OK...I searched this question and I sure I missed it so will ask here... sorry if its a repeat


My (89 couple) XJS has a very annoying gas gauge. It reads about 1/4 tank almost all the time. When you fill it up it stays there but as you drive and it warms up it rises to about 1/2 tank. See'n that you get 6-10 MPG in these cars I am hoping I can figure out a way to correct it with out major dashboard removal surgery! I have replaced the fuel sending unit in the trunk and still same thing / readings. Do you think its a mechanical problem with the level of gas and its ability to read it or an annoying relay issue somewhere along the line from dash gauge to tank? My brother in law in SC who is driving it for me and keeping her up and running as opposed to sitting did run out of gas one time and that's what made us realize it didn't work lol but he cant remember if the yellow light came on. I think so but cant be 100% sure


Is there a "oh check this simple thing first" type of fix I should know or try?


Thanks!!!!

 

Gauge problems are common on these cars.

Usually removing the cluster (not hard to do) and gently cleaning all the contact points on the printed circuit....and adding an extra ground wire....puts things back in order.

But first.....

Remove the sending wire from the sending unit (can't remember the color offhand...someone will chime in) and, with the key 'on', touch the wire to ground. The gauge should rise right to the top. If it doesn't, the gauge is faulty, or you have a bad contact.

Cheers
DD

 

Excellent information


I will see what I can do with that information....really appreciate it


I have heard taking the dash apart as they get old and brittle can lead to major headaches....true? tips?

 

Yeah, old stuff breaks at times, by you're not really "taking the dash apart". Just pulling the cluster out.

It's been a few years for me so others might fill in some missing details....

-Next to the cluster lens are two pieces of plastic trim with a center joiner piece. Remove three (?) screws to remove this trim.

-In each upper corner of the cluster are two plastic covers that pop out to reveal two screws. Remove the screws. At this point I recall that the cluster can be wriggled outward...but there might be two screws in the bottom corners as well.

-Tricky part: reach behind the cluster to release the two wiring harness bundles. Each has a 'trigger' that needs to be pressed/squeezed to disengage the connector from the cluster

-Have steering wheel fully outward for easier removal of cluster. Or, remove the steering wheel

-On removal and reinstallation be careful to avoid snagging the printed circuit on sharp edges/object

Cheers
DD

 

Probably a high resistant short at the plug. Clean printed circuit plug with contact cleaner or a pencil eraser. FYI and you don't need it, The printed circuit can be soldered . scrape down to copper trace and use a light iron