could this be causing an issue?

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PanGasket

PanGasket

has cork sides
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my sending unit has a ground strap and contacts at both ends are good but here's the catch. I have a larger 10ga wire going into something like a 14-16ga wire. now here's whats the goes on. my truck will say I have a quarter tank when I have no gas. its never read right since I've owned it.
 
Back in the early 90's i picked up a 76 d100 with only 46k miles on it from the original owner. Truck was so original it still had it's born with plugs, wires, belts and hoses... Fuel guage never read below a 1/4 and would never read full...... I'd fill it up and go 250 miles and stop for gas...never ran out that way.

I realize this does not answer your question but, it was the nature of the beast.
 
ragtopfury said:
Back in the early 90's i picked up a 76 d100 with only 46k miles on it from the original owner. Truck was so original it still had it's born with plugs, wires, belts and hoses... Fuel guage never read below a 1/4 and would never read full...... I'd fill it up and go 250 miles and stop for gas...never ran out that way.

I realize this does not answer your question but, it was the nature of the beast.
Click to expand...
sounds about right! :toothy10: It'll never read full no matter how much I dump in it
 
DarTT said:
my sending unit has a ground strap and contacts at both ends are good but here's the catch. I have a larger 10ga wire going into something like a 14-16ga wire. now here's whats the goes on. my truck will say I have a quarter tank when I have no gas. its never read right since I've owned it.
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heres a question for you, is your line grounded good to the car? its easier to run a wire to the tank corner outside of where they are welded so it don't leak
 
66plyValiant said:
heres a question for you, is your line grounded good to the car? its easier to run a wire to the tank corner outside of where they are welded so it don't leak
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I don't have a metal tank. Mine is plastic on my truck. and it is grounded to the frame
 
My 94 Ram Van has this issue and I also figured out that 250 miles from fillup is 1/2 tank in a 35 gal tank. I'm not in the mood to drop the tank to swap it out.
 
DarTT said:
I don't have a metal tank. Mine is plastic on my truck. and it is grounded to the frame
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oh on your truck, have you checked the voltage regulator in the dash? I assume thats your 1979 one you have?

the in tank senders rarely go bad on those unless rust gets it
 
DarTT said:
Nope. No voltage regulator on the dash. and my truck is a '74
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I can bet money it does too, my 1979 does and yours has the same dash in it, its a 3 prong 5 volt regulator that sends on/off power to achive 5 volts

even our old A bodies have that, in your truck its behind the gauges on the printed circuit board
 
DarTT said:
Nope. No voltage regulator on the dash. and my truck is a '74
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67Dart273 said:
I would bet you money it DOES
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66plyValiant said:
I can bet money it does too, my 1979 does and yours has the same dash in it, its a 3 prong 5 volt regulator that sends on/off power to achive 5 volts

even our old A bodies have that, in your truck its behind the gauges on the printed circuit board
Click to expand...

Found this wiring diagram for a 79 over at MyMopar

http://www.mymopar.com/downloads/79_Dodge_Truck_Wiring_Diagram.zip

In the drawing of the 79 cluster below, my horrid photo skills circled the 3 VL terminals. I think I got it right side up this time, LOL
 

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A bad limiter can prevent the gauge from going to full. Then a saturated float can also.
As for it going to empty... Does the needle return all the way home at switch off ? Empty isn't all the way home , empty is the first hash mark.
Different conditions equal different problems.
Hope this helps
 
67Dart273 said:
I would bet you money it DOES
Click to expand...

66plyValiant said:
I can bet money it does too, my 1979 does and yours has the same dash in it, its a 3 prong 5 volt regulator that sends on/off power to achive 5 volts

even our old A bodies have that, in your truck its behind the gauges on the printed circuit board
Click to expand...

67Dart273 said:
Found this wiring diagram for a 79 over at MyMopar

http://www.mymopar.com/downloads/79_Dodge_Truck_Wiring_Diagram.zip

In the drawing of the 79 cluster below, my horrid photo skills circled the 3 VL terminals. I think I got it right side up this time, LOL
Click to expand...
thanks guys! glad to be wrong. lol. how do I test it/find a new one?
RedFish said:
A bad limiter can prevent the gauge from going to full. Then a saturated float can also.
As for it going to empty... Does the needle return all the way home at switch off ? Empty isn't all the way home , empty is the first hash mark.
Different conditions equal different problems.
Hope this helps
Click to expand...

it returns to the empty mark at off. so it doesn't return home
 
DarTT said:
Nevermind. It will not even return to empty. it stays at current level of fuel
Click to expand...

something is wrong with the gauge needle itself then, most times on these trucks it scraps the face and doesn't have enough power running through the gauge to return or go higher
 
x2. From looking at the 79 wiring, and the comments from 66plyValiant, I'm sure you can troubleshoot these just like our A's

Basically what you have there is switched ignition feeding the regulator which has a ground terminal, and the output of the regulator goes to any gauge except ammeter, ie, temp, fuel, and oil if equipped.

All three gauges have the same movement electrically. This means you can use the same resistances to troubleshoot them.

A radio shack 25 ohm resistor ( 4x 100 ohm wired in parallel) after a minute or so with the key on should result in a 1/2 scale reading, substituted for the temp, or fuel sender.

If only one (fuel gauge) does not do so,.........bad gauge.

If both don't read correctly, probably bad instrument regulator, assuming wiring is OK.

Wiring and connections are also an issue.

But the needle not going down is a big clue.
 
Inside the gauge there is a tiny nichrome wire wound around a bimetal strip. The wire heats, the bimetal bows, the needle moves. sounds simple enough right ? It is.
We know it worked fine for a long time.
A closer look at that nichrome wire would reveal a extremely thin insulation. It is a spiral wound blend of silk and fiberglass. When the insulation burns away not only does the gauge short/die but the insulation ( like anything else that burns to ash ) should be found in the bottom of the gauge and look like black pepper.
That's not always what we find though. I've seen many of the nichrome windings intact except that the insulation has grown several times its original size. How ? Why ?
Nastiness from the air, especially tar from cigarette smoke, accumulates on the winding. Its drawn there by the heat. It restricts the movement of the bimetal just like a ace bandage would restrict the movement of your arm.
I'll bet my quarter this is what you will find inside your gauge. Sad part is it cant be cleaned. Just touch the stuff and it breaks off, equals dead gauge. Many times just polishing the bimetal and replacing the winding is all that's needed. Other times the bimetal must be replaced also.
 
RedFish said:
Inside the gauge there is a tiny nichrome wire wound around a bimetal strip. The wire heats, the bimetal bows, the needle moves. sounds simple enough right ? It is.
We know it worked fine for a long time.
A closer look at that nichrome wire would reveal a extremely thin insulation. It is a spiral wound blend of silk and fiberglass. When the insulation burns away not only does the gauge short/die but the insulation ( like anything else that burns to ash ) should be found in the bottom of the gauge and look like black pepper.
That's not always what we find though. I've seen many of the nichrome windings intact except that the insulation has grown several times its original size. How ? Why ?
Nastiness from the air, especially tar from cigarette smoke, accumulates on the winding. Its drawn there by the heat. It restricts the movement of the bimetal just like a ace bandage would restrict the movement of your arm.
I'll bet my quarter this is what you will find inside your gauge. Sad part is it cant be cleaned. Just touch the stuff and it breaks off, equals dead gauge. Many times just polishing the bimetal and replacing the winding is all that's needed. Other times the bimetal must be replaced also.
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between you and Del, I think I will have this figured out. If the gauge turns out to be bad, can I swap the guts of my oil pressure gauge in? I know that read correctly when it would stay hooked up to the bell sender.

Also Del, do I just put the resistor between the two posts or what do I do exactly? sorry to ask some real dumb questions, but I'd rather know exactly what to do. I'm not well versed at all in electrical but I can still figure some things out lol:D
 
The test resistors go from the sender wire to ground. You can start with temp as this is of course easy to get to under the hood. Hook the resistor from sender wire to ground, turn on the key, and leave it for a minute. If the temp gauge is way off, I'd assume you either have wiring troubles and or a bad instrument regulator in addition to fuel guage accuracy or damage.

On my 67, mine was a mess, and had several problems, typical of ANY of these

1--The pins on the PC board for the harness connector were loose or broken.

2--The fingers which form the socket for the limiter were not making good contact with the board, and needed jumpers soldered across.

3--The limiter itself was very "iffy" and I replaced it

4--On both gauges the "fake" tinnerman nuts were not making contact at the gauge studs, which must make contact with the PC board.

5--In addition, the wiring/ harness connections in the sender wires can be intermittent

6--Senders can be bad or intermittent.

I keep "preaching" LOL to guys to think of their gauges as a SYSTEM, and end to end system in one big package.

By checking with test resistors, OR checking resistance of one or the other and knowing what to expect, you can get an idea of how accurate things are.

This is supposed to be close to the resistances at empty (cold) -- 1/2 -- and full (hot)

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full
 
67Dart273 said:
The test resistors go from the sender wire to ground. You can start with temp as this is of course easy to get to under the hood. Hook the resistor from sender wire to ground, turn on the key, and leave it for a minute. If the temp gauge is way off, I'd assume you either have wiring troubles and or a bad instrument regulator in addition to fuel guage accuracy or damage.

On my 67, mine was a mess, and had several problems, typical of ANY of these

1--The pins on the PC board for the harness connector were loose or broken.

2--The fingers which form the socket for the limiter were not making good contact with the board, and needed jumpers soldered across.

3--The limiter itself was very "iffy" and I replaced it

4--On both gauges the "fake" tinnerman nuts were not making contact at the gauge studs, which must make contact with the PC board.

5--In addition, the wiring/ harness connections in the sender wires can be intermittent

6--Senders can be bad or intermittent.

I keep "preaching" LOL to guys to think of their gauges as a SYSTEM, and end to end system in one big package.

By checking with test resistors, OR checking resistance of one or the other and knowing what to expect, you can get an idea of how accurate things are.

This is supposed to be close to the resistances at empty (cold) -- 1/2 -- and full (hot)

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full
Click to expand...
went to an aftermarket temp gauge so that's a no go on that, but I can definitely get to my oil sender wire pretty easy and ground the resistor on my truck's body.

and I can definitely check the back of my cluster very easy. my entire dash pad is very easy to remove.

and I'll be sure to think of it more as a system now. right now my only gauges on there are my fuel and voltmeter or ammeter.
 
ah, You said the oil pressure gauge worked fine where the wire would stay on the sender.When that wire terminal falls off the sender and shorts to ground, the mechanical limiter will send full system voltage to all the gauges. That condition has also fried many gauges.
As for moving the gauges internals from one to another... Thats not doable.
You might move the screen from one to the other. The readings wouldn't be right though, unless the gauge is recalibrated to the fuel gauge screen.
 
RedFish said:
ah, You said the oil pressure gauge worked fine where the wire would stay on the sender.When that wire terminal falls off the sender and shorts to ground, the mechanical limiter will send full system voltage to all the gauges. That condition has also fried many gauges.
As for moving the gauges internals from one to another... Thats not doable.
You might move the screen from one to the other. The readings wouldn't be right though, unless the gauge is recalibrated to the fuel gauge screen.
Click to expand...
:eek:ops: well, thanks RedFish. Guess it looks like I will have to hunt down a new fuel gauge most likely
 
What year is the truck? I had an 84 that the board wore out and the the resistance for the gauge got messed up between 1/4 and E.
 
if you have an aftermarket heat gauge everything we've said so far is pretty much useless, it runs 12 volts without limiter and to the wires whomever ran were ever
 
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