Gary Lewis Posted June 12, 2021 Share Posted June 12, 2021 So I think there is a wiring harness issue. The wire coming out of 58 on the eec is green and white not the color on the diagram. When I follow this wire it splices and one leg goes up to a 4 plug connector that goes to injectors, the other leg goes out another branch of harness rona diode. Anywhere I test the green and white cord from end near ecc to end near diode I get a .6 reading on 200 ohm setting. If I test a injector plug wire to the other end where the c160 plug is I get a 30 on one prong in the plug and a .6 on another. Not sure if this is useful information or not. The .6 is basically a dead short to ground. The 30 is probably the resistance of the coil in the injector. Well, looking at the EVTM there is a Dark Green/White wire on pin 30 of the EEC and it goes to a diode, as shown below in the lower left. That is called the Neutral Drive Switch. Does it look like someone has hacked your wiring and connected 30 to 58? If so, I would disconnect the hack and just have the wire from the injectors go to 58 and nowhere else. Link to comment Share on other sites More sharing options...
axe2011 Posted June 12, 2021 Author Share Posted June 12, 2021 The .6 is basically a dead short to ground. The 30 is probably the resistance of the coil in the injector. Well, looking at the EVTM there is a Dark Green/White wire on pin 30 of the EEC and it goes to a diode, as shown below in the lower left. That is called the Neutral Drive Switch. Does it look like someone has hacked your wiring and connected 30 to 58? If so, I would disconnect the hack and just have the wire from the injectors go to 58 and nowhere else. I’m not sure the wiring harness is original the wire in the 58 pin position is actually green and white instead of the color in tan orange it’s supposed to be….near the oil cap there is a spot where once I unwrapped the wire I found every wire was connected…this just got much more complicated! So does .6 mean the wire is grounded out? Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 12, 2021 Share Posted June 12, 2021 I’m not sure the wiring harness is original the wire in the 58 pin position is actually green and white instead of the color in tan orange it’s supposed to be….near the oil cap there is a spot where once I unwrapped the wire I found every wire was connected…this just got much more complicated! So does .6 mean the wire is grounded out? Yes, .6 ohm is almost a dead short. Zero ohms would be a dead short, but I'll bet if you touch the leads of your DVM together it only comes down to .2 or .1 ohms. In that case you are seeing the resistance of the leads - or a meter that hasn't been zeroed. Your truck may well be like many others - an onion you'll have to peel and cry, peel and cry. But eventually you'll have enough for a mess of onion rings! Seriously, you will need to sort out that wiring. It is ok for the wire to be the wrong color as long as it goes from the right place to the right place(s) and nowhere else. So get the injector wiring sorted and then, once the engine will run, work on the next layer of the onion. Link to comment Share on other sites More sharing options...
85lebaront2 Posted June 12, 2021 Share Posted June 12, 2021 I’m not sure the wiring harness is original the wire in the 58 pin position is actually green and white instead of the color in tan orange it’s supposed to be….near the oil cap there is a spot where once I unwrapped the wire I found every wire was connected…this just got much more complicated! So does .6 mean the wire is grounded out? Here is a 1986 EFI harness I sold to another member. C160 is circled, I believe it has 4 wires in it. Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 12, 2021 Share Posted June 12, 2021 Here is a 1986 EFI harness I sold to another member. C160 is circled, I believe it has 4 wires in it. Thanks, Bill. The EVTM, which we got from some nice old guy, only specifies three wires in it but says it has four pins. If there is a fourth wire I'd be curious what it is - but I guess you no longer have the harness. Link to comment Share on other sites More sharing options...
axe2011 Posted June 12, 2021 Author Share Posted June 12, 2021 Thanks, Bill. The EVTM, which we got from some nice old guy, only specifies three wires in it but says it has four pins. If there is a fourth wire I'd be curious what it is - but I guess you no longer have the harness. Yeah this wiring is painful! The connector pictured is the same that is in my truck and has 4 wires. Not sure what it is for but I will start nugging away at it. Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 12, 2021 Share Posted June 12, 2021 Yeah this wiring is painful! The connector pictured is the same that is in my truck and has 4 wires. Not sure what it is for but I will start nugging away at it. Please let me know what the wire colors are. I'm curious what else is in that connector. Link to comment Share on other sites More sharing options...
axe2011 Posted June 12, 2021 Author Share Posted June 12, 2021 Please let me know what the wire colors are. I'm curious what else is in that connector. This is what the plug looks like. Tan green red and black wires Link to comment Share on other sites More sharing options...
85lebaront2 Posted June 12, 2021 Share Posted June 12, 2021 Thanks, Bill. The EVTM, which we got from some nice old guy, only specifies three wires in it but says it has four pins. If there is a fourth wire I'd be curious what it is - but I guess you no longer have the harness. It will have 4, they will be 12V power to injectors, bank 1, bank2, O2 sensor. In the picture, the injector harness is the one shorter portion beyond C160. I would start there, on the injector side and using a multimeter, first check that # 5 & 8 injectors are connected to red and one of the other wires (should be tan with an orange hash). Then repeat for # 6 & 7 those should be red power and tan with a red hash. Colors will fade and change after 35 years. Once you have verified those then there may be a wiring issue or a bad EEC. The 4th wire in C160 is the O2 sensor and is supposed to be dark green with a purple hash. One common problem with these first gen EFI trucks, the ground for the entire system is a two 1/4" pin connector that is pigtailed to the battery negative cable clamp. It is very prone to corrosion which will really mess up the functions. Link to comment Share on other sites More sharing options...
axe2011 Posted June 12, 2021 Author Share Posted June 12, 2021 It will have 4, they will be 12V power to injectors, bank 1, bank2, O2 sensor. In the picture, the injector harness is the one shorter portion beyond C160. I would start there, on the injector side and using a multimeter, first check that # 5 & 8 injectors are connected to red and one of the other wires (should be tan with an orange hash). Then repeat for # 6 & 7 those should be red power and tan with a red hash. Colors will fade and change after 35 years. Once you have verified those then there may be a wiring issue or a bad EEC. The 4th wire in C160 is the O2 sensor and is supposed to be dark green with a purple hash. One common problem with these first gen EFI trucks, the ground for the entire system is a two 1/4" pin connector that is pigtailed to the battery negative cable clamp. It is very prone to corrosion which will really mess up the functions. Ok I’ve been busy today. I took out the injector harness side of the c160 and took it inside. I then unwrapped it and traced all the wires and labeled them using the diagram to get a handle on colors. When I touch the tan and orange (pin58 wire on ecc) wire prong inside of c160 to the blue wire that goes to injector 5 I get a reading of .8 T/o to injector 8 tan and blue is also .8 T/o to injector 4 is .8 T/0 to injector 1 is .8 When I test all the wires spliced to the pin 69 wires injectors 6,7 and 2,3 I also get .8. I have the meter set at 200 ohm am I doing it wrong? I peeled back all the wires to inspect them and didn’t see any obvious damage other than the O2 sensor which looks not good. Link to comment Share on other sites More sharing options...
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