Fuel Gauge

[hdixon]

I need help getting my fuel gauge to work I just replace the dash bezel with a new one on my 1969 C-10 and I have the wire from the fuel tank hooked up to the fuse panel at the top location that says fuel but can't get the gauge to move I did notice that when I turn the ignition on the gauge move a little in the wrong direction can anyone explain what I am doing in correctly

[AASmedic]

If everything worked before the bezel replacement then I would look to see if everything was reconnected securely on the new bezel. Does it have a good ground as well?

[hdixon]

I'm not sure if everything worked before I just purchase the truck and the bezel was old and had been painted so I replace it the only thing I see is one wire coming from the tank and it is hooked up at the fuse box I did not hook up anything to the bezel itself because when removing the old one there nothing hooked up to the gauge I put everything back the way it was not to say it was hooked up correctly before I replaced the bezel I thought everything worked though the bezel are there any other connection needed other than the one wire coming from the tank to the fuse box? were would it be grounded?

[VetteVet]

The fuel terminal on the fuse box has a tan wire running from it to the no.. 4 terminal on the cluster plug next to the pink power wire for the gauges. The pink wire runs from the fuse box cluster fuse. to the no. 3 terminal on the plug.





With the key on if you disconnect the fuel terminal wire, the gauge should read at the 2:00 O'clock position. If you then ground the fuel terminal on the fuse box, the gauge should go to dead empty.

[DarkFlounder]

Originally Posted by VetteVet

The fuel terminal on the fuse box has a tan wire running from it to the no.. 4 terminal on the cluster plug next to the pink power wire for the gauges. The pink wire runs from the fuse box cluster fuse. to the no. 3 terminal on the plug.

Attachment 1581884



With the key on if you disconnect the fuel terminal wire, the gauge should read at the 2:00 O'clock position. If you then ground the fuel terminal on the fuse box, the gauge should go to dead empty.

Do you have a high-res version of this diagram? I'm going to be wiring up a new instrument cluster (AutoMeter gauges in a repro bezel) and this would help greatly with the wiring.

[hdixon]

VetteVet thanks for all the help. I'm half way there I have and understanding from the fuel sending unit in the tank to the fuse box which I think is #4 on the fuse panel is #3 the cluster fuse and do I need to run a wire from the cluster to the fuel gauge or how dose it work from there

[VetteVet]

Look at this picture of the fuse panel and notice the blue arrows. They point to the pink 20 gauge wire from the cluster feed fuse to the no.3 on the cluster plug
which goes to the fuel gauge.

The fuel terminal shown by the other blue arrow has a tan wire from there to the no. 4 terminal on the cluster plug which goes to the fuel gauge also.




here's a different view of the fuse box with the fuel terminal on the other end.



If you don't have these two wires you will have to run them to the cluster plug.

Just for clarity, do you have the gauge cluster or the light cluster with the charging light. It makes a difference because the pink wire goes to the no. 7 terminal on the cluster plug on the light cluster.

[hdixon]

Still at it I was able to finally get power to the bezel plug coming from the cluster feed for the fuel gauge now it still shows empty how much fuel do you need to have in the tank for the fuel gauge to register the correct amount of fuel? I only have a couple of gallon in the gas tank however when I turn the ignition on and pull the plug from the tan wire off the fuse panel the gauge goes pass full when I reconnect it at that time it goes back to empty do this mean that it is hooked up correctly or not?

[VetteVet]

Originally Posted by hdixon

Still at it I was able to finally get power to the bezel plug coming from the cluster feed for the fuel gauge now it still shows empty how much fuel do you need to have in the tank for the fuel gauge to register the correct amount of fuel? I only have a couple of gallon in the gas tank however when I turn the ignition on and pull the plug from the tan wire off the fuse panel the gauge goes pass full when I reconnect it at that time it goes back to empty do this mean that it is hooked up correctly or not?

You can simulate adding fuel to the tank by wiring a resistor inline with the sending unit wire and the vehicle ground. If your float is in the bottom of the tank it will have zero resistance for the gauge, as the float rises it moves an arm across a resistor and gradually increases the resistance to the gauge. The range is 0 to 90 ohms from full down to full up.

The simple answer is to add a few gallons of gas to raise up the float, and the gauge should respond. If you weren't ready to add gas yet, you could take the wire off at the sending unit and get a few resistors with values in that range and connect them between the sending unit wire and a good ground. You should see different levels on the gauge.

As an example you could use a tail light bulb and ground the housing, then touch the sending unit wire on the filament connection on the end of the bulb. Depending on the bulb resistance you should get a reading on the gauge.

I don't know offhand what the tail light bulb resistance is but you can always use a multi meter to read the resistance on the bulb until you find one that reads in that range.

Here's a good diagram to help you understand how all that works.

[randy500]

Try this link to check your inside wiring harness. compare the idiot light guage panel connection to what you have in your truck. I just went through this...my truck had a 7 guage panel and nothing worked right, turn signals in dash acted weird and fuel guage didn't work. Turned out the truck did not originally have gauges. So I re-pinned the guage panel connection and now it works.

http://67-72chevytrucks.com/vboard/s...42#post5718242

[hdixon]

my truck did not have tachometer and I added one however I install a new bezel with the tachometer in it when you say you re-pin the circuit I don't understand just what you did but my turn signal work only if the truck is running if it is not running only one side works I just purchase this truck and I'm finding out it has a lot of issue

[hdixon]

I will try adding gas to the tank first because it is the simple thing to do I had the sending unit out of the tank and with my ohms meter I read 0 to 98 so that tells me that it is good will post something if the gas do the trick
thanks,

[66clow]

I'm Following, trying to figure mine out a well.

[hdixon]

let me know if you are successfully and I will do the same good luck

[RodnRudy]

It took 4 or 5 gallons of gas in my tank before the gage registered and then it moved up to about 1/4 tank.

[hdixon]

this information is a big help I thought that might have been part of my problem because when I pull the wire coming from the sending unit at the fuse panel the gauge goes pass full which I would think it had power going to the gauge coming from the fuse cluster feed I will try that and post it if that works thanks again for the info

[bstock1962]

Originally Posted by hdixon

this information is a big help I thought that might have been part of my problem because when I pull the wire coming from the sending unit at the fuse panel the gauge goes pass full which I would think it had power going to the gauge coming from the fuse cluster feed I will try that and post it if that works thanks again for the info

If I understand correctly, sounds like your gauge always shows empty except when you unplug the wire. I would add more gas so you have at least five gallons, then try the tests I listed previously. If it passes those tests, and the gauge still shows empty with wire connected, your sending unit float might have a hole in it filling with gas (and sinking).

[mister.freeze]

Mine is stuck past full. It started to move the other day, but then went back past full. That means an open between the fuse box and sending unit?

[mister.freeze]

I have 12v at the gauge (pink wire) and continuity between the other pole on the gauge and the sending unit. The gauge reads just past full. When I pull the wire at the sending unit, the gauge goes way past full to the 3 o'clock position. When I let it sit, the needle will drop a little below full, but move up past full again when I turn it on. All this is regardless of how much fuel is in the tank. years ago, it worked correctly, but not since coming out of storage. So... what went bad? Gauge or sending unit? Or something else? Please help!

[bstock1962]

The easiest way to troubleshoot fuel gauge problems is at the sending unit. Don't mess with the cluster or fuse box until you do this first: Slide your seat forward, and with the key on disconnect your tan wire at the sending unit. Your gauge should now read about 3:00. Now ground the tan wire against the top of the sending unit, or the fuel tank, or a known good ground. The gauge should now go to empty. If those two steps work, everything is working properly all the way back to the gauge.

That tells you the problem is in the sending unit. I have pulled out sending units and cleaned them up more than once at they work fine.

[mister.freeze]

Slide the seat forward?!

That's very helpful. I'll try grounding the tan wire next. If that checks out, I'll try and mess with the sending unit next week when the tank is near empty again. Those aren't terribly cheap to replace, are they?

[bstock1962]

Originally Posted by mister.freeze

Slide the seat forward?!

That's very helpful. I'll try grounding the tan wire next. If that checks out, I'll try and mess with the sending unit next week when the tank is near empty again. Those aren't terribly cheap to replace, are they?

Slide the seat forward to get access to your sending unit. I'm assuming your tank is behind the seat. You can do those tests regardless of how much gas is in the tank. Looking at your symptoms, I'm guessing the sending until is gummed up (like varnish) and can't move up/down correctly.

[mister.freeze]

Oh!! I've got a Blazer.

The gauge always shows about 1/2" past full, not near empty, except when I disconnect the tan wire from the sender. Then it goes another inch past full to about the 3:00 position.

I fill up weekly, between 22 and 32 gallons. The tank holds 36, so I go from pretty empty to full with no change in the gauge reading

[bstock1962]

Originally Posted by mister.freeze

Oh!! I've got a Blazer.

The gauge always shows about 1/2" past full, not near empty, except when I disconnect the tan wire from the sender. Then it goes another inch past full to about the 3:00 position.

I fill up weekly, between 22 and 32 gallons. The tank holds 36, so I go from pretty empty to full with no change in the gauge reading

We're mixing up troubleshooting two different vehicles. The empty tank comments were for HDIXON's 69 C10.

Since yours is a blazer, it's going to be tougher to ground your tan wire. Maybe there is access to reach it on top of your tank? I'm not sure how it's laid out. You might have to drop your tank to test it. But you likely need to drop your tank anyway because I think your sending unit is gummed up from sitting idle for years. But cleaning it will probably fix it.

[mister.freeze]

I can reach the tan wire and disconnect it easily enough. But yes, to access the sender, I havve to drop the tank, which is easy enough when empty. That's why the delay until next week: it will be close to empty from commuting all week.

What's best to clean the sender? Carb cleaner?