312-8 won't start

[wrightorchid 261]

I finally had some time to work on the tractor.  The latest fix was to replace the ignition switch.  The old one was very  fried on the red wire connection, and the only way I could start it was jumping with a screwdriver across the posts.  
I bought a replacement switch, and a pigtail, along with some marine crimp connectors.  The leads from the tractor were very short, but was able to make all of the connections.  I put it all back together, and now no start.  When I turn to run, the lights can be turned on and volt meter activates.  There is nothing lighting on the indicator board, even if I do the test button.  This used to work.  I have plenty of oil in the engine.  When I turn it to start, the voltage drops to zero, and the lights go off.   No sound at all.  I tried to jump but it just turns over.  There have been some switches bypassed by a previous owner.  I need to get back to mowing and moving stuff.  If I could replace the entire wiring harness that would be great, but I am sure it is not an easy task.

Thanks for your help.

Mike

[buckrancher 2,694]

what motor do you have a K or M kohler? and when you got the new switch are all the letters by the terminals the same  and in the same place because it makes a differance on which motor you have

Brian

[wrightorchid 261]

I'll have to double check the switch.  It is a Kohler Magnum 12.

[wrightorchid 261]

I have tried to see which is the correct ignition switch, as there are two that are listed on parts tree and on toro.  Also will need to know the correct drive belt, since there are also several listed.  it is 

Mower 31-12K802  1991   with the M12 motor.

Serial 1032024

[gwest_ca-(File Mod) 11,388]

Original tractor parts list
http://www.wheelhorseforum.com/files/file/2390-tractor-1991-310-8-312-8-ipl-wiringpdf/

Garry

[wrightorchid 261]

It looks like I had the wrong switch, well one with a different number, as I ordered it about 4 years ago..  A new one ordered, so we will try again.
Thanks gwest_ca.
 

[wrightorchid 261]

It turns out I had the correct switch, but did not have a way to verify.  I ordered a new 103991 switch, and confirmed the older one was the same. 
I am able to get it to start, mostly.  If I turn the switch to start, and back off a smidge, to get the right spot.  This does not seem normal.   Returning the key to run and it dies.   If I try jumping the starter with a screwdriver, it turns over, but does not start.  

I am getting 11 v on the battery, and also across the starter solenoid.  I have gauges, and lights, but no indicator board (including the test).  I have looked at my old switch, and it looks like all of the colored wires are going to the correct locations.  Many of the other connections look pretty old and brittle.
The only real difference that I can see is that there are 2 RED wires going to the ignition switch, but  on  pg 107 of the tractor parts list posted by quest_ca, it looks like there would only be one. 

[wrightorchid 261]

Any thoughts?  I'm running out of ideas and things to check.

[gwest_ca-(File Mod) 11,388]

You should have more than 11 volts. Bad battery?
Did you instal the new switch? Perhaps moving the switch it finds a location that provides a bit more current - cleaner contacts.

If you follow the red wire in the diagram you will see a dot where a second red wire attaches. You don't have the indicator lights and test switch or were they removed? Or are they not working? You don't need them to operate the tractor.

Here is the operator manual that explains the safety switches
​
Garry

Edited May 31, 2015 by gwest_ca

[wrightorchid 261]

If the safety switches are working, to allow it to start, what would cause it to immediately shut down, when in run position?  I have continuity on the switch in the proper positions, and the wiring is correct.  This does not make any logical sense.

[gwest_ca-(File Mod) 11,388]

Something is grounding the ignition wire to shut it off. The ignition is self powered and will operate until the ignition wire is grounded.

There are 2 safety switches in the ignition circuit.
The pto when OFF takes the seat switch out of the circuit.
The pto when ON adds the seat switch which will ground the ignition wire if the operator falls out of the seat which closes the seat switch completing the ground of the ignition wire.

Garry

[wrightorchid 261]

If pto is off then the seat should not matter until pto is activated. So it should still run is my thought. Where can i get a stray ground?
 Indicator board is there just not working.  I dont care if it is or not for now.  Pto off, clutch in, in seat.  Should stay running

[gwest_ca-(File Mod) 11,388]

I have seen the plastic insulation on the wires worn so thin and neat that the wire will break the surface in a very small area where it is rubbing on something. That is all it takes and when you look at it it may look like a pencil line on the plastic but it is exposed wire. You can't even feel it so look anywhere the wires are close to something. It may be the steering shaft or just a flat piece of sheet metal where years of vibration has done a number on it. The cheap flexible split wire loom that is available today is great to protect the wires from abrasion.

It has always been said the indicator circuit board does not affect the operation of the tractor but just in case unplug it. Stranger things have happened.

Garry

[wrightorchid 261]

Thanks for y our suggestions.  I will disconnect the board, just in case.  Having lots of bad weather, so will try again later.

[wrightorchid 261]

No change.  I will have to find the bad wire.

[Solex 27]

Make sure to check the two PTO switches and that they a operating properly. They have metal activators that break off with use. If they are not operating correctly they can prevent the engine from turning over and will kill spark to the engine. I have experienced several no spark issues and the PTO switch is a common problem.

[wrightorchid 261]

It is running again.

[gwest_ca-(File Mod) 11,388]

That is good news. What was the problem. I am sure your answer will help others in the future.

Garry

[wrightorchid 261]

It turned out to be an issue of me wiring the switch connector the wrong way.  I thought I had the same perspective, but until I had the switch, and the connector facing the correct way, as they would be plugged in, It was then pretty obvious it was wrong.  I had also contacted Save Old Iron, and he had some additional info on trouble shooting.  Here is what we discussed.  I also cleaned all of the connections, and did a quick search on the Packard/Delphi 56 connectors, so I could understand how they work, and can be taken apart.  It's easier than you would think.  I also charged the battery, as it would not fully engage the starter. 

In a nutshell, I could get it to start, but then would die in the run setting. 

Here is what we discussed
from SOI

My first suggestion is inspecting the white kill wire thru its entire length.
The melt down within parts of the harness is a major concern.

The other thought going thru my head is how any other terminal of the ignition switch could be interfering with the "M" terminal. My plan would be to use the test light to test for a GROUND, not a 12 volt power source. I can fully understand the "M" terminal being grounded in the OFF position and killing the engine. I am not so certain how or why the "M" terminal could be grounded in the RUN position. If that were true, the "B, A, and R" terminals would all be grounded since they are all electrically connected together in the RUN position. This fact would cause the main fuse to blow in the harness.
My theory is the magneto may be getting battery voltage applied to it in the run position, causing the mag to stop sparking and somehow not being destroyed. A theory we can prove or disprove rather easily with the test light.

Tractor not running
Ign key in the OFF position
PTO off

Disconnect the WHITE wire from the magneto assembly - the magneto has a male terminal sticking out of the body. The white wire has the female part of the connection and should pull off the terminal without much force.

Connect the test lite alligator clip to the battery POSITIVE terminal -yes the battery (+). In this configuration, the test lite will light when it touches a GROUND connection.

Touch the test light probe to the female terminal on the white wire removed from the magneto. The test light should light. We have a ground connection.
Do not touch the test light probe to the magneto male terminal - magneto damage could result

Now the interesting part.

Tractor not running
Ign key in the RUN position
PTO off

The ignition switch should remove the ground connection from the "M" terminal and with the PTO in OFF, no electrical connection to the kill wire should exist to any part of the electrical system.. Test the female kill wire terminal again with the test light. The test light should not come on.

If the test light does not come on, the possibilities are the "M" terminal is not grounded (they way the switch should be)

BUT,

this does not rule out the kill wire is not attached to the battery voltage.

To test for this possibility, simply switch the test light alligator clip to the battery NEGATIVE terminal and touch the test light probe to the kill wire female connector once again.
If there is a positive voltage on the kill wire, the test light will shine.
If the test light does not shine, neither a ground or positive voltage is present on the kill wire. This, of course, is what we are hoping for.

Let me know how this works out.

Here is my overall approach.
Begin with the kill function and protect the magneto.
Get the engine to run in RUN.
Move on to checking the charge system.
Confirm accessories work.
Finish with safety functions - seat and PTO.


 

[Save Old Iron 1,568]

Glad to see the issue is sorted out. As w discussed, when faced with multiple issues, pick one issue to start with and work it thru. Most often, the other problems will be corrected in the process.

Now on to checking the charging system.

p.s  Count yourself as incredibly lucky the magneto was not damaged.

[wrightorchid 261]

I do count my self very luck on the magneto.  I hear they are very expensive.  I double and triple checked, but still got it wrong.

[Save Old Iron 1,568]

Looking back on this experience, what question could we have asked to clear up this confusion with the terminals?

[wrightorchid 261]

Since I thought I had the switch wired correctly, I had already ruled this out.  When the test to see if the white M wire was carrying voltage was hot, then looking at which terminals were connected on the switch for each position ( off, start, run), did I realize the mistake in my wiring.  Also, since I was previously able to run engine, but not later, there had to be a difference from before. I am sure it did not hurt to clean all of the connectors while I was at it.  The connectors are simple, but I did not understand the simplicity of the packard terminals in the plastic parts.  It would also be simpler if the M line was white from the switch to the engine.   The pigtail connector to the switch already had the wires in it.  I did not know how to remove them until later, so I had to write down and properly map the color for each line.  

If the weather clears, I'll finish the tests we were doing.

I certainly understand how important it is to have connections correct, because as kid my dad was restoring a 1937 ford business coupe, with a new wiring harness, had a wrong connection, and it fried one of the wires in the loom.  This was a reproduction harness, with the pretty woven fabric covering for the whole car.  This was a very expensive replacement.

[brushbuster 0]

I have pretty much the same thing going on with mine. I can start it by jumping the solenoid, it runs for less than a minute and then shuts down. I was going to replace the switch, but I am not sure that is it. Looks like i will run down all the wiring looking for grounds and worn out wire. Pretty maddening.

[wrightorchid 261]

Good luck, follow the steps, and verify good connections.  Make sure you have the correct wiring diagram.  The Packard connections do come apart.