I have successfully fixed my slow fuel Gauge on my 1993 LS400. I believe that this fix applies to 1993 and 1994 LS400. I ordered the capacitors from digikey.com. I have attached a copy of my digikey invoice for your reference.
The DigiKey part numbers I ordered were:
399-3634-ND to replace C142
CAPACITOR TANT 4.7UF 25V 10% RAD
399-3527-ND to replace C147
CAPACITOR TANT .10UF 50V 10% RAD
I only needed to remove the first circuit board (smaller one) and flip it down. These two capacitors are NOT soldered through the board (surface mount) so you do NOT need to remove the larger board at all.
I filed my soldering iron to a fine point. I used a stiff pointed screw driver to push on the old capacitor while applying heat. That helped remove it from the circuit board. I then clipped and bent the new capacitor terminals at an angle evenly on each side. My circuit board was printed with a negative "-" symbol for each capacitor. The capacitors are printed with a positive "+" on one side. So I soldered accordingly. I dipped the iron in solder paste flux and added a small amount of additional solder to the tip of the iron before I re-attached the new caps.
My fuel gauge now pops right up as soon as I turn the ignition key. It was 9 degrees outside at the time, and previously that would have never happened.
Attached is a pic from Jim Walker that I used to locate C142 and C147 on the larger main board.
Sorry to bring up an old thread but I have been searching everywhere for a writeup like this for SC300/400's and have found nothing. This is the first constructive, step-by-step writeup I've found for fixing LS400 fuel gauges. I am experiencing the same slow/inaccurate fuel gauge issue in my 1993 SC300. Is there any similarity in the circuitry between the SC and LS clusters so that the same fix might be applied to both cars?
Just want to say thanks for the extreme good and detailed explanation.
Easy to source parts and easy to install.Took me 75min from start to end ( I am not a mechanic ) and now the meter function perfectly.