IHC wiring

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   So the cows got at the wiring on an old pumping unit with a 301 engine. Anyone know what goes where? I  need to rewire from the Murphy switch to the distributor. It is 12 volt negative ground with an external resistor. It can't be that hard but I seem to have done something wrong as it tries to fire but is backfiring. Sparkplug wires and timing are correct. Also this is a nat gas engine but I don't think that makes a difference. The distributor only has a single wire going to it and there is a wire that comes directly from the starter that also goes somewhere to the coil or resistor. Any help is appreciated. 

Edited by Acguywill - 14 Jun 2024 at 5:10pm

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Acguywill Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 15 Jan 2024 Location: Vauxhall ab Can Points: 57	Post Options Post Reply Quote Acguywill Report Post Thanks(0) Quote Reply Topic: IHC wiring Posted: 14 Jun 2024 at 4:47pm
	So the cows got at the wiring on an old pumping unit with a 301 engine. Anyone know what goes where? I need to rewire from the Murphy switch to the distributor. It is 12 volt negative ground with an external resistor. It can't be that hard but I seem to have done something wrong as it tries to fire but is backfiring. Sparkplug wires and timing are correct. Also this is a nat gas engine but I don't think that makes a difference. The distributor only has a single wire going to it and there is a wire that comes directly from the starter that also goes somewhere to the coil or resistor. Any help is appreciated. Edited by Acguywill - 14 Jun 2024 at 5:10pm

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steve(ill) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 11 Sep 2009 Location: illinois Points: 78590	Post Options Post Reply Quote steve(ill) Report Post Thanks(0) Quote Reply Posted: 14 Jun 2024 at 8:04pm
	here is a generic drawing of a 12v alternator with a OLD coil and the required resistor to make it work on 12v ... Every coil i have seen has two small wires to it.. You need a HOT WIRE from the key ( maybe it goes thru the murphy switch).... and there should be another wire to the distributor .. ( which is then grounded thru the point). Normally a backfire on an engine that was running good yesteday means that two of the spark plug wires have been switched.. Double check that.. might not be the same as ALLIS... You might run a HOT wire from the battery straight to the Coil and BYPASS the Murphy switch for a test ( not knowing all what the SWITCH DOES).. Normally you have it wired to an ENGINE OIL PRESSURE switch or ENGINE TEMP SWITCH that shuts off the SPARK if something goes wrong... "NORMALLY" you have to hold in a BUTTON while you crank to get it started, then let off after running and you have oil pressure.. Edited by steve(ill) - 14 Jun 2024 at 8:06pm
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steve(ill) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 11 Sep 2009 Location: illinois Points: 78590	Post Options Post Reply Quote steve(ill) Report Post Thanks(0) Quote Reply Posted: 14 Jun 2024 at 9:41pm
	here is the wire diagram for a BASIC Murphy Switch... yours may be more or less complicated... but the TERMINALS on the Murphy should show where the wires go..
	Like them all, but love the "B"s.

Acguywill Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 15 Jan 2024 Location: Vauxhall ab Can Points: 57	Post Options Post Reply Quote Acguywill Report Post Thanks(0) Quote Reply Posted: 14 Jun 2024 at 10:47pm
	Well I managed to get it going. Was a mix of things but mainly a leaky diaphragm on the fuel mixer and a bad resistor. It wasn't getting quite enough fuel due to a leak in the diaphragm so the engine vacuum wasn't enough to open the gas valve far enough to let the proper amount of fuel through. As far ar the resistor the longer I cranked the engine the weaker the spark got even though it was cranking fine. The second wire from the starter is only energized during cranking and basically bypasses the Murphy. As soon as you let off the key that current stops and the Murphy takes over provided that the oil pressure and temperature are good. Thanks for the replies.

steve(ill) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 11 Sep 2009 Location: illinois Points: 78590	Post Options Post Reply Quote steve(ill) Report Post Thanks(0) Quote Reply Posted: 14 Jun 2024 at 10:54pm
	those old resistors are to make an old 6 volt coil work on 12 volts... Do yourselft a favor and get a NEW 12v coil with internal 3 ohm resistance.. and scrap the resistor and Old coil...
	Like them all, but love the "B"s.

steve(ill) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 11 Sep 2009 Location: illinois Points: 78590	Post Options Post Reply Quote steve(ill) Report Post Thanks(0) Quote Reply Posted: 14 Jun 2024 at 10:56pm
	The second wire from the starter is only energized during cranking and basically bypasses the Murphy. As soon as you let off the key that current stops and the Murphy takes over provided that the oil pressure and temperature are good. YEP... that will work.. The one i was familiar with had a BUTTON you hold down while you crank and start... Then let up on the button after you see oil pressure on the gauge..
	Like them all, but love the "B"s.

IBWD MIke Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 08 Apr 2012 Location: Newton Ia. Points: 3530	Post Options Post Reply Quote IBWD MIke Report Post Thanks(0) Quote Reply Posted: 15 Jun 2024 at 7:03am
	I don't know why but a high % of Red tractors, (and engines) with distributors have those resistors like Steve mentions. I eliminate them! Make sure you've got a 3 ohm coil with a 12 volt system. I really don't get why they are so popular?