JDziark

I have the same issue. Vacuum advance is not working. When testing with a vacuum pump, it moves only at full vacuum; FSM indicates it should start moving at about 100 mm Hg. Does anyone know if these can be repaired and if so, who does it? Thanks.

OK, I have the same concern as '240zcv'. I have a 72 240z and the vacuum advance canister barely moves. If I physically pull vacuum on it, I can barely get it to move; I don't think there is any way this thing will move at all when the engine is running. If you pull vacuum by sucking on the vacuum hose, how easy should it be to see movement of the vacuum canister arm? Thanks.

Good point on the calibration. I'm thinking of taking out the sending unit, hook it up to the gauge and manually move the float up and down to see the effect on the needle. I did put some gas in the tank and am not sure if it's above the level of the sending unit.

More info. Played around with the gauge. The 'stud' that the points close again is actually threaded. I turned it in about a quarter turn to insure good contact with the other end. Putting a current to the yellow/red wire and checking the voltage at the yellow wire gives a nice variable voltage reading. I ordered some higher wattage bulbs for the dash and will wait for those to come in before hooking everything back up. Great learning experience - thanks to you guys. If anything else comes up, I'll let you know. John

OK, bad contacts it appears to be. When I apply 12V to the feed (yellow/red wire) and measure the voltage of the yellow wire, it's >1V. If I apply a little pressure to the contact, it goes up to 12V. Captain, as you suggested, I'll start with a strip of paper but may eventually go to a thin piece of some kind of slightly abrasive material. I'll keep you guys posted. This whole restoration project has been a case of 3 steps forward, 2 back. Now I have to fix the gauge and then put everything back together again. Do either of you have any tricks up your sleeve to reattach the cable going to the heater control valve? Those are tough screws to get at. When I took that cable off, I just loosened the screw holding the cable to the heater box and pulled the cable through it. I hope I can just feed it back in and retighten the screw that's already in place. John

Steve, thanks. I'll wait for your video. In the mean time, I'll work at removing the gauge. I could just keep the tank full of gas but the thing not working is annoying. John

Captain, great input! Thanks. I probably measured the resistance wrong, the prongs were very hard to contact with the gauge in the dash. I wondered if the regulator switch was like a set of points. Imagine how many times that switch turned on and off over the last almost 50 years! I've gone this far and will continue and take out the gauge. It will be a lot easier to work on. Is that picture (very helpful, thanks) taken from the front of the gauge? If so, how do you get the needles/faceplate off? I'm the original and only owner of this car, it's been a long process to refurbish it and it hurt to take all that stuff out of the dash (again!) but part of the fun is learning a little more about the car as I go along. Wish me luck. John

Captain, a little more data. 1). When I back fed the gauge with a 12V source (momentarily since I didn't want to burn anything out), the needle behaved normally. 2). I bit the bullet and took the dash half apart to get at the back of the gauge. The yellow wire on the back of the gauge reads < 1V, the same voltage I get all the way back to the yellow wire at the tank. 3) The yellow/red wire appears to be the feed. No voltage when the key is off, 12V when the key is on. 4). I got about 700 ohms between the yellow and yellow/red wires at the gauge (after pulling the harness apart). A little hard to get a good number since the pins are set back and close together. 5). Next steps? It looks like it isn't too much of a stretch to remove the gauge at this point. Not sure about access to the other harnesses/lights. It may be easier to unscrew the nuts and remove the wires from the back of the gauge. 6) lots of fun removing the heater/vent/defroster cables and crawling under the dash! Thanks again for your help. John

Ok, thanks to both of you for the input. Looks like I have my work cut out for me. Not sure when I'll get to it. I may save it for next winter's project. I'm in upstate NY so there will be plenty of time to work on it then. Thanks once again for all the valuable input. John

Steve, thanks. To answer your previous question, the other gauges work fine so it looks like it is a fuel gauge issue. I did review the FSM on gauge removal but it still doesn't look like a lot of fun! Any particular reason why I shouldn't back feed the gauge? Thanks for you comments. John

Fantastic, great help and your explanation makes sense to me. Looks like I have to remove the gauge - something I'm not really looking forward to! I'm thinking of trying something. See if this makes sense to you. How about if I back feed a 12V source at the yellow wire by the Sender Unit? That should send current through the 'Second Heating Coil' and the 'First Heating Coil' then to ground. Shouldn't that make the needle move? Not sure what I'd do after that even if the needle does move but if it doesn't, wouldn't that mean that that one of the coils is bad (since that would not allow current to go to ground)? Thanks again for you description. Super helpful and if you know any tricks about removing the gauge, please let me know. As I mentioned, I reinstalled the dash and don't want to take it out again. My temporary fix will be to keep the tank reasonably full and watch how many miles I drive between fills. John

Steve, thanks for getting back to me so quickly. I did check for continuity as well as voltage at the dash. When I first encountered the problem, I thought I might have a broken/frayed wire from the dash to the tank but continuity was good. Also, the voltage of the yellow wire at the dash is also < 1 volt. It would seem that for some reason, the source of the yellow wire (the gauge?) is putting out only a small amount of voltage. Any other ideas? Thanks again, John

The fuel gauge on my 72 240z is not working. I've searched this site and have a question. Thanks in advance for any help you can offer. 1. It appears that the voltage at the yellow wire by the fuel tank should cycle between about 9 and 3 volts. I read less than one volt on that wire (it is not zero). I traced the wire back to the harness under the dash and at that point it is also <1 volt. Can someone verify that the voltage of the yellow wire by the tank does indeed cycle between about 9 and 3 volts? The yellow wire can be probed from behind the cover in the rear of the car that is used to change tail light bulbs. Any ideas on why I'm getting such low voltage and what could be wrong and fixed? It was working before I tore the car apart. I have reinstalled the dash a while ago and am not looking forward to messing with the gauge but I have a feeling that will be necessary at some point. Thanks again, John

I know this is an old listing. Do you still have this?