A few days ago, I asked the list for help with a gas gauge that does not register immediately on start-up and after 15 minutes or so of driving, points to full, regardless of the amount of gas in the tank. The sending unit is new. I asked for a personal intercession with the Porsche gods from anyone knowledgeable enough or with good connections for help in diagnosis. I suggested that perhaps the pod has to come out to clean the connections
to the flex strip or else the gauge itself is shot or the continuity between the gas gauge and the flex strip interface is interrupted. I have no idea whether my suppositions are correct or not. In any event, no one responded other than someone wanting to give advice about the voltage readings; slightly off the mark. Surely this query should attract a response, given the bandwidth evident on more trivial threads from time to
gpsigal - 82 with nothing special
Gerald P. Sigal" wrote:
A few days ago, I asked the list for help with a gas gauge that does not register immediately on start-up and after 15 minutes or so of driving, points to full, regardless of the amount of gas in the tank. The sending unit is new.
I was hoping someone more familiar with gas tanks and gauges would have answered your original question...
I just finished fixing a faulty gas gauge reading in my S4 last weekend. In my case, the in-tank sender unit was bad.
In your case, the problem sounds electrical. That said, I did notice something I had never heard about before while fixing my sender that may be worth looking at. The bottom of the sender unit sits in a circular container (which actually contains spiral walls within) that is fixed to the bottom of
the tank; the container is centered over the in-tank fuel filter screen. When I pulled out my sender unit, I noticed that the "lid" to this container was not attached to the side walls. My guess is that the whole contraption exists to make sure the gas is not in a turbulent state when it is pumped out
of the tank, but I do wonder if it may also play a role in an accurate reading on the fuel gauge. It may be worth verifying that all of these pieces were reinstalled properly when the sender unit was replaced.
Here is a procedure to test the fuel gauge system. I
assume no one replied
since you did not do the normal check out to help isolate the problem.
(Although I thought I sent some e-mail to someone about trouble shooting the
tank unit) Unless it is a known gremlin that has a magic fix then you
really have to start at the beginning and work backwards until you locate
A pegged gauge can generally be traced to a short in the system.
1. Locate the sending unit in the tank. It is under the carpet in the rear of the car opposite the spare. There is a black plastic cover, often under a white piece of fireproof insulating material, that can be pried up.
2. Remove the wire plug attached to the unit. If the gauge returns to empty then the problem is in the sending unit - an internal short in the wiring of the unit itself.
3. If the gauge is still pegged, then the problem is in either the wiring or the gauge.
4. Disconnect the wiring harness at the pod. This will make the gauge go to empty along with everything else.
5. Find the sending wire on the sending unit. There is a wire from the gauge and a ground. There is also a wire for the fuel light. Check the wire to the unit with an Ohm Meter. If it is a dead short to ground then there is a short in the wiring. Somewhere the wiring harness has chafed and is contacting the chassis. This may take a little driving to make the contact as the insulating is just getting worn off and may even need a little heat to make a ground contact. Remember on German cars Brown is Ground.
6. If there is no short in the wiring then the problem is with the pod. To fix this you will have to pull the pod. The most likely case will be a bad circuit board on the back of the pod or the gauge itself. The pod connections can be cleaned up with an eraser and this may be all it takes - but with an 82 I would not count on it. You can test the gauge separately by rigging up some wiring to the tank unit, but you have to be careful. If the gauge unit tests out good then the circuit board has some bad connections.
My best guess - you have some corrosion on the connection to the gauge.
DEVEK has replacement pod circuit boards - doing this is worth the effort.
I think have a gas gauge laying around some place if you need one.
Hope this helps.