M5 wiring switching from diesel to gas

[Tony Nobach]

I have put a gas motor in a diesel tractor and I need some help in figuring out the wiring. I have a new ignition switch that has the following terminals BAT IGN STARTER and ACC. I will not be using the acc part. I have hooked a wire from BAT to 12V. I have a wire from START to the solenoid. The motor will turn over. I assume the IGN terminal is for a wire to the + side of the coil. Do I need to use a resistor in line with this wire to the coil or is 12 volt ok. It was a positive ground and will now be a neg. ground. Will this change anything? I will be using a GM alternator with an internal regulator and I need to know how to run the wires. Where does the 12v wire that goes to the terminal on the back of the alternator come from? Also looking at the back of the alternator the 2 terminals for the regulator are marked 1 on the left and 2 on the right. What wires and where do they come from go to these terminals? I also have a 12V wire from the hot side of the soleniod that goes to a terminal on the amp meter. Maybe I dont need this? Where does the other wire for the meter go? I know this is pretty basic but am sure some of you professionals know what to do. Also there are 2 wires that run from the oil pressure switch. 1 is a ground and 1 went to the old ignition switch. What was the purpose of having power to the oil guage? Thanks for any input

 

[rvirgil_KS]

Whether or not you need a resistor depends on the coil. If it is a 6 volt or a "12 volt external resistor required" coil yes you need the resistor. If it is a "true" or "direct" 12 volt coil no resistor is needed.

Changing positive to negative ground you will need to reverse connections on ammeter. - terminal on coil goes to distributor. Starter, lights, etc. don't care. If it has a fuel gauge those connections may need to be reversed.

With GM alternator with internal regulator. I would run a 10 gauge wire from big output post on back of alternator to one side of ammeter and 10 gauge wire from other side of ammeter to battery side of start solenoid.

#2 wire from alternator plug can loop down to large output post.
#1 wire from alternator plug goes to the coil side of the switch. Add a diode in this line (marked end of diode to alternator) or engine may not shut down when switch is turned off.

BAT post on ignition and light switch should connect to alternator side of ammeter.

To check ammeter connections, turn on ignition and/or lights, engine not running. Ammeter should show slightly negative. If it shows positive reverse the ammeter connections.

Here's a link to my MM diagrams that may help.
MM Diagrams

 

[karl f]

alternatively to the diode, you could run the alternator #1 terminal to the ACC post of the ignition switch. The ACC and IGN posts are electrically separate, so when the key is off, there is no backfeed.

Also, this way, if you decided to wire in a warning light, it would light in the ACC position as a reminder to turn the key off.

Many right ways to do this, and 100 more wrong ones

karl f