Is it normal for the gas gauge to swing from showing 3/4 full to 1/4 full and back and forth while driving? Also, the tank doesn't want to fill up at the pump....is there any type of vent that would (when/if plugged) not allow the second tank to fill (possibly not allowing the cross over tube to flow)?
Is it normal for gas tank
- Thread starter Growler
- Start date
cadreamn67
Platinum Forum Member
- Messages
- 608
That gauge swing does not seem normal.
There is a vent tube of sorts from the top of the driver's side tank that crosses over to the side of the filler on the passenger side of the car. Often that tube develops cracks with age and causes a gas fume smell in the car. I am not aware of it ever getting plugged. But if it did you would have air pressure build up in the driver side tank as you put gas in that would keep it from filling fully.
Gene
There is a vent tube of sorts from the top of the driver's side tank that crosses over to the side of the filler on the passenger side of the car. Often that tube develops cracks with age and causes a gas fume smell in the car. I am not aware of it ever getting plugged. But if it did you would have air pressure build up in the driver side tank as you put gas in that would keep it from filling fully.
Gene
- Messages
- 4,330
The gauge is not behaving.. check its grounds, they often cause issue, voltage stabiliser is worth a look.
As for th etank, the only vent is the rubber one that runs between the tanks up the top around the boot.. that would not stop it filling. Have you tapped on the oposite tank to hear how much fuel is in it?
As for th etank, the only vent is the rubber one that runs between the tanks up the top around the boot.. that would not stop it filling. Have you tapped on the oposite tank to hear how much fuel is in it?
- Messages
- 2,968
It has ghosts !!! Or, if it still does it after a good séance, check the grounds and send hate mail to Lord Lucas. If the temp gauge is also weirding on you, check the voltage stabilizer like Mike suggested. Amen
If there is a problem with the voltage stabilizer the temp gauge will make similar swings in unison with the fuel gauge.
The sending unit is the likely culprit here. I had a similar problem with mine. Inside the sending unit is a spring arm that wipes across a winding of resistance wire. What I found with mine is that the spring arm had lost enough tension that it was making intermittent contact with the resistance wire winding. How I solved the problem was to carefully bend the spring arm to give it more tension.
The sending unit is the likely culprit here. I had a similar problem with mine. Inside the sending unit is a spring arm that wipes across a winding of resistance wire. What I found with mine is that the spring arm had lost enough tension that it was making intermittent contact with the resistance wire winding. How I solved the problem was to carefully bend the spring arm to give it more tension.
Thanks gents. No problem with the temp guage. I will check the ground, although I had gone through each guage and wiring when I re finished the dash, so I think it may be the sending unit as described...but as mentioned, I'll check all avenues.
Is there any additional info on the checking the sending unit? Location, steps for removal & repair?
Thanks,
Josh
Is there any additional info on the checking the sending unit? Location, steps for removal & repair?
Thanks,
Josh
- Messages
- 2,968
More bruised knuckles
A bit of caution on the sending unit issue; besides the fact that it will eat up some time getting at the darned thing in the first place. Once you have the unit in your hand, you will note the "blow proof" cover over the resistance arm. Take careful note of the contact's width as it is specifically designed to touch more than one coil at all times. This is a built in safety design to limit any arching potential. When bending the arm for more tension, make sure to maintain the flat broader contact surface . . . . . .
A bit of caution on the sending unit issue; besides the fact that it will eat up some time getting at the darned thing in the first place. Once you have the unit in your hand, you will note the "blow proof" cover over the resistance arm. Take careful note of the contact's width as it is specifically designed to touch more than one coil at all times. This is a built in safety design to limit any arching potential. When bending the arm for more tension, make sure to maintain the flat broader contact surface . . . . . .
There isn't a distinct ground wire going to the sending unit, it is grounded directly to the tank. The only ground wire that can be faulty in this system is the ground wire going to the fuel gauge. If the light in the fuel gauge is working then this is likely not your problem, but check the ground connection anyway because it is an easier fix. Also check the connections on both ends of the wire going from the sending unit to the fuel gauge, make sure that they aren't loose or corroded. You can test both the gauge itself and the wire by grounding the wire at the sending unit. With the ignition switch on, the gauge should slowly move all the way to full and stay there. If everything is good so far, you found your problem, it's the sending unit.
To get the sending unit out you must first remove the left inner trunk panel. Then remove the two bolts holding the left trunk support arm to the trunk lid so that you can release the tension and remove the spring. Unplug the wire on the sending unit. There is a collar holding the sending unit in, take a long screwdriver and place it against one of the tabs on the collar on the RIGHT side of the sending unit and gently tap it with a hammer turning it counter clockwise about a quarter of a turn to loosen the collar. Once the collar is removed the sending unit comes out of the top. BE GENTLE and careful pulling it out, you will have to go through some contortions! Installation is the reverse of this procedure but getting that collar tight is a major pain.
While the sending unit is out of the tank, this is a good time to check the float to make sure that there isn't any gas inside it. If there is, you have a pin hole in the float.
A bit of caution on the sending unit issue; besides the fact that it will eat up some time getting at the darned thing in the first place. Once you have the unit in your hand, you will note the "blow proof" cover over the resistance arm. Take careful note of the contact's width as it is specifically designed to touch more than one coil at all times. This is a built in safety design to limit any arching potential. When bendin. . . . . .
Arching in the fuel tank?
blow proof I sure hope its a grounding issue.This is a non-issue.Arching in the fuel tank?
First, the gas tank can't explode due to electrical arcing in the tank. There is gas vapor inside the tank. The vapor being heavier than air displaces the oxygen and nitrogen so you are left with liquid gas and gas vapor. Without oxygen and nitrogen there can be no ignition. The only way that there could be an an explosion would be if one were to pump air into the tank. This is basic chemistry & physics 101 guys.
Second, the fuel level system uses very little amperage and the voltage available at the sending unit rheostat is quite small since it it is wired in series with the resistance wire in the fuel gauge, so any arcing/sparking will be very small. Anyway, if there is any arcing/sparking it is already happening NOW because he is getting an intermittent connection.
Third, the rheostat is inside it's own metal box inside the gas tank, the box acts as a spark arrestor.
I think that Myth-Busters had an episode that addressed this sort of thing. They shot at the tank, they stuffed a gas soaked rag down the fuel filler neck and lit it, and I think they even threw lit matches down into the fuel filler neck. Finally, the only way that they could get the fuel tank to explode was to attach explosives to it.
Last edited:
- Messages
- 2,968
Ditto BUT
Just like raising a teenager, trust but verify each & every time. The wee box that the rheostat is encased in is technically called a "blow proof cover". And, YES, I have seen one arc while being worked on. . . . . . The lack of oxy in an enclosed tank is sound judgement.
Just like raising a teenager, trust but verify each & every time. The wee box that the rheostat is encased in is technically called a "blow proof cover". And, YES, I have seen one arc while being worked on. . . . . . The lack of oxy in an enclosed tank is sound judgement.
I believe the problem is with the gauge. I disconnected the wire at the sending unit and grounded it directly to the car....gauge still went up and down (possibly not a much but still over 1/3 to 1/2).checked the connection at the gauge and bullet connection as well the ground at the gauge. Then just to make sure, ran a new wire from gauge to ground and still had the problem.....so it must be the gauge right (fyi temp gauge and all bulbs are good)?
- Messages
- 2,968
It should float
Most of the time, it's the float or float arm that's the problem. If you go thru the trouble of nursing the piece out, connect it & ground it and watch the dash as you lift the float.
Most of the time, it's the float or float arm that's the problem. If you go thru the trouble of nursing the piece out, connect it & ground it and watch the dash as you lift the float.
- Messages
- 2,968
Yer right
I was having a senior moment and responding to another almost identical customer issue. Try a donor dash gauge next.
I was having a senior moment and responding to another almost identical customer issue. Try a donor dash gauge next.
aussie rob
Bronze forum user
- Messages
- 21
The only trouble is you don't know what you are buying either... It may be worse than what you already have. On the flip side it can also be better.
It seems a voltage regulator
It seems that a voltage regulator was the culprit. I took the gauge out to the instrument refurbisher who tested it and it worked properly. Since, I had ruled out the sending unit by by-passing it and the wiring by grounding the gauge directly to the car and still having the problem, I swaped out the voltage regulator and it is now rock steady and accurate. FYI, it seems that the temp gauge doesn't react as quickly or easily as the gas gauge and therefore the diagnosis was a bit trickier (although with all your help still easy).
You should know that the instrument man informed me that although it is common practice to test the gauge by grounding it directly, he warned that one can damage it by doing so, as some guages react fast and hard to the circut it can actually break the needle....as appearantly even with a full tank, the sender still has some resistance.
Another problem down (and for only $20)...Now to look into my brake that locked up on me and hot wheel
It seems that a voltage regulator was the culprit. I took the gauge out to the instrument refurbisher who tested it and it worked properly. Since, I had ruled out the sending unit by by-passing it and the wiring by grounding the gauge directly to the car and still having the problem, I swaped out the voltage regulator and it is now rock steady and accurate. FYI, it seems that the temp gauge doesn't react as quickly or easily as the gas gauge and therefore the diagnosis was a bit trickier (although with all your help still easy).
You should know that the instrument man informed me that although it is common practice to test the gauge by grounding it directly, he warned that one can damage it by doing so, as some guages react fast and hard to the circut it can actually break the needle....as appearantly even with a full tank, the sender still has some resistance.
Another problem down (and for only $20)...Now to look into my brake that locked up on me and hot wheel
- Messages
- 4,330
Well i got it on the voltage stabiliser/reg.. you say you have a locking brake and hot front wheel..
your car was in long term storage.. i'd put good money that it will be the front brake hoses.. they look fine on the outside but perish internally.. when you apply they colapse and the brakes lock on and dont realease properly.
If you have the orignal hoses swap them out.. also what fluid is in the brakes.. make sure it is correct... lots of us avoid silicone fluids.. for reasons of seals and hoses not being ready for them.. and the suspicion that it kills the hydraulic brake light switch.
your car was in long term storage.. i'd put good money that it will be the front brake hoses.. they look fine on the outside but perish internally.. when you apply they colapse and the brakes lock on and dont realease properly.
If you have the orignal hoses swap them out.. also what fluid is in the brakes.. make sure it is correct... lots of us avoid silicone fluids.. for reasons of seals and hoses not being ready for them.. and the suspicion that it kills the hydraulic brake light switch.