DaffodilRex Posted January 16, 2021 Share Posted January 16, 2021 So I took my comanche to get a diagnostic when I first got it. My gas gauge doesn't work and the shop said I needed a new fuel pump sending unit assembly. (Among other things) I did everything else they recommended on my own but I recently had the oil leak fixed. I wasn't comfortable doing it, so I sent it in, and had them do the fuel pump sending unit assembly while it was there and in the air. That didn't fix the gauge. It isn't just stuck, and it isn't even working backwards like I was warned about on here. So they said I should start checking wires etc. Or get myself a new cluster. But my gear tree also doesn't work. And I'm wondering if it could be connected? Gear indicator is always on drive regardless of what gear I'm in, and the gas gauge stays where ever I put it. I'm not sure if this is the right spot to post this, or if there's another post like this, if there is I'm sorry. Link to comment Share on other sites More sharing options...
eaglescout526 Posted January 16, 2021 Share Posted January 16, 2021 This is the right spot. Do you have the idiot light cluster or a 3/4 cluster? It is recommended to do the ground fixes if they haven’t been performed. As for the gauge itself you can pull he cluster out and unscrew the gauge from the cluster and take a look at the wire windings on the back to see if there’s anything broken. I had a gas gauge do that to me. As for the PRNDL, there’s a clip that comes out of the bottom of the cluster that clips to something on the column that controls the indicator. Link to comment Share on other sites More sharing options...
DaffodilRex Posted January 16, 2021 Author Share Posted January 16, 2021 36 minutes ago, eaglescout526 said: This is the right spot. Do you have the idiot light cluster or a 3/4 cluster? It is recommended to do the ground fixes if they haven’t been performed. As for the gauge itself you can pull he cluster out and unscrew the gauge from the cluster and take a look at the wire windings on the back to see if there’s anything broken. I had a gas gauge do that to me. As for the PRNDL, there’s a clip that comes out of the bottom of the cluster that clips to something on the column that controls the indicator. Thank you! The grounds have been preformed. I've got some time today so I'll start getting it apart. Attached some pictures of my cluster. Link to comment Share on other sites More sharing options...
Pete M Posted January 16, 2021 Share Posted January 16, 2021 don't pull the cluster out very far until you get the speedo clip unhooked Link to comment Share on other sites More sharing options...
eaglescout526 Posted January 16, 2021 Share Posted January 16, 2021 What Pete said and I would check out the shape of that indicator, looks like the return spring for it could’ve broke. And that’s the idiot light cluster. Link to comment Share on other sites More sharing options...
Pete M Posted January 16, 2021 Share Posted January 16, 2021 while we're on the subject, a full gauge cluster is an easy swap. (but chances are slim finding one with the built-in gear indicator so check the link in my sig for a writeup on modding one in) Link to comment Share on other sites More sharing options...
rylee144 Posted January 16, 2021 Share Posted January 16, 2021 Mine just needed a needed a new fuse in the fuse block under the dash. Link to comment Share on other sites More sharing options...
DaffodilRex Posted January 16, 2021 Author Share Posted January 16, 2021 So I don't know if this means anything but it stays where you put it while the truck is off. But once you crank it, it always returns to empty? Thanks for the help you guys! Link to comment Share on other sites More sharing options...
eaglescout526 Posted January 16, 2021 Share Posted January 16, 2021 Where does gauge point to when the engine is running/driving? Link to comment Share on other sites More sharing options...
87MJTIM Posted January 16, 2021 Share Posted January 16, 2021 There is a write up on fixing the PRNDL in the master search section. The picture links are gone, but the text is still there For fixing the gas gauge, you should test the wiring. Use a DVM. Make sure you have a good ground at the rear, driver's side light. See Cruiser's Tips. Download the 88 electrical wiring diagram to trace the wires. Link to comment Share on other sites More sharing options...
Minuit Posted January 16, 2021 Share Posted January 16, 2021 Not to go off on too much of a soapbox rant, but this is a hard lesson that everyone has to learn at some point. Shops, as a general rule, don't know how to (or don't care to) diagnose a damn thing. Electrical, mechanical, whatever. About the best you can expect is to play the numbers with your money and hope the part they replaced fixed it. There will be exceptions, but they are rare. To that point - correct fuel pump sending unit assemblies are not available new through most aftermarket channels for these trucks. They are made by one small company, and as far as I know most aftermarket places insist on selling you the same one that fits the Cherokee, which is wrong in a number of ways. In fact, if they did replace it (and I have my doubts that they did) you're probably worse off as a result of that. Basic function of the fuel gauge can be tested without doing anything but unplugging the connector at the fuel tank. Got some electrical resistors or willing to buy some? From there, the "location" of the problem on the electrical schematic can be found. The gear indicator is basically made up of a string that hooks to the steering column that is connected at the other end to the pointer which should be spring loaded. You may be able to figure out the problem by removing the cluster, or the indicator might just be broken. Link to comment Share on other sites More sharing options...
schardein Posted January 17, 2021 Share Posted January 17, 2021 The shift indicator is pretty low tech. The red indicator is spring loaded to hold it at park (or close to it). A thin cable runs out the bottom of the instrument cluster. There is a clip on the end of the cable that attaches to the lower edge of the steering column. When you move the shifter to engage a gear, it pulls the cable, which pulls the indicator. Adjust the indicator be adjusting where the clip is on the column. Hopefully these pics help. Link to comment Share on other sites More sharing options...
DaffodilRex Posted January 17, 2021 Author Share Posted January 17, 2021 On 1/16/2021 at 11:20 AM, eaglescout526 said: Where does gauge point to when the engine is running/driving? Empty Link to comment Share on other sites More sharing options...
eaglescout526 Posted January 17, 2021 Share Posted January 17, 2021 Ok I see what you were trying to do. The gauge will always return to empty if it’s not getting a signal from the sending unit. Have you checked the fuse that’s for the cluster? Verified the gauge is getting power? Link to comment Share on other sites More sharing options...
DaffodilRex Posted January 17, 2021 Author Share Posted January 17, 2021 25 minutes ago, eaglescout526 said: Ok I see what you were trying to do. The gauge will always return to empty if it’s not getting a signal from the sending unit. Have you checked the fuse that’s for the cluster? Verified the gauge is getting power? I haven't gotten a chance to mess with it much yet. I did the bumper yesterday, and worked all night so I'm catching up on other things today. But I'll check it out some time this week. You're not the only one to tell me that, so hopefully it's as simple as a fuse *fingers crossed* Link to comment Share on other sites More sharing options...
eaglescout526 Posted January 17, 2021 Share Posted January 17, 2021 Yeah, I saw the other post on the fuse but wanted to reiterate that before getting into the fun stuff of figuring out the issue. Link to comment Share on other sites More sharing options...
OldSch88L Posted January 18, 2021 Share Posted January 18, 2021 Hello Miss! First of all, here's the link to the most valuable tool in owning a Jeep Comanche: https://comancheclub.com/applications/core/interface/file/attachment.php?id=14915 I suggest you learn about reading electrical diagrams if you don't already know how, and then get familiar with this document. Otherwise, diagnosing is like poking in the dark. On my part, I'd start half-way; using the diagram, I'd find the terminals for the gas gauge at the cluster connector. No signal= problem before the cluster (wiring, sending unit, fuse), otherwise signal= problem with either cluster, cluster wiring (IIRC, the white/black stripe wire is the power supply for the cluster) or ground. Also note that improper-era sending units will read opposite of one another; for example, a non-renix (90 and up?) cluster in my '88 truck makes the gauge read empty when full. Also a non-renix sending unit with your stock '88 cluster would also do the same thing. And last, don't just check fuses, also check fuse box terminals for corrosion or failure; I solved many problems just with that! Link to comment Share on other sites More sharing options...
eaglescout526 Posted January 18, 2021 Share Posted January 18, 2021 41 minutes ago, OldSch88L said: 90 and up? 91 and 92 are HO years which would make the gauge read backwards in our trucks. 86-90 is Renix. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 20, 2021 Share Posted January 20, 2021 We all know where the sending unit grounds, right? CRUISER'S MOSTLY RENIX TIPS IMPROVING THE FUEL PUMP GROUND JANUARY 3, 2016 CRUISER54 51 COMMENTS The fuel pump and fuel tank sending unit ground at a sheet metal screw up behind the spare tire on an XJ, and behind the driver’s taillamp on an MJ. Not only is a sheet metal screw a lousy way to ground things, this ground path is long and travels through some connectors that are prone to corrosion and moisture. Locate the black wire on the HARNESS side of the fuel pump/sender 3 wire connector. Remove a 6″ length of the split loom covering. Strip back about 1/2″ of insulation from the BLACK wire. Take your new ground wire, preferably at least 14 gauge and 12 to 18 inches long as needed, strip it about 3/4″, and wrap it around the exposed part of the harness plug wire.Solder the connection. Tape it up and reinstall the split loom covering. At the other end of your new ground wire, add a crimp on eyelet. Attach the eyelet under a bolt that goes directly into the chassis. Be sure to clean the attaching point til shiny and apply OxGard to the contact surfaces. Link to comment Share on other sites More sharing options...
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