89jeep-comanche Posted November 29, 2018 Share Posted November 29, 2018 I turned on the key and my fuel gauge needle went right to empty and even past it. Now just stays there. Any ideas? Link to comment Share on other sites More sharing options...
Ωhm Posted November 30, 2018 Share Posted November 30, 2018 Need to determine if fuel sending unit is functioning properly. Disconnect connector either at fuel pump (C139) or the flat six pin connector (C157) near parking brake. Using this specification, 0Ω's=Empty and 88Ω's=Full. Connect DVOM to C157_C (fuel pump side) and ground or connect DVOM to C139_A and C139_B (fuel pump side). Measure resistance. Example for good fuel sender would be, if you think you have a half tank of fuel, measurement should be around (non linear) 44Ω's. Link to comment Share on other sites More sharing options...
89jeep-comanche Posted November 30, 2018 Author Share Posted November 30, 2018 Alright I’ll start there and see what I get. Link to comment Share on other sites More sharing options...
89jeep-comanche Posted November 30, 2018 Author Share Posted November 30, 2018 I moved the needle y accident when I was wiping dust out. Does that hurt anything internally on the gauge? Or effect readings? Link to comment Share on other sites More sharing options...
89jeep-comanche Posted December 2, 2018 Author Share Posted December 2, 2018 My readings were good. In range of what was in the tank Link to comment Share on other sites More sharing options...
Ωhm Posted December 2, 2018 Share Posted December 2, 2018 Is vehicle equipped with Low Fuel Warning Module (LFWM)? Link to comment Share on other sites More sharing options...
89jeep-comanche Posted December 3, 2018 Author Share Posted December 3, 2018 you’re talking about the one inside the quage cluster? Link to comment Share on other sites More sharing options...
Ωhm Posted December 3, 2018 Share Posted December 3, 2018 Yeah, that will determine which cluster pins will need to be tested for power and ground, but since fuel gauge is your only problem and all other cluster items work, suspect printed circuit or faulty fuel gauge or possible faulty Low Fuel Warning Module, if equipped. Link to comment Share on other sites More sharing options...
89jeep-comanche Posted December 3, 2018 Author Share Posted December 3, 2018 Alright. I’m not 100% sure it’s equipped. I didn’t take notice of it but it has the light. So I figure it is Link to comment Share on other sites More sharing options...
Ωhm Posted December 3, 2018 Share Posted December 3, 2018 Fuel gauge has three legs. Power, ground, and the fuel sending unit. Sending unit leg seem good from your point of measurement to sending unit. Check power (key on) and ground (key off) at disconnected Instrument Cluster C203. Re--measure fuel sending unit. C203_18 (B+). C203_10 (GND). C203_17 (fuel sending unit Ω). Using the following link for reference: http://www.bteventures.com//mj1988electricalmanual.pdf Page 29, Page 78, Page 95 Link to comment Share on other sites More sharing options...
89jeep-comanche Posted December 3, 2018 Author Share Posted December 3, 2018 I’ll get to it Link to comment Share on other sites More sharing options...
89jeep-comanche Posted December 3, 2018 Author Share Posted December 3, 2018 #18 has power with key on #10 has 0.1 ohms with key off #17 has same ohms had when I tested C139 Link to comment Share on other sites More sharing options...
Ωhm Posted December 3, 2018 Share Posted December 3, 2018 13 minutes ago, 89jeep-comanche said: #18 has power with key on #10 has 0.1 ohms with key off #17 has same ohms had when I tested C139 Wiring tested good. On 11/30/2018 at 7:26 AM, 89jeep-comanche said: I moved the needle y accident when I was wiping dust out. Does that hurt anything internally on the gauge? Or effect readings? Don't know of any test for the LFWM. Seems to be either fuel gauge or printed circuit. Look for open circuits on the printed circuit. Maybe it was a bad day to dust. Link to comment Share on other sites More sharing options...
89jeep-comanche Posted December 4, 2018 Author Share Posted December 4, 2018 Haha yeah you’re probably right. Any places selling gauges you know of? Link to comment Share on other sites More sharing options...
Ωhm Posted December 4, 2018 Share Posted December 4, 2018 Try posting in the sites Classified section / Wanted. Link to comment Share on other sites More sharing options...
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