Re: Ignition System Problems

Posted by John T on October 25, 2006 at 07:18:33 from (66.244.90.5):

In Reply to: Ignition System Problems posted by Larry Schmitendorf on October 24, 2006 at 20:33:34:

Larry, Those coils labeled "12 volts for use with (or requires) an external ballast resistor" are in reality 6 volts coils and indeed on 12 volt tractors one is required or the coil will run too hot and the points burn up prematurely.

That being said, the next question is WHAT OHMS BALLAST should be used????? It should generally be near the same ohms as the coils primary (measured between its lil + and - terminals) so a 50/50 12/6 voltage divider is formed. Typical of ballast ohms and 6 volt coil primary ohms would be maybe 1.25 to 2 ohms but iffffffff the ballast is wayyyyyyyyy higher in ohms then the coils primary, a low ignition current and resultant weak spark (especially when cranking) can happen!!!!!

BOTTOM LINE you need the correct sized ohms ballast to match the coils primary winding resistance and most Ive seen are in the 1.5 to 1.85 or so ohms range ifffffffff designed for the old point n condensor ignition systems having coils of the primary resistance mentioned above.

NEXT thing I would suspect is a bad/resistive ignition switch which a simple "hot wire" test will answer. Simply by pass eliminate the ignition switch by running a jumper wire direct from the hot ungrounded battery post to the high input (NOT to coil) side of the ballast n see what happens then??????????? if that cures the problem suspect the switch. With the ignition on and the points closed (if all else is okay) when using a 6 volt coil and an external ballast on a 12 volt tractor there should be near 6 volts on the coils input but if its wayyyyy less suspect a bad switch or the ballast is tooooooo high ohms.

FINALLY I like Olds suggestion,,,,,, A weak battery and/or a weak starter can cause excess voltage drop while cranking which causes a weak spark which by passing the ballast could help (as a band aid approach). Have the battery load tested and if it and the cables n starter switch/solenoid are all okay but theres excess voltage drop on the battery while cranking, the starer could be the problem BUTTTTTTT FIRST I would remove, clean n wire brush, n reattch each n every battery n starter switch/solenoid n starter n ground cable conenction cuz a bad cable or connection can cause voltage drop and a weak starting spark TRY THAT FIRST !!!!!!!!!!!!

John T

Replies:

• Re: Ignition System Problems Wess C 05:17:49 02/04/07 (0)
• Re: Ignition System Problems Larry Schmitendorf 07:43:12 10/25/06 (4)
  • Re: Ignition System Problems Bob 08:17:58 10/25/06 (1)
    • Re: Ignition System Problems John T 08:43:16 10/25/06 (0)
  • Re: Ignition System Problems 55 50 08:17:13 10/25/06 (1)
    • Re: Ignition System Problems Larry Schmitendorf 08:52:01 10/25/06 (0)

Add a Reply Name: E-Mail: Subject: Comments: Optional Link URL: Link Title: Optional Image URL: Email Notification: If you check this box, email will be sent to you whenever someone replies to this message. Your email address must be entered above to receive notification. This notification will be cancelled automatically after 2 weeks.

TRACTOR PARTS	TRACTOR MANUALS

We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]