87Warrior Posted May 19, 2015 Share Posted May 19, 2015 1986 2.5 TBI My truck has developed a stubborn fuel gauge, meaning it stays at full as I drive it. It now has 3/4-1/2 a tank of fuel (verified by pulling the pump assembly) yet the gauge reads "F" full. I started by checking the ground at the tail light and the weather pack type plug to the pump assembly. I checked the ohm output of the sender installed in the truck and it read 105Ω. As I understand the renix era should read 0-88Ω empty to full. The sender seems to have built up some resistance over time, but hey, none of my Jeep's fuel gauges read 100% accurate. I unplugged the pump assembly and the gauge read well past the full mark. I believe this is what should happen. I then pull the pump and sender from the truck and manually manipulate the sender's float arm. The gauge in the truck responds as it should; float bottomed out the gauge indicates empty (low fuel light NOT illuminated), float all the way up the gauge indicates full, etc. I removed the cover on the side of the sending unit and the fins/resistor strip appeared to be in good condition with no obvious sign of damage. The contact path along the fins/resistor strip had a tan appearance. Another antecedent to this whole ordeal. A couple of days ago I left town in the dark after a long day of volunteer work with a recently topped off fuel tank. While rounding a corner my 'low fuel' light flickered on and off a few times while the gauge stayed at full. What am I missing? What could be the root of these issues? I suspect the sending unit may be failing or may need cleaned up. Is it possible to clean any varnish or tarnish from the fin/resistor strip in the sending unit? Link to comment Share on other sites More sharing options...
Eagle Posted May 19, 2015 Share Posted May 19, 2015 If the gauge reads correctly when you manipulate the sender manually, I don't see an electrical problem. It sounds more like the float arm may be binding up or being obstructed when installed in the tank. When you had it out and were testing it manually, did the arm move freely? Link to comment Share on other sites More sharing options...
87Warrior Posted May 19, 2015 Author Share Posted May 19, 2015 I suspected a stuck float as well. However the float arm moved freely with with little to no resistance. I couldn't look into the tank for any random obstruction since it it is still installed, but I can't imagine anything inside the tank would be an issue. Link to comment Share on other sites More sharing options...
Jeep Driver Posted November 4, 2017 Share Posted November 4, 2017 Can someone confirm that the '86 sender is 0-90 ohms? Does anyone have a pic or part number for the pick up screen? https://www.ebay.com/itm/NOS-86-Jeep-Comanche-Fuel-Tank-sending-unit-assy-23-5-gallon-tank-52003652/232057535509?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649 Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted November 4, 2017 Share Posted November 4, 2017 That's the wrong sender for the 2.5 TBI , the eBay sender you have linked to doesn't have a screen , only a filter mounted to the frame rail . Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted November 4, 2017 Share Posted November 4, 2017 But if you're looking for for the correct tbi screen ... https://m.ebay.com/itm/NOS-Lot-of-12-In-Tank-Fuel-Filters-1984-1993-Dodge-Jeep-Eagle-33003592-dp-/142361574216 Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 4, 2017 Share Posted November 4, 2017 I think it's an electrical problem. You can check out the fuel sender potentiometer as the cause for the erratic gauge readings at the three pot slider terminals using an analog ohmmeter. First read the total resistance across the pot (~90 ohms, but not sure on an 86), then across the slider terminal to both pot end terminals while moving the float arm slowly up, then down. The ohmmeter needle should move smoothly and consistently w/o glitches. If all is well, check/clean every terminal connector you can get to between the sender output, through the body harness to the dash gauge. Link to comment Share on other sites More sharing options...
Jeep Driver Posted November 4, 2017 Share Posted November 4, 2017 No, I don't have a problem. I'm about to place my deposit on the custom gauge cluster, the only gauge that does not come with a sender is the fuel gauge. I need to tell them what gauge to use. I'm going with a rail mounted fuel pump for the injected V8, the '86 arrangement is perfect for what I'm going. I just needed to confirm the ohm range, if I'm not mistaken, the 0-90 is GM and Jeeps of the Renix era used GM senders. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 4, 2017 Share Posted November 4, 2017 28 minutes ago, Jeep Driver said: No, I don't have a problem. I'm about to place my deposit on the custom gauge cluster, the only gauge that does not come with a sender is the fuel gauge. I need to tell them what gauge to use. I'm going with a rail mounted fuel pump for the injected V8, the '86 arrangement is perfect for what I'm going. I just needed to confirm the ohm range, if I'm not mistaken, the 0-90 is GM and Jeeps of the Renix era used GM senders. I was responding to the OP. Link to comment Share on other sites More sharing options...
Jeep Driver Posted November 4, 2017 Share Posted November 4, 2017 1 minute ago, HOrnbrod said: I was responding to the OP. You're 2.5 years late. Link to comment Share on other sites More sharing options...
Nick88 Posted February 22, 2018 Share Posted February 22, 2018 Did you ever find the OHM Range? I'm In a similar situation. I just bought a whole set of glow $#!& gauges, the fuel gauge has 9 different settings for adjustment to make sure the gas gauge is accurate. sorry to dig up an old thread.... mines an 88 Link to comment Share on other sites More sharing options...
Green Mesa XJ Posted February 22, 2018 Share Posted February 22, 2018 Don’t have books in front of me however in one of these fuel gauge threads I posted they 84-90 fuel gauge ohms, the reverse 91 up where the AMC empty is Chrysler full. Sent from my iPhone using Tapatalk Pro Link to comment Share on other sites More sharing options...
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