fuel gauge off by 1/4 of a tank!!!

[RI-Matt]

I know these cars are known for having little electrical gremlins but see if anyone can solve this one.

First, I have a VDO fuel gauge, don't know if that makes a difference but I thought I would throw that in.
When you turn the ignition on run but don't start it the fuel gage reads 1/2 a tank then I start it and the gauge says 3/4 full. I have a hot wire kit for the 340 pump in the tank, but it doesnt seem to matter in regard to fuel level.

So, where do I start?

TIA

Matt

 

[TurboDave]

Since you've stipulated that it's a VDO gauge it all makes perfect sense, although I'm surprised it isn't the other way around.

VDO gauges unfortunately are incredibly sensitive to voltage chages!!! very small voltage chages will cause their movement to be off as much as 25% of the face movement
I've got some VDO's in my 86 (and hate them), and Autometer's in my 87 (at least they are more accurate, and don't change with voltage fluctuations).

 

[RI-Matt]

Dave thanks for the reply.

Unfortunately I can't swap it for a Autometer without it looking funny ( I have the GNX style cluster)

What do you suggest I do? Can it be fixed?

Matt

 

[salvageV6]

They are supposed to be a bridge circuit and immune to voltage changes, at least the stocker is.

I would email VDO or call them and see if it's a known problem or try to get some tech. support.

May be defective.

 

[TurboDave]

Originally posted by salvageV6
They are supposed to be a bridge circuit and immune to voltage changes, at least the stocker is.

I would email VDO or call them and see if it's a known problem or try to get some tech. support.

May be defective.

That may be what's "advertised" but in real life, it's not often that way.

 

[atl gn]

Are you still using the factory sending unit? I know that all the digital dashes that I have had only tell the truth when the key is on, but when you crank the motor it lies by about 3 or 4 gallons. I think thats the way pretty much all these cars are, I think ive just gotten used to it

 

[salvageV6]

Mine is accurate, however the tank hasn't been messed with much in it's life.

I think people do more damage to these things than the factory design is flawed.

As to VDO's innards I dunno but it should be a bridge circuit too.

 

[terryk]

Wow, I've finally figured out that my digital dash fuel gauge actually reads fuel used and not fuel remaining. Once I got past that I'm really happy with it. I run out when it says 16 gals. Perfect.

Ok, I really run out when it says 6 gallons. The gauge is right, the sender is goofy.