240Z/240K Fuel Guage reading incorrectly

[bpilati]

Are you saying what I said is wrong? I don't follow.

[ez73]

I have the same problem as 28zero. replaced the sending unit with factory unit. still did same thing read empty when quite a bit of gas left in tank checked out gauge by disconnecting and then grounding guage checks out alright been told by several people problem is in harness somewhere. my 73 was in storage since late 80s corrosion in harness probale behind guage is the problem this causes added resistance. going to try to take the glove box out see if i could get to gauge that way d*** aka ez73

[Marty Rogan]

ez73,

Going through the glove box will likely destroy it, and those are NLA. You can disconnect all the heater cables and remove the entire heater panel with only 4 more screws. That will give you easy access to the gauge.

If the guage is reading empty when there is still gas in the tank, and you know your sender (float) is good, there is an adjustment screw on the sender, inside the tank. You could try adjusting it there. Make sure you only have about a 1/4 tank of gas though. You should change the "O" ring while its out so you don't have a leaking problem.

Let us know the final solution once you find it.

Marty

[bpilati]

ez73,

Going through the glove box will likely destroy it, and those are NLA. You can disconnect all the heater cables and remove the entire heater panel with only 4 more screws. That will give you easy access to the gauge.

If the guage is reading empty when there is still gas in the tank, and you know your sender (float) is good, there is an adjustment screw on the sender, inside the tank. You could try adjusting it there. Make sure you only have about a 1/4 tank of gas though. You should change the "O" ring while its out so you don't have a leaking problem.

Let us know the final solution once you find it.

Marty

Is it possible to purchase only the O-ring? Anyway my Z shop maintains that it's usually the sending unit that has a problem. I don't know, but my gage never reads exactly full or over full, but just a tad under when completely full. It's been too long to remember what it was like prior to this problem. Is it correct to assume that when the gage in on "E", there is still 2 or 3 gallons left as a reserve?

[Marty Rogan]

Sure, you can buy only the o-ring. Check the parts CD for the #. I would also buy the lock ring that holds in the sender, as you will probably destroy it trying to get the sender out.

I won't assume anything with these flaky gauges. Mine recently read 3/4 full and I ran out of gas. I reset the trip meter at fill-up. When I hit 200 miles, I fill it up again, just to be safe.

I would recommend that you clean up all the connections first. When you put it back together, just remember that the "G" post on the sender means GAGE, not ground. Those tricky, tricky Japanese!! !

Marty

[ez73]

thanks for replying Marty but the guage reads 2/3 full when filled to top and still has at least 40 miles of gas when the guage reads empty i don,t think adjusting the screw will fix my problem. How does one get the heater cables loose from the nacelle? when I had my stereo put in they unhooked one vent cable from the firewall area but did not take the faceplate off only moved it thanks d***

[bpilati]

Marty, maybe (God forbid) you need to kick the side of you Z to get the sender to plunk into the proper position so you won't run out of gas.

[Bambikiller240]

Having 40 miles of gas when the tank reads empty is completely normal for a Z car.

As for the gauge reading 2/3 when full, are you positive the tank is 100% full? Sometimes people (previous owners) will have disabled the fuel tank vent lines in such a way that air pockets are stuck in the tank, and the tank never gets it's full 15.9 gallons of fuel. Oh, you can see fuel in the filler tube, but there are air pockets (due to the vents being screwed up) that keep the tank from being completely filled.

[Zedrally]

Having 40 miles of gas when the tank reads empty is completely normal for a Z car.

.

I'm in complete agreeance with Carl on this.

Simply reset your tripmeter every time you fill the tank and you will never run out!

2/3=Full

Empty means I've travelled 340km around town or 400 in the country!

[bpilati]

Well, I believe my fuel vent lines are normal. The vapor tank, etc is hooked up, and I never saw anything unusual when I had the right interior panel removed once. The tubes on the left side of the engine compartment are all connected. I'm not sure of the gas mileage of my Z, and have never tested it to see if a full tank has been consumed.

[Bambikiller240]

Bryan: I was referring to the post by ez73.

My gauge barely reads full, but the tank will hold 15.9 gallons. (similar to your situation, I believe)

Readings of 2/3 full could be caused by air trapped in the tank . IMO, it's worth looking into, especially since it costs nothing but time to examine the vent lines and connections.

Your gauge (or even mine) reading "a tad under full" is quite a ways from ex73's gauge reading 2/3 when full, IMO.

[Daniel]

When I fought that demon I had these results. First I noticed my fuel guage would intermit move around like power/connection was poor. I could jumper across the two wires at the sending unit and the gauge would go full + and hold. I replaced my sending unit and tried the adjustment on it, only to have the same problem. I removed the guage and took it apart. I made a bench set up using the old sending unit. Things were testing ok and then I noticed on the rear of the guage is a contact point that looks just like your dist. points. I turned the lights off and put a spare bulb/socket in the guage. As the guage would drift wrong I would see a small blue arc between the point. I said ok I'll just soldier the points together as I had done to fix the drift on the temp/oil presure guage. On the bench fine.In the car full max all the time. I tried filing the points, jumper wires,the damn thing looks so simple .I bet I deinstalled/installed that guage about 45 times. I finally wound up with a guage that at 1/2 you needed fuel, full was way passed F. Iwent to the bone yard bought a used guage, lightly cleaned the much better contacts than what I had. Installed and the problem is gone. I do have 4 1/2 gallons at E due to the adjusting I did at the sending unit during my test. I can live with that. The moral of my story is start with the guage. The sending units I have pulled out have all been in good shape. The fuel being thrown at them keeps them very clean.