Rusty_S85 Posted June 12, 2021 Share Posted June 12, 2021 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. How he can check for a short is to unplug the harness completely for that circuit then check the circuit to ground and then check the circuit to positive with it completely disconnected and isolated it should show up NA or OL. If there is any reading then it is confirmed shorted to either ground or voltage. Its a fairly basic test us technicans do at work to isolate circuits and verify a short to ground or power. Lets say the wire is from connector 1 to connector 3. You unplug connector 1 and unplug connector 3. You then probe the wire at connector one and at connector three check resistance. Then remove one of the probes and touch it to chassis ground or negative battery cable (battery should be disconnected for any resistance tests) if you get a reading with the wire isolated it is shorted to ground. Do the same thing to the positive cable, if any reading then its shorted to power. Once you confirm this you can unwrap that leg of wire and find the short. It is quite possible the reading he is getting is "normal" in a sense and may not be an actual short. Its also quite possible the short isnt in the wire itself but is in the ECM itself internally which you wouldnt know unless you unplug the circuit to isolate it from everything else. Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 12, 2021 Share Posted June 12, 2021 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. How he can check for a short is to unplug the harness completely for that circuit then check the circuit to ground and then check the circuit to positive with it completely disconnected and isolated it should show up NA or OL. If there is any reading then it is confirmed shorted to either ground or voltage. Its a fairly basic test us technicans do at work to isolate circuits and verify a short to ground or power. Lets say the wire is from connector 1 to connector 3. You unplug connector 1 and unplug connector 3. You then probe the wire at connector one and at connector three check resistance. Then remove one of the probes and touch it to chassis ground or negative battery cable (battery should be disconnected for any resistance tests) if you get a reading with the wire isolated it is shorted to ground. Do the same thing to the positive cable, if any reading then its shorted to power. Once you confirm this you can unwrap that leg of wire and find the short. It is quite possible the reading he is getting is "normal" in a sense and may not be an actual short. Its also quite possible the short isnt in the wire itself but is in the ECM itself internally which you wouldnt know unless you unplug the circuit to isolate it from everything else. Axe - Rusty is right, your readings look normal, but you really aren't testing correctly. Try the way he suggested - test to ground, which seems to be the problem you were having. Having said that, I don't think your problem is in that harness. I think it is in the one going to the computer. And you don't want to be testing with the computer plugged into the harness. So I suggest you unplug the computer and then test the wire that is supposed to go to pin 58. You should see nothing when testing to ground or to power. I think you may find that it shows low resistance to ground. Rusty - I think he's already tested with another computer and gotten the same results, so it must not be the computer. Link to comment Share on other sites More sharing options...
axe2011 Posted June 13, 2021 Author Share Posted June 13, 2021 Axe - Rusty is right, your readings look normal, but you really aren't testing correctly. Try the way he suggested - test to ground, which seems to be the problem you were having. Having said that, I don't think your problem is in that harness. I think it is in the one going to the computer. And you don't want to be testing with the computer plugged into the harness. So I suggest you unplug the computer and then test the wire that is supposed to go to pin 58. You should see nothing when testing to ground or to power. I think you may find that it shows low resistance to ground. Rusty - I think he's already tested with another computer and gotten the same results, so it must not be the computer. I think I made some progress tonight. We took a test light and found that pin 58 wire had a diode spliced into it that goes to the drivers side of the truck. When I unplugged the connector on the other side of the diode it stopped grounding the injectors. I then looked at pin 30 and found that it didn’t go to a diode like it was supposed in the diagram to but rather straight to a unused plug on the passengers side of the truck. We cut the grounding wire off the pin 58 wire and we’re going to test it out….but of course in the process of pulling in and out injectors I messed up an oring….so gotta pick up some of those now. Fingers crossed I have the first layer figured out and I can rewrap some wires. Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 13, 2021 Share Posted June 13, 2021 I think I made some progress tonight. We took a test light and found that pin 58 wire had a diode spliced into it that goes to the drivers side of the truck. When I unplugged the connector on the other side of the diode it stopped grounding the injectors. I then looked at pin 30 and found that it didn’t go to a diode like it was supposed in the diagram to but rather straight to a unused plug on the passengers side of the truck. We cut the grounding wire off the pin 58 wire and we’re going to test it out….but of course in the process of pulling in and out injectors I messed up an oring….so gotta pick up some of those now. Fingers crossed I have the first layer figured out and I can rewrap some wires. Yippee!!! That is great progress! I'll bet the thing will run once you get the o-ring replaced. If so, you have one layer peeled. Link to comment Share on other sites More sharing options...
axe2011 Posted June 13, 2021 Author Share Posted June 13, 2021 Yippee!!! That is great progress! I'll bet the thing will run once you get the o-ring replaced. If so, you have one layer peeled. I got some o-rings and put the rail back on. The truck started and ran!! In the process I may have killed off a sensor that sticks into the side near injector 6 and 7. I have to figure out what that is and get a new one, but I was able to start it. I let it run for a few minutes and then went up and down the driveway. I didn't have temp reading so I turned it off because I didn't want to have it overheat and me not know. I appreciate everyone's help with this first issue! I am sure I will find more as I try to figure out what happened to the old girls wiring. Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 13, 2021 Share Posted June 13, 2021 I got some o-rings and put the rail back on. The truck started and ran!! In the process I may have killed off a sensor that sticks into the side near injector 6 and 7. I have to figure out what that is and get a new one, but I was able to start it. I let it run for a few minutes and then went up and down the driveway. I didn't have temp reading so I turned it off because I didn't want to have it overheat and me not know. I appreciate everyone's help with this first issue! I am sure I will find more as I try to figure out what happened to the old girls wiring. Excellent!!! You really solved a tough problem. Well done! On the sensor, there may be a number on it. Let me know what that is and I should be able to figure it out. Or give me the color of the wires if there is no number. Link to comment Share on other sites More sharing options...
Rusty_S85 Posted June 13, 2021 Share Posted June 13, 2021 Axe - Rusty is right, your readings look normal, but you really aren't testing correctly. Try the way he suggested - test to ground, which seems to be the problem you were having. Having said that, I don't think your problem is in that harness. I think it is in the one going to the computer. And you don't want to be testing with the computer plugged into the harness. So I suggest you unplug the computer and then test the wire that is supposed to go to pin 58. You should see nothing when testing to ground or to power. I think you may find that it shows low resistance to ground. Rusty - I think he's already tested with another computer and gotten the same results, so it must not be the computer. When it comes to electrical systems you kind of have to view the component as possibly bad even if it isnt. Ive seen brand new electrical parts fresh out of the box be bad so I try not to write a new part off as good. I went through that with an alternator on my '63, it took 4 alternators to get one that actually charged, the guy at the parts house told me that he wont give me another one cause if this one doesnt fix it then its something wrong with my car and not the alternators. I told him the old one was charging it had a bad diode trio resulting in a short to positive and a dead battery over night. The 4th alternator fixed it but those previous 3 so called new/remanufactured alternators were defective out of the box. Link to comment Share on other sites More sharing options...
axe2011 Posted June 13, 2021 Author Share Posted June 13, 2021 Excellent!!! You really solved a tough problem. Well done! On the sensor, there may be a number on it. Let me know what that is and I should be able to figure it out. Or give me the color of the wires if there is no number. Left town for a couple days I’ll try to get on number on it Thursday or Friday depending when I get back from my work trip. Again thanks so much for your help! Link to comment Share on other sites More sharing options...
85lebaront2 Posted June 14, 2021 Share Posted June 14, 2021 Excellent!!! You really solved a tough problem. Well done! On the sensor, there may be a number on it. Let me know what that is and I should be able to figure it out. Or give me the color of the wires if there is no number. Gary, that should be the knock sensor, 1985/86 it is driver's side center of the lower intake. So it is between 6 and 7. Link to comment Share on other sites More sharing options...
axe2011 Posted June 14, 2021 Author Share Posted June 14, 2021 Gary, that should be the knock sensor, 1985/86 it is driver's side center of the lower intake. So it is between 6 and 7. I’ll have to check it out. When I was kneeling on the front tracing wires I slipped and broke it off. I noticed that they deleted the coolant lines that go through the throttle body. The top one is fine and I see the hose that is clamped that I can hook back up, but the bottom hose port has been smushed and soldered shut. It looks like it is separate of the throttle body and could be threaded out and replaced possibly. I live in Iowa so it does get cold here. Is it worth fixing? Anyone know what this part is called and where I could get one? Link to comment Share on other sites More sharing options...
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