speratic functioning of fuel gauge - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• speratic functioning of fuel gauge by evangelos on 18 Sep, 2007 08:51
• hi all,
  
  my fuel gauge has been going crazy.
  
  
  my car runs on a 2 tank veggie conversion and i dont use a lot of diese so my fuel gauge should move very little. i usually get between 4k-5k  of km per diesel fillup.
  
  it can't be a fuel selector valve because i have a clear filter before the IP and the veggie color is golden brown and clear on diesel mode.
  
  i did notice a few time when the rpm was dropping the guage would move towards the empty but as i revved the motor it would move towards the Full mark.  but this only happened once in the past 3 weeks.
  
  is this a CLEAR sign of the alternator going or are there other signs??
  
  i dont just want to change the alternator for nothing - naturally.
  
  thanks
• #1 by Vincent Waldon on 18 Sep, 2007 16:06
• Has the temp gauge started to be a bit wonky as well ??   Next time you can make the fuel gauge move by revving the car see if the temp gauge moves as well.
  
  If so, chances are the issue is the voltage regulator mounted on the cluster that is shared by both gauges.
  
  If not, I'd be inclined to use a voltmeter and see what is happening to the system voltage as you rev... this would sort out an alternator issue quickly.
• #2 by evangelos on 19 Sep, 2007 21:01
• hi vince,
  
  thanks for the direction.
  
  no the temp guage is a contant, does not move past 90C.
  
  the fuel guage was doing the same thing to day.
  
  i checked the battery and its at 14.37v but that was at idle
  
  but
  
  if its not dancing around when the mechanic is looking at the alternator as i rev it  will look normal so i guess i should be hope it acts wacky but as usuall it probably wont.
  
  it keep you all readers informed
  
  evan
• #3 by Vincent Waldon on 19 Sep, 2007 21:19
• Bonjour Evangelos....
  
  Well if your dash regulator seems OK (temp gauge not impacted) then I think you're on the right track... see if the alternator voltage varies with speed.
  
  If not, next step might be to pull the fuel tank sender and see if it moves freely.
  
  
  Vince
• #4 by evangelos on 19 Sep, 2007 23:45
• i forgot to mention that my speedometer also works whenever it wants as well. are these 2 problems connected?  i cant remember if they both started malfunctioning at the same time or not
• #5 by bigJ on 31 Dec, 2007 01:26
• This reply is probably a bit late but my fuel gauge did the same thing. I too run wvo duel tank but when I switch I get a little cross contamination.  One day I topped of the diesel tank and after that my gauge sporadically. The veg. ended up coating the contact on the sensor and after a good cleaning works again.
• #6 by vanagonturbo on 31 Dec, 2007 02:02
• It is possible that they are related. Those instrument clusters are known for failure on a regular basis.
  
  Now that said, I would listen to Bigj, running a two tank system can create extra problems with fuel gauge readings and the like. Start with what has been changed and go backwards.
  
  HTH
• #7 by evangelos on 31 Dec, 2007 02:36
• my problem seems to have gone away and i have a feeling it might be due to cross contamination with the veggie.  now that it is colder here i drive an extra 2 minutes after i purge to make sure all veggie is cleared. i also dont wait for the diesel fuel to reach 1/4 tank.
  
  thanks for all the input guys
  
  evan