Make sure you can tell the wide side from the narrow side on both the cam & distributor! (close counts). Place the distributor on the front of the engine, gently push it in place & slowly turn the distributor body until you feel the tang slip into the slot. Rotate the distributor body until the bolt holes line up. Hand tighten the two bolts until the distributor body is flush with the timing gear cover.

    * Unscrew the plate hold down screw & remove the C clip to get the plate out. Remove the shaft & weights. The weights should freely move.

    ** NAPA part numbers:

    . Points: FD-6769X or ECH CS35

    . Condenser: FD-71 or ECH FA200

    . Rotor: FD-104 or ECH FA 300

    . Cap: FD-126 or ECH FA 350

    ** Yesterday's Tractor kit:

    Premium Blue Streak points (A0NN12107ABS), rotor, condenser, and gauge Part
    No: APN12000ABSR

    ** Just8N's kit:

    Heavy-Duty Point Set, Condenser, Heavy-Duty Rotor, Heat Range Matched Spark Plugs. Packed 6 to Master Carton. Contains: 1-9N12107 Point Set, 1-AONN12300A Condenser, 1-9N12200 Rotor,1-9N12104 Gasket Kit,4-AL437 Spark
    Plug,1-015 Gauge, 1-025 Gauge.

    ** Distributor cam lube, Mac's Auto Parts:


    ** Distributor cam lube NAPA:


    *** There are three ways to replace the bushings in a front distributor:

    1. Buy new bushings (part numbers 9N12120 front & 18-12132 rear). Press out the old ones, press in the new ones and ream to fit. CAUTION: do not try this unless you have a press & know how to use it. If you break the base, a new one costs $130. If you bend the tower which holds the front bushing, a new plate will cost you $30. Resist the temptation to buy a new plate; most are pot metal and the threads will wallow out about the third time you change the points.

    2. Take the new bushings and distributor to your local machine shop.

    3. Send the distributor out for bushing replacement if you do not have a local machine shop

    mike    Posted 10-24-2017 at 11:46:43 [URL] [DELETE]        [Reply] [Email]  
  • Re: 48 8n no spark
  • Thanks, Bruce and Tony. It's a 6V system with front mount distributor. The entire system was rebuilt from the ground up, new distributor, points, condensor completed 1.5 years ago. She's run well every time until now and has very few hours. My guess is under 50 hours since rebuild. I will follow up after I figure this out. I appreciate your counsel.

    Bruce (VA)    Posted 10-24-2017 at 16:04:04 [URL] [DELETE]        [Reply] [Email]  
  • Re: 48 8n no spark
  • In the right conditions, points glaze over in 3-4 weeks of non-use.

    mike    Posted 10-24-2017 at 11:43:40 [URL] [DELETE]        [Reply] [Email]  
  • Re: 48 8n no spark
  • Thanks, Bruce and Tony. I will follow up after I figure this out. I appreciate your counsel.

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