Re: Inconsistant spark/wiring help!

Posted by Tom on October 29, 2003 at 22:57:42 from (205.188.208.73):

In Reply to: Inconsistant spark/wiring help! posted by Dana Maanum on October 29, 2003 at 10:06:38:

Dana,

If you already know the theory behind the operation of an ignition system, please ignore this post. If not, you might want to read on. Sometimes knowing theory can help with practical problem determination.

Coils are comprised of a primay winding and a secondary winding. The primary winding only has battery voltage applied to it. The secondary winding generates a high voltage (20,000 volts or more) that is delivered to the spark plugs. The primary winding has current flowing through it when the ignition switch is turned on and the points are CLOSED. When the points OPEN, the magnetic field inside the coil collapses and induces the large voltage into the secondary winding. This large voltage is delivered from the big center post of the coil to the big center post on the distributor cap. The rotor, inside the distributor cap, then delivers the large voltage to the appropriate spark plug wire which delivers the large voltage to the spark plug. An arc takes place in the center of the spark plug which ignites the fuel/air mixture in the cylinder.

One complicating fact is that the voltage to the primary winding is switched on when the ignition switch is turned on, however, in your case, that voltage goes to the resistor which reduces the voltage to the coil under normal operation. When you turn the ignition switch to the START position, it bypasses the resistor and delivers full battery voltage to the starter solenoid, which engergizes and causes the starter to turn. The starter solenoid also has a small wire running to the primary winding of the distributor. This connection only has voltage on it when the starter solenoid is engergized. When the ignition switch is in the START position, the ignition switch actually disconnects the normal connection from the ignition switch to the resistor.

So, having said all of that, one thing you might check is to insure that you really have battery voltage to the primary winding of the coil when the ignition switch is in the START position. If not, you'll get one spark as a result of having charged the coil when you turned the ignition on, but no more sparks since you aren't getting voltage to the primary when the switch is in the START position.

If that is the case, you might check for a defective starter solenoid or a missing wire from the starter solenoid to the primary winding of the coil. To complicate matters further, sometimes, instead of relying on the starter solenoid to provide the battery voltage to the primary side of the coil during starting, some ignition switches are wired so that a wire runs from the START position of the ignition switch to the starter solenoid AND to the primary winding of the coil. Thus, battery voltage is applied directly to the primary winding of the coil when the ignition switch is in the START position, but then the switch applies the voltage to the resistor in the normal run position.

I hope this hasn't been too confusing.

Good luck,

Tom

Follow Ups:

• Re: Re: Inconsistant spark/wiring help! Allan 02:59:36 10/30/03 (0)

Post A Followup Name: E-Mail: Subject: Re: Re: Inconsistant spark/wiring help! 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 ]