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Corvette C4 Forum 1984 through 1996

Fuel gauge problem

  #1  
Old 08-25-2018, 11:16 AM
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Default Fuel gauge problem

What happen; Ran out of gas with the gauge reading one bar under 1/4 level
What I did: Made the following tests open circuit gauge reads full, install wire to short sending unit connection gauge reads one and no bar reserve light on.
Replaced sending unit with new unit, then moved arm between full up and full down before installing. Worked as expected.
Installed in tank (tank is almost empty) and started engine to get to gas station to fuel up. While idling noticed the gauge reading went to one bar below 1/4 full.
Turned of engine then turn ignition back on, but did not start engine. Gauge read one bar and reserve light on as would be expected with a nearly empty tank.
Started engine and reading went back to almost 1/4 full.
Repeated test a few more time, results were always proper one bar reading with ignition on and engine off, almost 1/4 full with engine running.
 
  #2  
Old 08-26-2018, 10:49 AM
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Welcome to the forum.
Sounds like you got it fixed or am I missing something?
 
  #3  
Old 08-26-2018, 03:56 PM
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No not fixed.
Ignition on engine OFF the gauge reads right, own bar.
Start engine the gauge goes to almost 1/4 tank which is not correct, since the tank is about as close to empty as you can get it.
The gauge is NOT reading accurately with the engine running.
A side note: the oil pressure reads about 11 PSI with ignition on with engine NOT running. I double checked that after the car was off overnight, to eliminate the possibility of residual oil pressure that might not have bleed off quickly. i.e. in the morning turned on ignition but did not start engine. That is not of big concern to me since when engine is running the pressure reading is 50-60 psi so any small error doesn't concern me, only mention because thinking it might be related.
 
  #4  
Old 08-26-2018, 03:57 PM
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That last post line two should be ONE bar not OWN bar
 
  #5  
Old 08-26-2018, 04:33 PM
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Since the oil pressure gauge is also acting squirrely, that leads me to think possibly a ground problem.
 
  #6  
Old 09-01-2018, 10:36 AM
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Not sure how a ground problem would be affected by the engine running or not running.
Maybe the issue is the fuel pump running or not running, since the pump and sending unit use the same ground.
Is there a way to get the fuel pump constantly running without the engine on?
 

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