87 Fuel Gauge Read-Out
Thread Starter
Racer
Joined: Nov 2002
Posts: 303
Likes: 0
From: Miami FL
87 Fuel Gauge Read-Out
Need someone's help. I purchased an 87 and runs great but the fuel gauge in the instrument cluster marks full all the time. The person I purchased it from advised that it had a new full pump. Now here is the weird part. A problem like this one would think the sending unit is messed up but when you first turn on the car it reads the actual amount of gas in the tank. When you start the drive it then begins to fill up until it eventually shows as if its full. Now, shut the car down and wait a few hours and when it turns on again it show again the correct amount for a while until it is driven again. Could the previous owner possibly messed up the sending unit or put a wire in the wrong place? How hard is it to check the tank or the connections? :confused:
[Modified by My87, 3:50 AM 12/10/2002]
[Modified by My87, 3:50 AM 12/10/2002]
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Well.... there should be a single pink wire coming from the sending unit inside of the tank. This is a variable ground that gets sent to the dash if I am remembering right. It is possible that they messed something up when installing the pump, but i would hope not as it is rather straightforward. :)
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: 87 Fuel Gauge Read-Out (My87)
Sounds like you have a problem in the cluster. The gas tank level sender is a variable resistor and the cluster circuit essentially reads the value and indicates the fuel level. The sender can't reset itself everytime you turn the car off, but the cluster circuit can.
Thread Starter
Racer
Joined: Nov 2002
Posts: 303
Likes: 0
From: Miami FL
Re: 87 Fuel Gauge Read-Out (My87)
Ok, I understand about the cluster but won't it just show full as soon as I run the car? Instead what it does is, it starts gradually increasing to the full level. Lets say I start at half a tank, it will go up one line within a mile or so, then one or two more lines a few more miles and so on until it show full again. Is that still a sign of a bad cluster? Or a negative cable not installed correctly in the tank?
:confused:
:confused:
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: 87 Fuel Gauge Read-Out (My87)
The cluster is essentially a digital voltmeter and it can drift with temperature (normally too small to cause a reading change) when it is defective. Turn the car off and the circuit cools down. Turn the car on and it goes through the same warm up cycle again. The gas gauge sender is a float operated variable resistor whose temperature is the same as the gas in the gas tank which is very stable. A bad connection at the sender will not start out good and slowly get worse every time you turn the car on. A bad connection will always be bad or it will be intermittent.
It may be beneficial to unplug the cluster and replug the connector to clean the contacts. If it still does it, my vote is on the circuit on the cluster circuit board.
It may be beneficial to unplug the cluster and replug the connector to clean the contacts. If it still does it, my vote is on the circuit on the cluster circuit board.
