IHC wiring
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=201799
Printed Date: 26 Jun 2024 at 12:46pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: IHC wiring
Posted By: Acguywill
Subject: IHC wiring
Date 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. |
Replies:
Posted By: steve(ill)
Date Posted: 14 Jun 2024 at 8:04pm
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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..  ------------- Like them all, but love the "B"s. |
Posted By: steve(ill)
Date 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. |
Posted By: Acguywill
Date 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. |
Posted By: steve(ill)
Date Posted: 14 Jun 2024 at 10:54pm
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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. |
Posted By: steve(ill)
Date Posted: 14 Jun 2024 at 10:56pm
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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. |
Posted By: IBWD MIke
Date Posted: 15 Jun 2024 at 7:03am
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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? |