gas gauge question

[David K.]

Re: gas gauge question

David, you could use a borescope, and go down the filler neck and probley see the float. Most are waterproof. Ac delco makes one with a long cable. ARZ 1204. Then you can take a look at it.

[Richard M.]

Re: gas gauge question

I think the baffles in the tank would prevent you from seeing it.

This may be a thought to check the sender operation without tearing the cover all apart.......

Jack up the car with 2 floor jacks, one front frame x-member joint, the other rear frame x-member joint. This will tilt the car safely to one side or the other. Make sure the jacks are at 90* to the side frame rail, so their wheels will roll as you jack it up. The jacks will move in towards center of the car as it goes up.

Do this with the ohmmeter attached to the underdash wiring while you jack it up and down. Fuel will tilt and the level should change enough to move the float. The sender float pivot point is toward the passenger side, and the float is positioned about center of the tank, so I'd jack up the passenger side to see the most float movement.

[Dan D.]

Re: gas gauge question

Hi Rich again,

Yes, the wiring diagram does not show the fuse connections and I must have made the wrong assumption. Sorry.

But with the sender wire open circuit the gauge should go past full. Ground keeps it reading empty, and anything off of ground will swing the gauge toward full, with 30 ohms being full tank. Any extension past 30 ohms will put it past full. I have done this with my 57, which should be the same design. But this test is something Dave can do easily. I still think Dave's problem is the sender.

In your new post this morning I can see you are deep into this. Electronic, Ugh. Does maybe the electronic gauge work differently if the resistance goes past 30 ohms? I would think your original gauge would work as I described.

-Dan-

[Dan D.]

Re: gas gauge question

Okay Rich, I see your edit now. We both must have been busy typing at the same time. Its good we are both on the same page now.

-Dan-

[Richard M.]

Re: gas gauge question

Yup, I thought about it more this morning and came out to the shop and ran the test on the bench with my good original '61 set. Opened the sender wire and off she went past full. Ground = 0 ohms so that'll keep it pegged left. Open = high ohms so anything over 30 ohms pegs it right.

[David H.]

Re: gas gauge question

Looks like I have a lot of ideas to work with tomorrow.I will be trying all your thoughts on this and getting back to you.You guys are amazing. Thanks for all the feedback and ideas.

[David H.]

Re: gas gauge question

Did some testing today on this.Disconnected the single brown wire under the dash as instructed.With the key off, gauge stays under the E.With key on, gauge goes to past full.Assumption, gauge is ok.With ohm meter lead connected to the female end of the brown wire (unplugged from the male connector)and other lead connected to the black wire in the four gang connector under the dash, (plugged in) the reading is .08.(Here is where I had a question as to if it was the black wire or the black/white wire.)Can someone clarify this for me. I think it is suppose to be the black/white wire.So, I tested the brown wire to the black/white wire. The reading is .074. I also tested from the male brown wire to the black wire. The reading is .012. And then from the male brown wire to the black/white wire. The reading is .052. My thoughts are that there is not a grounding issue and the gauge is fine.Moving on, since I am not able to take it out and drive it in this winter wonderland of snow, I have moved on to jacking up the passenger side of the car to about 30 degrees and tried sloshing the gas in the tank. So far the gauge has not moved but am going to put the ohm meter on it to see if it changes.

[Richard M.]

Re: gas gauge question

David, I bolded my replies for easier reading.....

Did some testing today on this.Disconnected the single brown wire under the dash as instructed.With the key off, gauge stays under the E.With key on, gauge goes to past full.Assumption, gauge is ok.

Yes gauge may be "alive", but......

With ohm meter lead connected to the female end of the brown wire (unplugged from the male connector)and other lead connected to the black wire in the four gang connector under the dash, (plugged in) the reading is .08.
(Here is where I had a question as to if it was the black wire or the black/white wire.)Can someone clarify this for me. I think it is suppose to be the black/white wire.

Black/White....I mistakenly said (I think) Black in my previous post, sorry for the confusion. The black is the feed to the tail lights, the headlight switch was assumed off, therefore you were reading through the filament of the bulbs to ground, but basically ground.

So, I tested the brown wire to the black/white wire. The reading is .074.

This is reading the meter, female brown to blk/wt.

I also tested from the male brown wire to the black wire. The reading is .012.

Ignore this one for now as black is wrong, s/b blk/wt.

And then from the male brown wire to the black/white wire. The reading is .052.

Male brown is the sender wire at the tank. This is the important one, the one to leave connected for now. If you have empty tank it will be 0 ohms(basically what you're reading), 1/2 tank = 15 ohms, full tank = 30 ohms. These are approximates, within a few ohms.

If you can get your hands on a few resistors from a friend or a Radio Shack, you can connect them to the Black/White and the Female Brown(meter sender input) and you're gauge should read accordingly, as the values in the previous paragraph. If they have a 0 to 100 ohm potentiometer(variable resistor like a volume control) that would be ideal.


My thoughts are that there is not a grounding issue and the gauge is fine.

Maybe gauge is okay, but.....Not enough data yet to prove what's wrong. Your tests haven't proven the sender is good. How much gas is in the tank, if 5 gallons, ohms s/b apx 7, if 1/2 tank apx 15 ohms, etc.

Moving on, since I am not able to take it out and drive it in this winter wonderland of snow, I have moved on to jacking up the passenger side of the car to about 30 degrees and tried sloshing the gas in the tank. So far the gauge has not moved but am going to put the ohm meter on it to see if it changes.

And one other test is to now connect a known ground wire, from the cluster or even the battery Negative post to that Black/White connection to see if you get a change in readings. If so, you have a bad ground in the harness or at the tank ground wire attached to the sender. If you get no change..........

......I know you don't want to remove the tank cover, but if you need to check your sender you have to open it up. Remember, even if you get the car judged I don't think a "dot" or one point deduct, and they can't even really see it.

[David H.]

Re: gas gauge question

OK, connected a jumper wire from the neg post of the battery to the black/white wire in the four gang connector under the dash.No change in the gauge reading.

[Richard M.]

Re: gas gauge question

Okay, I think because your readings are so low, you have a dead short(0 ohms = Empty) at or in the sender.

I suppose you could have the wires reversed at the sender, but I didn't want to mention that before. Dark Brown looks like Black in dim light. I almost did that this morning when I reinstalled the sender in the '60 I was working on. The white tracer was underneath and I couldn't see it, until I twisted the wire.

If you get no change in your reading by tilting the car, another suspect is your brown wire at the sender possibly shorting the outlet pipe or Blk/Wt terminal, or the sender is internally shorted.

It takes 10 minutes to pull the cover and check wiring, and 10 minutes to pull the sender. Make sure battery power is off for safety.

Looks like it's fuel sender and fuel gauge week around here lately.

Rich

[David H.]

Re: gas gauge question

Well, I give in, the cover has to come off. Maybe next week. Again, thank you all for your input and help.I will post what I find.

[David H.]

Re: gas gauge question

Took the cover off yesterday and removed the sender. Moved the float up and own and the gauge worked accordingly.Removed the float for exam and found a crack in the brass float. Not at the soldered seam but in the actual brass material.Realized that I had a spare from the old sender and replaced it. Still not sure I am getting the correct reading as I am pretty sureI filled the tank a couple of days ago. Gauge shows half full.

[Richard M.]

Re: gas gauge question

David, If it's still removed you can test with a ohmmeter to be sure.

[Dan D.]

Re: gas gauge question

Dave, what I did is hook the sender up with it out of the tank. I moved the float up and down by hand and watched the gauge follow the sender position. At about the mid point on the sender, the gauge registered 1/2 full, so I figure it is close. Not sure just how accurate these gauges were from the git-go anyhow.

-Dan-

[David H.]

Re: gas gauge question

Got the gauge working and adjusted the float level after I filled the tank to the top. Hoping for the best.Thanks for all the input everyone.