Still having issues with my gas gauge

[frog210]

Well most of yall now by now about my gas gauge lol
i just cant get it to work
I installed a new tank and a sender
cleaned the ground for the sender real real good
the green wire on the sender cleaned it with some connector cleaner
but still can get a reading
I have 3 different gauges
One is the factory or i think the factory gauge of the truck
One is off a 83-87 small jimmy or blazer not the big one the little ones
the last one i got from a member here with a few other gauges
Okay well the factory gauge stays at the 1/8th of a tank
the one off the jimmy starts at e then goes up slowly to the 3 o clock position
the one i got from a member goes straight to the 3 o clock position
the sender is grounded, and everything is seated
idk what to do anymore
could i just run the wires straight from the sender and 12v and ground to gauges?
Thanks for any help
frog

[Stepside84]

I have done all the same things as you and im still stuck at 3 oclock, i even added a ground lol. Didnt help. Hopefully theres another solution
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[motornut]

i'd check the sender wire,maybe run a temp/tester wire sure
it will go like that if the sender wire is off
if it's working right and you ground the sender wire it will go to E
my jimmy has an "extention " wire (looks stock)from halfway down the frame

[hatzie]

3:00 means the sender signal isn't reaching the gauge.

You state the ground from tank/sender to frame is good.

I am assuming this is your 1974?? You didn't state the year in your post.

The sender wire is Green??? Maybe Light Blue? Originally it had 73-80 Dual tanks? The 73-80 single tank systems usually used Tan for the sender.
On the 73-80 dual tank systems a DPDT dash switch selects which sender is in use. If the truck has been "converted" to a single tank the wiring is probably still there.

Is the dash switch good? or unplugged?? or missing with the plug dangling??? or plug is cut off and wires left dangling????

Have you checked the sender to tank switch wire for damage?
Is the tank switch working?
Is the Tan wire that runs from the tank switch center terminal, through the tank switch wiring grommet, into the firewall bulkhead connector OK?
Have you checked the wire that runs inside the cab from the bulkhead plug to the instrument cluster plug for damage?
Are the 3 cluster clips making firm contact with the studs on the gauge?

I just posted my scans of the 1974 GM wiring diagrams.

[slam59]

mines stuck at 3/4 of a tank...and when you pull off a gauge from another truck, are they supposed to be able to move ( the needle) and stay where u move it, or are they supposed to be like the speedometer and after turning or moving, go back to E mark?

[88Jimmy4x4]

On my 1976 pass side single tank, the sending uint wire is one solid tan wire from pin 13 of the firewall bulkhead all the way to tank sending unit. This wire is part of the engine wire harness and travels behind engine, then down with starter wires and then over to frame rail.

It could be possible you have a break/short in that wire somewhere. I would disconnect engine harness at firewall and check continuity (ohm) of the wire from sending unit to pin 13. If its bad you could easily run a new wire from tank to the firewall bulkhead. Checking it this way you would know if the problem is external of the truck or internal (dash, harness etc).

I would also check continuity of your sending unit connection to ground (frame), thats very easy to do.

[motornut]

Originally Posted by slam59

mines stuck at 3/4 of a tank...and when you pull off a gauge from another truck, are they supposed to be able to move ( the needle) and stay where u move it, or are they supposed to be like the speedometer and after turning or moving, go back to E mark?

stay

[frog210]

Sorry ya mi truck is a 74 I have not checked the tank switch its been running on the left tank only its a dual tank
My sender wire and ground are connected mi sender wire is green and black for ground
I will have to check the wire connector at the plug
I also added a mother ground behind the dash but no help
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[hatzie]

Probably the dash switch. If it's there, working, and hooked up, switching to AUX should complete the RH tank gauge circuit.

[frog210]

well guys
i think i made some progress
found a tan, brown wire running from the valve selector?
up the frame almost to the cross member but was cut
i then found this wire with i guess you can say alternator wire bundle
that was cut too they looked the same so i connected them
and well this is what happens now
when i switch to the left from the switch it goes to the 8 o clock position
then when i switch to the right tank it goes to the E
i use the left tank, i dont use the right tank

[Skunksmash]

Sounds to me like you need to test your resistance in your sender wire leading to your gas gauge. Test at the wire that plugs right into the back of the gauge. Follow the lines on your printed circuit on the back of your gauge cluster all the way to the wire that the plug itself plugs into. That will of course be the fuel sender wire. A factory GM fuel sender from these years of trucks will operate on a 0-90 Ohm resistance reading. Or was it milli-ohms? Or the other one? Someone help me out here. Can't remember but its some degree of resistance measured in Ohms and the operational numbers are between 0 and 90. 0 indicates an empty tank, and 90 indicates a full tank.

So what would your Ohmmeter (or just a voltage meter with an ohms setting) read if you had half a tank? That's right, 45 ohms. Or right there in that area somewhere depending on exactly how much fuel you had in the tank of course.

So what you need to do is take your meter and test your wires for the proper resistance. Once you find that the wire is in fact reading the right ohms for roughly how much you have in that tank, then you've just confirmed that your wire isn't grounding out somewhere and your gauge is getting a good signal from the sender. Now time for my personal opinion. It ain't pretty lol.

All those stock gauges belong in a garbage can. Get you a good aftermarket gauge (I used autometer) as they actually work to filter out some of the stuff you don't want like the wavy needle, and they are more accurate as well.

[frog210]

Originally Posted by Skunksmash

Sounds to me like you need to test your resistance in your sender wire leading to your gas gauge. Test at the wire that plugs right into the back of the gauge. Follow the lines on your printed circuit on the back of your gauge cluster all the way to the wire that the plug itself plugs into. That will of course be the fuel sender wire. A factory GM fuel sender from these years of trucks will operate on a 0-90 Ohm resistance reading. Or was it milli-ohms? Or the other one? Someone help me out here. Can't remember but its some degree of resistance measured in Ohms and the operational numbers are between 0 and 90. 0 indicates an empty tank, and 90 indicates a full tank.

So what would your Ohmmeter (or just a voltage meter with an ohms setting) read if you had half a tank? That's right, 45 ohms. Or right there in that area somewhere depending on exactly how much fuel you had in the tank of course.

So what you need to do is take your meter and test your wires for the proper resistance. Once you find that the wire is in fact reading the right ohms for roughly how much you have in that tank, then you've just confirmed that your wire isn't grounding out somewhere and your gauge is getting a good signal from the sender. Now time for my personal opinion. It ain't pretty lol.

All those stock gauges belong in a garbage can. Get you a good aftermarket gauge (I used autometer) as they actually work to filter out some of the stuff you don't want like the wavy needle, and they are more accurate as well.

Everyone has a right to their opinion i just want to get all my wires and circuits right, in the future i want to get a dakota digital
Will have to try with my multimeter tomorrow thanks

[88Jimmy4x4]

told you in above reply the wire was tan lol

Im glad your making progress.....you will get it eventually

[hatzie]

Is there voltage on the sender wire? That's the only way I know to make the gauge read below E.

A tan wire runs to the valve on the frame? Has your truck been retrofitted with an '80s motorized valve?

This is the 1974 factory dual tank schematic from the 1974 wiring manual.

[frog210]

okay well i guess its off under the truck tomorrow then
how can you tell which tank is the aux? driver or passenger?

Will try to get some more pics
side question
i took all my wires apart, they were wrapped in electrical tape
im still working on the electrical, but i dont want to leave it just exposed
should i re wrap it all in tape or zip tie them... dont want to really put loom next to a hot engine

[hatzie]

Aux is the tank that's activated when the solenoid has power. The dash switch selects the sender as well as powering the solenoid in the AUX position.
According to the GM wiring diagram the AUX tank sender has a LT BLU sender wire and the primary tank has a TAN sender wire.

That diagram came out pretty grainy after the Board Upload software cut the resolution in half. I scanned 400dpi PDF files of the 74 Chevrolet Light Truck Wiring manual along with the 74 Service and 74 Overhaul manuals. They can be found in the linked thread in my signature.

[frog210]

okay guys well i went over the wiring and everythings correct
sorry i was wrong about the wire that i thought went to the selector valve
This is the way its routed on my truck exactly
im gonna check the fuel tank switch right now
let me know if its right

[Skunksmash]

Originally Posted by hatzie

That diagram came out pretty grainy after the Board Upload software cut the resolution in half. I scanned 400dpi PDF files of the 74 Chevrolet Light Truck Wiring manual along with the 74 Service and 74 Overhaul manuals. They can be found in the linked thread in my signature.

Yeah I don't like the way this board is always doing that. Its a big hindrance when trying to read what people are putting up there sometimes.

[frog210]

okay guys well heres a update
i think i finally got it
What i did was switch out gauges
if i bench tested it right the gauge i had in their was bad
swapped in another gauge i i get these readings now
left tank around 3/4 of a tank
right tank reads about the 3 o clock position(it might be a bad ground)
i havent been able to drive the truck around to find out if i fixed it or not


---
Also i painted my gauge needles with some family dollar nail polish to make it all match lol
the pic without the plastic is the before pic
and the one with the plastic is the after pic


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another side question
the last pic
this is behind my ac control switch i dont see no plug for the 3 prongs sticking out or the other little prongs look like for a vacuum??
TIA

[story]

Frog that exactly what my truck does... If it's on the passenger side tank it work fine... as soon as I flip it to the driver side tank the gas gauge is at 3:00.Don't know if this helps you? But I never use the drivers side and it's always empty.

[motornut]

another side question
the last pic
this is behind my ac control switch i dont see no plug for the 3 prongs sticking out or the other little prongs look like for a vacuum??

looks like heat/AC controls vac lines...to a female plug of them
and the speed switch....is it heat only(non AC)?

[frog210]

Okay goes well guess what???...
.
.
.
My gauge works thanks all you guys for the help
My sender is a spectra and i know i saw somewhere here that the sender makes the needle on the gauge bouncy, it is when i drive the truck it bounces like almost a 1/4 or more,
I left the truck on when i put gas in and was watching the gauge
, it went up while i was putting the gas in it, went up a little pass the full mark, so i will have to see how it works now
have to see where the new full is at and Empty
but im happy
Thank yall for yalls help

[Skunksmash]

Its a combination of the sender AND the fuel gauge. GM really screwed the pooch on that one. For example, mine used to be the same way. The needle was wavy to the point that the gauge was almost unusable at times. But then I put in an autometer fuel gauge, and it stopped waving. Now it does still move. But when it does its slow, and not nearly as frequently. So at least I was able to cut the fuel gauge out of the wavy needle equation.

As for getting the rest out, I'm thinking you'd have to go with a newer tank or something with way better baffles. Cause you can spend a lot of money on a good ACdelco brand sender for the tank, and that's probably the best one you can buy. Too bad that's likely what they came with lol

[hatzie]

Originally Posted by Skunksmash

Its a combination of the sender AND the fuel gauge. GM really screwed the pooch on that one. For example, mine used to be the same way. The needle was wavy to the point that the gauge was almost unusable at times. But then I put in an autometer fuel gauge, and it stopped waving. Now it does still move. But when it does its slow, and not nearly as frequently. So at least I was able to cut the fuel gauge out of the wavy needle equation.

As for getting the rest out, I'm thinking you'd have to go with a newer tank or something with way better baffles. Cause you can spend a lot of money on a good ACdelco brand sender for the tank, and that's probably the best one you can buy. Too bad that's likely what they came with lol

A good gauge guy can fix the fluttery gauge by injecting a gel to damp it.
Th C2 Vette guys mention it in this article...
http://www.lbfun.com/warehouse/tech_...nding_unit.pdf

[frog210]

I wondered if i could use heavy grease
i dont know any good gauge guys around here in my area
unless their some people yall can recommended me to online