Starliner Posted September 18, 2020 Author Share Posted September 18, 2020 Note that you will see pulsing voltage on the sender wire. The ICVR acts like a very fast flasher module. Also you will see the zigzag line between the 'N' and ICVR in the diagrams above. That is a resistor used to limit current applied to the instruments. Out of the blue the rear tank started reading again. Front tank still no show on the guage. Actually not fully no go, it comes right up to E when I turn the key on. I guess I'll run the tank empty and start over. I'm leaning toward a bad plug at the sending unit. I will update. Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 18, 2020 Share Posted September 18, 2020 Out of the blue the rear tank started reading again. Front tank still no show on the guage. Actually not fully no go, it comes right up to E when I turn the key on. I guess I'll run the tank empty and start over. I'm leaning toward a bad plug at the sending unit. I will update. Joe - You can test by grounding the wire that goes to the sending unit. The gauge should go to Full and then some. So if you ground the DB/Y wire at the tank and the gauge pegs you'll know that the wiring to the front sending unit is good. Ditto the Y/LB Hash wire for the rear tank. Don't leave it on forever, but you can ground it for a while and not hurt anything. Link to comment Share on other sites More sharing options...
Starliner Posted September 18, 2020 Author Share Posted September 18, 2020 Joe - You can test by grounding the wire that goes to the sending unit. The gauge should go to Full and then some. So if you ground the DB/Y wire at the tank and the gauge pegs you'll know that the wiring to the front sending unit is good. Ditto the Y/LB Hash wire for the rear tank. Don't leave it on forever, but you can ground it for a while and not hurt anything. Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 18, 2020 Share Posted September 18, 2020 Wow, cool trick knowing it wont kill things. You guys have obviously suffered through this stuff to have suck a knowledge base. Thanks. Some of my "knowledge" has been acquired vicariously as I've been "reading the mail" regarding these trucks on forums for over a decade. There's another test that might actually be easier if you have a test light. You can connect it to ground on one side and to the wire to the sending unit on the other. It should blink if the circuit is good. Link to comment Share on other sites More sharing options...
Machspeed Posted September 18, 2020 Share Posted September 18, 2020 Out of the blue the rear tank started reading again. Front tank still no show on the guage. Actually not fully no go, it comes right up to E when I turn the key on. I guess I'll run the tank empty and start over. I'm leaning toward a bad plug at the sending unit. I will update. Joe, are your tanks out? I'm almost wondering if it would be easier to pull the bed than to drop the tanks should I have to go there. Link to comment Share on other sites More sharing options...
Starliner Posted September 18, 2020 Author Share Posted September 18, 2020 Joe, are your tanks out? I'm almost wondering if it would be easier to pull the bed than to drop the tanks should I have to go there. Sure, blinking because of the pulsing voltage, I will look. Because there is no rust, i can drop both tanks in 20 minutes. People love these trucks. I often hear "what year is that" pretty much every day. Now that I have it running right I love driving it. Link to comment Share on other sites More sharing options...
Starliner Posted September 18, 2020 Author Share Posted September 18, 2020 Sure, blinking because of the pulsing voltage, I will look. Because there is no rust, i can drop both tanks in 20 minutes. People love these trucks. I often hear "what year is that" pretty much every day. Now that I have it running right I love driving it. Gremlins. Now both guages are working. I'm thinking intermittent ground issue, (maybe wiggle the dash plug), but since it ain't broke now I am going to leave it be. Link to comment Share on other sites More sharing options...
Machspeed Posted September 19, 2020 Share Posted September 19, 2020 Gremlins. Now both guages are working. I'm thinking intermittent ground issue, (maybe wiggle the dash plug), but since it ain't broke now I am going to leave it be. Well good for you! Bummer for me though, as I was hoping I could find some common issue for my fix, which I think may be ground related. Link to comment Share on other sites More sharing options...
FuzzFace2 Posted September 19, 2020 Share Posted September 19, 2020 Well good for you! Bummer for me though, as I was hoping I could find some common issue for my fix, which I think may be ground related. IIRC the ground wire for the rear of the 82 or 83> trucks runs to the fire wall behind the radio as a bunch go there. I am pretty sure the 80/81 trucks don't have this ground and things ground to the frame or somewhere else on the body. I know my 81 does not have this "behind the radio" ground but has a bunch on the firewall in the engine bay side. Also how is the ground from the battery to motor / frame / body? If the frame or body ground is in question that could be the issue. Dave ---- Link to comment Share on other sites More sharing options...
Starliner Posted September 20, 2020 Author Share Posted September 20, 2020 IIRC the ground wire for the rear of the 82 or 83> trucks runs to the fire wall behind the radio as a bunch go there. I am pretty sure the 80/81 trucks don't have this ground and things ground to the frame or somewhere else on the body. I know my 81 does not have this "behind the radio" ground but has a bunch on the firewall in the engine bay side. Also how is the ground from the battery to motor / frame / body? If the frame or body ground is in question that could be the issue. Dave ---- Definitely clean all grounds you can on an old truck. I'm not sure why my guages woke up but I CAN tell you that I do not baby the girl and maybe hitting a good bump helped. Link to comment Share on other sites More sharing options...
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