Faulty Fuel Gauge / fuel float in a '69 1750 coupe ? !

[Ash Gordon]

The needle in fuel gauge is constantly waving / moving and it is hard to work out how much fuel is actually in the tank.

It is only steady when the car is not moving, but I am never sure I can trust where it stops.
So far I haven't run out of fuel but would obviously prefer to fix the issue rather than put up with it.

Has anyone had similar problems or knows how to fix the problem?

Thanks Ash

[Stephen Aarons]

This seems like a common thing among older Alfa's, mine does it, and so does my brothers cars. Its almost like a game haha, see how high or low u can get it goin around a corner 

[alfagtv100 (Biggus)]

My 1750 GTV also features this endearing 'characteristic'.  I have resorted to using the trip meter as a guide.
At 140 miles of normal driving, I have already thought about where the next petrol station might be.  On the highway, its at 180-200 miles.  Track days are harder, so I wait until the red light has started to flicker.  If it stays on, I start to sweat.  I am unsure if my target miles are conservative but I don't run out of fuel.
This strategy also helps avoid picking up the rubbish that sits at the bottom of the tank.
I find this the 'cheapest' method of dealing with the problem.

Cheers,

Marco

[Gary Pearce]

There is an easy fix to the wavering needle. You may have noticed that 2000 GTV's don't do it.
It is just a matter of fitting a resistor (choke) across the fuel gauge in the dash. This produces a permanent current when the key is on that centres the gauge needle, which then uses the float in the tank to vary the gauge position, but taking a few seconds to do so. a few. Thus the stable needle.
It takes a bit of experimentation to get the right resistor. If I can find the article that was published in our club magazine a few years ago, I will post the link on this site.

[Fast Eddie]

Interested to see the mechanics of this fix Gary as i have the problemin my 116 GTV too.

[Ash Gordon]

Thanks for the feedback, starting to realise the old car has many "endearing qualities", many of which I would ideally like to iron out, without sacrificing the 105 charm.

Looking fwd to the post / link from Gary and fixing the problem.

In reading Gary's post it's is still the amount the float moves that shifts the needle and the resistor just "dulls / slows" the movement.  So should the float & hence the needle be moving so much?  Or is it as everyone keeps saying another quirk of the older Alfas ...

Is there a spring or the like that stiffens up the float mechanism, that might have broken or worn that would stop the rapid movement??    Just guessing here but they were my initial thoughts.

[adriank]

I also have this issue, if it's as simple as getting the right resistor and soldering it in place i would be very interested to try it. It's really so when people (other than myself) are in the car don't freak when the red light flickers...

I would be hesitant to pull out the sender unit and start playing with the mechanism - you will most probabaly find no spring on the sender anyway.

Adrian.

[Gary Pearce]

Yes you are right Ash. The mod just slows up the movement only. Seems pretty good though. There is no alteration to the float system and I don't think a spring of any kind would work.
I still can't find the write up, but I have also experimented reasonably well with connecting a low wattage globe across the back of the fuel gauge. Takes a bit of experimentation to get it right and there is a dull glimmer from the globe that may not suit everyone, so the resistor (and the diode) is the solution I believe.

[Colin Byrne]

I've pulled a lot of these senders apart and there is no spring, its just a pivoting arm, I don't think a spring would be the answer anyway as your looking for a some damping in the movement

[Ash Gordon]

Not having pulled the sender out as yet, I am surprised that it's just a free floating arm with no counter resistance. 

Thought there may originally been have been a retardant of some kind to slow the rapid rise and fall.

Perhaps adding a small amount of weight to the end of the arm of the sender might work??   

Then again adding a resistor at the back of the gauge sounds a whole lot easier !

[adriank]

Gary, i remebered the idea of a resistor for my fuel gauge the other day - did you have any luck finding the article regarding what sort of resistor and where to put it?

Adrian

[Davidm1600]

Me too !!  It really is a 1750 GTV problem, the fuel gauge, since mine too also has an endearing quality.  Mine though is a little different in as much as when the tank is full it only ever at best reads 1/2 full. So it becomes a bit of guessing game as to when it is really empty.  I think the red warning light does work but as my trip meter doesn't work I generally work on the theory that when the guage reads empty, I have roughly 1/2 a tank.  So far in 12 years ownership I havn't ever run out of fuel, but possibly more by good luck than anything else. 

I would be interested if anyone has any ideas why my gauge never registers as full.   Dave

[Gary Pearce]

Yes sorry Adrian.
I can't find that article, I was sure it was in Cross & Serpent a few years back.
Here is what I did initially to fix the problem in my Giulia Sprint GT.
I used a simple dash light globe (about a 4 or 6 watt 12v globe) and soldered two wires onto the globe to afix across the tank unit wire on the back of the instrument. It took a bit of experimentation with different wattage globes. With the next car I went to a techno-wiz (Jaycar I think) to give me a resistor to match what I wanted. It is too hard now for me to pull the gauges out of my race car due to the cage so I can't help you much more than that right now.

[Gary Pearce]

Part two to this is real easy to fix. Fuel gauge and warning light acuracy.
1) Just unscrew the tank unit from the top of the tank in the boot. 6 screws. You might need to disconnect the fuel pipe and the two wires before lifting out the tank unit. 5 mins. so far.
2) Now connect up the two wires again, also connect a tempoary earth wire between the (now removed) tank unit and a suitable clean earth connection. (maybe the boot latch)
3) Turn the key on.
4) While holding the tank unit in your hand, you can watch the dash gauge through the back window, you can move the float leven through it's travel and see the appropriate movement on your dash gauge. A bit easier to do with two people, but I like to do it myself so I can see exactly where it is reading. 10 mins now.
5) Stick a measuring stick in the tank through the fuel gauge hole and measure the level of fuel remaining. Draw a conclusion on how much fuel you have (say 1/2 tank)
6) Measure the travel of the float on the gauge unit, noting when the light comes on.
7) Vevy gently bend the wire arm holding the float to match what fuel level you have, and where you would like the fuel light to come on. 15 minuites all up.
A couple of trials are usually required to get what you desire, but I haven't had much trouble geting an accurate gauge this way, with a light that comes on at about 8-10 litres to go.
Some care issues.
Make sure your fuel tank is securely earthed to the body with clean shiney screws or you will get voltage drop and the gauge will be inaccurate.
Make sure the plastic float is air tight. (shake it, or push it in a glass of water to see if any bubbles can be squeezed out)
There is no safety risk in doing this opperation providing you are doing it on a cool day. It is pretty hard to ignight fuel with a spark, as it is FUEL VAPOUR that is dangerous, but just be causious with ventilation and securing earth connections befor turning on the key.
All up 30 minuites and you should have a more accurate 105 fuel reading.

[Brad M]

Nice little tip there Gary. Cheers