bcbill Posted November 27, 2016 Share Posted November 27, 2016 Just picked up a 89 4.0 L, 5 speed LB and the fuel gauge is pegged at full, tracked down replacement sending units at Autozone and on Amazon, trouble is the Delphi part number are different, Autozone says the part I need is HP10148 while different retailers on amazon say the part is HP101147. Any help with this would be appreciated. Thanks Link to comment Share on other sites More sharing options...
87MJTIM Posted November 27, 2016 Share Posted November 27, 2016 You probably have an XJ sending unit. It is not compatible with the MJ tank. The units face opposite directions. Does the gauge drop as you drive? The wiring may be crossed. I remember reading that Renix and HO jeeps are wired opposite. There is a thread on CC on rebuilding the pump/sending unit. Link to comment Share on other sites More sharing options...
bcbill Posted November 27, 2016 Author Share Posted November 27, 2016 Thanks for quick reply, the gauge reads full constantly, even with key off it remains pegged at full. From research I have done on here and other places what I am finding is that the fuel sending unit is not available and was surprised when i searched on goggle and found it at Autozone and on Amazon but are they just selling the XJ unit thinking it will fit the MJ.... Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 27, 2016 Share Posted November 27, 2016 To test the fuel gauge, unplug the connector at the tank. That leaves an open circuit to the sender. The gauge should peg to the right. Then take the chassis side of the connector and jumper the smaller colored wire to the black. That closes the fuel gauge circuit with zero resistance. The needle should swing to empty. If the needle doesn't respond when you do this, then either the gauge is bad or there's a wiring problem. ^^ Try this test to see if the gauge needle moves at all, but since you say the gauge stays pegged with and without the key on, I'd lean toward a stuck meter movement on the fuel gauge itself. Link to comment Share on other sites More sharing options...
bcbill Posted November 27, 2016 Author Share Posted November 27, 2016 Thanks for tip, will look at replacing fuel gauge first, that will probably be the easiest place to start... Link to comment Share on other sites More sharing options...
DirtyComanche Posted November 27, 2016 Share Posted November 27, 2016 I'd suspect a broken wire over a bad gauge. IIRC, the Renix sweep is 0-88ohm with 88ohms being full, if there is a broken wire it sees 'infinite' resistance and just pegs the gauge. The gauges in the Renix rigs are actually pretty reliable. I'd suggest heading over to Cruiser's site and getting a copy of the FSM, and doing some prodding with a multimeter, rather than just throwing parts at it. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 27, 2016 Share Posted November 27, 2016 He says the gauge is pegged all the time even with the ignition key off. Link to comment Share on other sites More sharing options...
DirtyComanche Posted November 27, 2016 Share Posted November 27, 2016 He says the gauge is pegged all the time even with the ignition key off. And? It stays where it was when shut off on a Renix. Link to comment Share on other sites More sharing options...
DirtyComanche Posted November 27, 2016 Share Posted November 27, 2016 Also, you can drive the gauge without a multimeter, just by grounding the wire for it, or removing it from being connected. It will confirm that it works. The issues is without knowing what wire it is, or what pin it is in a connector, it's not a lot of help. If you look at the printed 'circuit board' on the back of the cluster you can figure out which one it is. But like I said, grab a copy of the FSM and look at the diagrams, I'd just post them for you but Photobucket is completely useless now and will not allow me to upload from my phone. Edit, I wasn't thinking and wrote a pretty bad bit of advice in the first version of this post. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 27, 2016 Share Posted November 27, 2016 I usually touch a 9V test battery across it to test meter movement. Link to comment Share on other sites More sharing options...
Knucklehead97 Posted November 28, 2016 Share Posted November 28, 2016 My gauge on my stickshift MJ was pegged over full. It was because a wire was burnt off the sender inside the tank. I have the old sender somewhere... I'll look for it and snap a pic when I get the chance. Link to comment Share on other sites More sharing options...
bcbill Posted November 30, 2016 Author Share Posted November 30, 2016 Hey guys, thanks for the input, am in process of pulling gauge cluster, hope to replace the fuel gauge or whole cluster with one from wreckers, another question tho, the po replaced the original trans and transfer case, the transfer case is from a 91 and has the electronic speedo plug while the cable from the speedometer is the mechanical gear driven, been told just need to replace the electronic plug on the transfer case with the older mechanical plug, seems to be to easy a fix to me, anyone with experience with this.... Link to comment Share on other sites More sharing options...
bcbill Posted November 30, 2016 Author Share Posted November 30, 2016 Getting back to the original post.... is there an aftermarket fuel sending unit for the 89 Lb Comanche or are suppliers just assuming that the XJ units will fit the MJ and selling them as such.... Link to comment Share on other sites More sharing options...
mikekaz1 Posted November 30, 2016 Share Posted November 30, 2016 you should be able to swap the electronic gear and the mechanical gear no problem in the tcase. as for fuel sending units yes, its vendor mis representation of thinking MJs are XJs. Link to comment Share on other sites More sharing options...
bcbill Posted November 30, 2016 Author Share Posted November 30, 2016 Thanks mike, there are vendors on Ebay, Amazon and Autozone claiming they have sending units for the MJ but also claim the same unit fits the XJ, guess to replace sending unit it is by having it rebuilt or finding a used one. Link to comment Share on other sites More sharing options...
87MJTIM Posted November 30, 2016 Share Posted November 30, 2016 If I recall, someone on CC offered to rebuild the pump/sending units. I don't know if they're still a member on CC or if they still offer the service. Link to comment Share on other sites More sharing options...
mikekaz1 Posted November 30, 2016 Share Posted November 30, 2016 theres a place in upstate NY that repairs sending units and/or will build a brand new one for you. doesn't charge too badly too. repairs anywhere from $70-300 on average. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 30, 2016 Share Posted November 30, 2016 If I recall, someone on CC offered to rebuild the pump/sending units. I don't know if they're still a member on CC or if they still offer the service. That would be Akula69b (Jake). http://comancheclub.com/topic/33662-refurbishing-the-fuel-sender/?hl=jake&do=findComment&comment=338625 Link to comment Share on other sites More sharing options...
Newton Posted November 30, 2016 Share Posted November 30, 2016 Fuel gauge pegged full = bad ground Pegged empty = bad power Link to comment Share on other sites More sharing options...
bcbill Posted December 1, 2016 Author Share Posted December 1, 2016 Ok lets assume bad ground, would that be at the sender or at the gauge.. Link to comment Share on other sites More sharing options...
bcbill Posted December 1, 2016 Author Share Posted December 1, 2016 I am starting to enjoy this forum, shouda got a Comanche long time ago :) :) :) Link to comment Share on other sites More sharing options...
Newton Posted December 1, 2016 Share Posted December 1, 2016 u can start by refreshing ground behind driver side tail light u can also pull fuel pump from tank and use a multi meter to check for ohms reading by moving the arm on the sending unit to rule out a bad sender and if that checks out ok then you can check sender wire going to gauge cluster and if thats not it then maybe you have a bad cluster which i doubt but u never know Link to comment Share on other sites More sharing options...
bcbill Posted December 2, 2016 Author Share Posted December 2, 2016 Replaced fuel gauge, looked at and cleaned up the rear light ground, gauge still reads at full, with key on and key off so now it is time to look at the sending unit itself didnt really want to mess with the sending unit as they are hard to find but will pull it out and check it, did find a link to the rebuld web site.... also the mechanical speedo unit slides right in to replace the electronic unit..sweet.. Link to comment Share on other sites More sharing options...
Eagle Posted December 3, 2016 Share Posted December 3, 2016 Replaced fuel gauge, looked at and cleaned up the rear light ground, gauge still reads at full, with key on and key off so now it is time to look at the sending unit itself No, now it is time to look at the wiring between the gauge and the sending unit. Do the test suggested -- find the plug where the fuel pump/sender harness pigtail connects to the chassis harness. Unplug it. Turn on ignition. See where gauge reads. (Should be Full) Then identify the wire in the chassis harness side for the sender input. Connect to ground. See where gauge reads. (Should read Empty.) Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 3, 2016 Share Posted December 3, 2016 ^^ Do-the-gauge-test-as-in-post-#4. Also, since it sounds like this MJ is new to you, inspect the flex circuit foil on the back of the cluster. If the copper trace going to the fuel gauge input terminal is torn or cracked open, the gauge will stay pegged no matter what you do. And of course, make sure the screws securing the foil to the gauge mounting posts are tight and making a good electrical connection. Link to comment Share on other sites More sharing options...
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