Erratic Fuel Guage
10-09-2008, 10:09 PM
#1
Rennlist Member
Thread Starter
Erratic Fuel Guage
The fuel guage has never read full since I've owned the car and today on a good trip (+400kms) the needle starting wavering between E and 1/4 when it was still 1/2 full.............I know this because I thought something else may be wrong so I stopped and filled up again.
I believe the guage has a rehostat that can be adjusted so it does read full correctly?
Any thoughts on the 'wavering' is appreciated.
I believe the guage has a rehostat that can be adjusted so it does read full correctly?
Any thoughts on the 'wavering' is appreciated.
Last edited by the flyin' scotsman; 10-09-2008 at 10:51 PM.
10-09-2008, 11:03 PM
#4
Burning Brakes
The fuel guage has never read full since I've owned the car and today on a good trip (+400kms) the needle starting wavering between E and 1/4 when it was still 1/2 full.............I know this because I thought something else may be wrong so I stopped and filled up again.
I believe the guage has a rehostat that can be adjusted so it does read full correctly?
I believe the guage has a rehostat that can be adjusted so it does read full correctly?
I'd do this and see if it fixes the problem before pulling the sender because it's easy and cheap (oh, and it worked on my car).
Matt
10-09-2008, 11:08 PM
#5
Rennlist Member
Thread Starter
Thx all..............Matt I'll check it out in the morning; my biggest concern was that I was loosing fuel somewhere else; yikes!!!
10-09-2008, 11:25 PM
#6
Rennlist Member
As suggested, possibly the sender. My gauge read 3/4 when full also. I adjusted the needle.
A quick test for wiring and gauge operation:
-Disconnect sending unit and turn ign on, should read empty.
-With test light, check for dim light on one of the terminals. Should be violet and black wire on your car. Should be very dim, fuel circuit is low voltage.
-Ground wire gauge should peg full.
Hopefully this can give you some direction
http://www.nichols.nu/tip325.htm
A quick test for wiring and gauge operation:
-Disconnect sending unit and turn ign on, should read empty.
-With test light, check for dim light on one of the terminals. Should be violet and black wire on your car. Should be very dim, fuel circuit is low voltage.
-Ground wire gauge should peg full.
Hopefully this can give you some direction
http://www.nichols.nu/tip325.htm
10-09-2008, 11:32 PM
#7
Rennlist Member
Thread Starter
thx Zeus............when you adjusted the needle did you pull the guage cluster and adjust the 'stat?
I'll try the sender tests tomorrow weather permitting............its below zero at nights now
I'll try the sender tests tomorrow weather permitting............its below zero at nights now
Trending Topics
10-09-2008, 11:39 PM
#8
Rennlist Member
With a completely Full tank, I pulled cluster and removed gauge. I removed the needle and adjusted. Works perfectly, low fuel light comes on with approximately 3.5 gals still in tank.
10-10-2008, 01:45 PM
#9
Rennlist Member
Thread Starter
A quick test for wiring and gauge operation:
-Disconnect sending unit and turn ign on, should read empty.
-With test light, check for dim light on one of the terminals. Should be violet and black wire on your car. Should be very dim, fuel circuit is low voltage.
-Ground wire gauge should peg full.
Hopefully this can give you some direction
http://www.nichols.nu/tip325.htm
-Disconnect sending unit and turn ign on, should read empty.
-With test light, check for dim light on one of the terminals. Should be violet and black wire on your car. Should be very dim, fuel circuit is low voltage.
-Ground wire gauge should peg full.
Hopefully this can give you some direction
http://www.nichols.nu/tip325.htm
ign off: zero volts between grd and both purple and yellow wires
ign on: +2v beween purple and grd; batt voltage yellow and grd.
Grounding the purple wire with ign on pegs the gauge to complete full.
Given the lateness in the season (icy mornings already) I'll remove pod and gauges in the winter for complete repair..........cheers
10-10-2008, 02:31 PM
#10
Captain Obvious
Super User
Super User
Malcolm,
I had this same with my '85. In my case a corroded ground terminal at he sending unit was the problem. After cleaning it with steel wool, the fuel gage started working like it should.
Check the connector at the sending unit (under the trunk carpet and bellow the plastic plug) before tearing the gauge cluster apart.
I had this same with my '85. In my case a corroded ground terminal at he sending unit was the problem. After cleaning it with steel wool, the fuel gage started working like it should.
Check the connector at the sending unit (under the trunk carpet and bellow the plastic plug) before tearing the gauge cluster apart.
10-10-2008, 02:38 PM
#11
Rennlist Member
Confirmed wiring and gauge op:
ign off: zero volts between grd and both purple and yellow wires
ign on: +2v beween purple and grd; batt voltage yellow and grd.
Grounding the purple wire with ign on pegs the gauge to complete full.
Given the lateness in the season (icy mornings already) I'll remove pod and gauges in the winter for complete repair..........cheers
ign off: zero volts between grd and both purple and yellow wires
ign on: +2v beween purple and grd; batt voltage yellow and grd.
Grounding the purple wire with ign on pegs the gauge to complete full.
Given the lateness in the season (icy mornings already) I'll remove pod and gauges in the winter for complete repair..........cheers
10-10-2008, 03:19 PM
#13
Rennlist Member
Thread Starter
Malcolm,
I had this same with my '85. In my case a corroded ground terminal at he sending unit was the problem. After cleaning it with steel wool, the fuel gage started working like it should.
Check the connector at the sending unit (under the trunk carpet and bellow the plastic plug) before tearing the gauge cluster apart.
I had this same with my '85. In my case a corroded ground terminal at he sending unit was the problem. After cleaning it with steel wool, the fuel gage started working like it should.
Check the connector at the sending unit (under the trunk carpet and bellow the plastic plug) before tearing the gauge cluster apart.
10-10-2008, 05:29 PM
#14
Team Owner
the sending unit is kind of pressed into the support at the bottom of the tank, so it may take a hardy pull to get it out..
That said if the nuts are rusted on the bottom of the sender dont try to loosen them you will damage the wires that run up the inside of the sender and permanently damge them (IE keep an eye on the stud that the nut is screwed onto if its turning then permanent damage will occur)
That said if the nuts are rusted on the bottom of the sender dont try to loosen them you will damage the wires that run up the inside of the sender and permanently damge them (IE keep an eye on the stud that the nut is screwed onto if its turning then permanent damage will occur)
10-10-2008, 05:56 PM
#15
Drifting
I had (still have ) same erratic fuel gauge behaviour.
It reads about 3/4 when full. Sometimes it will flick down to empty, then up to 'correct' reading, or up to a random position in lower half of gauge. It's completely random whether it will show fuel level or empty when you start the engine!
Now it's done this since I bought the car 2 years ago.
One of first jobs I did on the car was install new sender to try to fix this. I checked the old sender and it was giving correct resistance readings (between about 0 and 75 ohms) as I moved the floating 'slider' along the pair of fine wires which run along length of sender when you dismantle it.
The 'empty' warning light has always worked fine so I was never too concerned about the gauge behaviour as I still got warning to fill up.
So I think the problem is with the 3-way connector which connects to the sender. It's on my list of thing to do this winter - I'll clean it up (contact cleaner) and if that doesn't work splice on a brand new connector. The other possibility is that the connections at the back of the gauge are dirty/corroded where they bolt onto circuit board. I have to take pod out sometime anyway to replace the blown 'D' bulb and I have new illumination bulbs to replace the fading originals.
So long way of saying the sender can be fine and you will get erratic behaviour till all contacts are clean and shiny.
It reads about 3/4 when full. Sometimes it will flick down to empty, then up to 'correct' reading, or up to a random position in lower half of gauge. It's completely random whether it will show fuel level or empty when you start the engine!
Now it's done this since I bought the car 2 years ago.
One of first jobs I did on the car was install new sender to try to fix this. I checked the old sender and it was giving correct resistance readings (between about 0 and 75 ohms) as I moved the floating 'slider' along the pair of fine wires which run along length of sender when you dismantle it.
The 'empty' warning light has always worked fine so I was never too concerned about the gauge behaviour as I still got warning to fill up.
So I think the problem is with the 3-way connector which connects to the sender. It's on my list of thing to do this winter - I'll clean it up (contact cleaner) and if that doesn't work splice on a brand new connector. The other possibility is that the connections at the back of the gauge are dirty/corroded where they bolt onto circuit board. I have to take pod out sometime anyway to replace the blown 'D' bulb and I have new illumination bulbs to replace the fading originals.
So long way of saying the sender can be fine and you will get erratic behaviour till all contacts are clean and shiny.