Fuel gauge stays at half-full

[falcon]

After I gas up the fuel gauge goes to "full" and the needle heads south pretty much linearly as the gas is consumed.

I can usually drive about 350 miles before refilling. At 300 miles I noticed my fuel gauge never went below the half mark. I refilled and the same thing happens.

I read some previous posts but nothing in regards to a sticking fuel guage. Not sure how the fuel level gets to the gauge. Is it resistance from the tank somehow.

Anyone have/had a similiar problem? I sure would like to NOT have to buy another VDO gauge.

Thanks in advance.

[Rot 911]

Probably is a sticking sender. Easy to fix. Lift up trunk lid. Look at gas tank. You will see a plate with 6 or 8 small socket head bolts with a plug with wires. Remove plug. Remove socket head bolts. Remove plate and sending unit being careful to not tear gasket. Disassemble sending unit and clean out. Reinstall.

[scottb]

You must be an upbeat guy -- you said it sticks at half FULL rather than half EMPTY.

[falcon]

LOL.....I'm usually more pessimistic. I guess subconsciously (sp?) I'm trying to be more optimistic for the new year.

I'll be trying kurt V's process this weekend and will report back.

Any other ideas?

[nhromyak]

When mine did this, one of the wires inside the sender broke. I simply soldered it back up... Although it was a pain as these wires rely on tightness so the floater can easily move.

Make sure it is COMPLETELY dry before soldering....

[svandamme]

just give a good bang with your fist to the top of the sender, might just unstick it... although it'll proably get stuck again eventually

if it doesn't work , you can still fully disassemble the thing

[Kevin Taylor]

Dis-Connect the battery if you pull it out.

K.T.
1973 911 E 2.4 MFI
1983 911 SC
1965 DEVIN "D" - 1967 912 POWER-PLANT

[falcon]

Excellent tips. thanks guys

[falcon]

Just wanted to finish up and document what transpired. Possibly help other people that may have a similar issue with their gas level sender unit.

So one fine rainy day, I was in the garage and decided to remove the gas sender unit in hopes of finding out why I'm getting incorrect gas level readings. I removed 3 bolts holding down the metal cover for the connector. Removed connector , then removed remaining 2 bolts. I gripped the sender unit and pulled straight up allowing the gas to drain from the unit back into the tank.

I removed the clip from the bottom of the sender unit and removed the casing exposing the inerts. I forgot to take a pic. Its just a float that moves along 4 wire lines. This was the first time I've seen a sender unit inerts but I could not find any sticking of the float as I moved it up and down the wires. Possibly there may be a bad electrical connection or the problem could be in the wiring to the gauge or the gauge itself. It was getting late so I put the unit back together and reinstalled it into the gas tank.

I decided to bite the bullet and order a new unit from our host. Here's pics of the unit as packaged





So I'm holding the unit and notice the yellow label. It says to remove a pin before installation. I'm Looking all over for a pin that I don't know where it is nor how big. I noticed that there was a bubble under the yellow label, so I pulled it back and there it was. Here are pics.





I removed the pin and the label.

I removed the current gas level sender unit as before, then proceeded to remove the black rubber gasket. I glanced at the new gasket to be installed and it was made of cork. I wasn't too thrilled on using a cork gasket. After reviewing the black rubber material for damage, I elected to reuse the black rubber one. So I did not touch it and went ahead and installed the new sender unit.

Here's a pic of the cork gasket.



Tightened all bolts, re-attached battery and went on an errand. Fuel sender appeared to do its job at 200 miles the gauge should read just above half full.

I just realized that the original problem is that it stayed at just about half full. Which means that the problem could still exist. (I've been driving the car and this second fillup coincedently is at approximately the same mileage on the trip meter when the original problem started. The only way to make sure is to drive the car about 50 miles to make sure it drops below the half full mark, then I will know that the sender is working correctly. I'll post or edit this post to follow up on the this issue.

[Emission]

Originally posted by falcon
Just wanted to finish up and document what transpired. Possibly help other people that may have a similar issue with their gas level sender unit.

Thanks! That is a HUGE help when searching archives!

[bigchillcar]

The only way to make sure is to drive the car about 50 miles to make sure it drops below the half full mark

doncha just love it when troubeshooting means 'having to drive the p-car'..?
ryan

[svandamme]

the cork gasket does it's job very well though...i've got one , no complaints here, even re-used it when i took the sender out to clean the tank when i reinstalled it after the resto of the car...

[Jim Smolka]

Nice work.
Replacing the sensor's cork gasket is a good thing. Had a 911 where someone did not reinstall the gasket and it took a while to figure out the source of the gas smell.

And FWIW regarding the glass that contains 50% of its volume:

Optimist: 1/2 full
Pessimist: 1/2 empty
Engineer: Glass is twice as big as it needs to be.

[Roberto]

Thank you Kurt V and Randell. I have a similiar problem with my 87 Carrera coupe.

It's slightly differnt. When i fill up the guage will only register half full. And when I drive it and burn the gas it goes down pretty fast (the guage reading) so I guess that at a reading
(very new) of empty I would actually have a half of tank of fuel left. ??? But form there you just don't know when you are going to run out because the guage is reading empty.
So, thank you and I too will be doing the repair that Kurt V. recomended.

Rob

[Hendog]

OK Randall, I'm still waiting for you to come back from your 50 mile trip and report whether your gauge is reading properly. Any news?

[madmmac]

When you were driving and filling after 300 miles, how many gallons were you putting in to fill it?

[jdowty3]

I remember reading a few posts this same issue. I think the resolution was one to 2 things: a bad connection at the plug which was fixed by using contact cleaner and Q-tips or cleaning the guage unit insides for better conductivity.

[Bill in OKC]

I had a similar problem to Roberto, gauge reading half full when the tank was full. I checked the sender and it was good, then started looking at the gauge. It was a tricky problem because when I unscrewed the gas level indicator from the gauge and ohmed it out/inspected it/tested it with a variable resistor that was *close* in range to the sender - the fuel needle traveled its whole range... The problem turned out to be a small metal tab on the fuel indicator ?pod? that contacted the grounded metal gauge body when it was installed along side the oil level indicator. It created a secondary current path that robbed the needle movement of ~half the current it should have gotten. I bent that tab a bit further away from the edge and it has worked fine. Wish I had pics.

[Dan in Pasadena]

Originally posted by Bill in OKC
I had a similar problem...The problem turned out to be a small metal tab on the fuel indicator ?pod? ...Wish I had pics.

So do we!

[Roberto]

If I uderstand Bill in OKC, I need to try bending the metal tab
that is on the back of the instrument (oil and Gas) away from the gas instument connection and see what happens. I will try this after I look at the sending unit itself in the gas tank.
I will report what I find here, but don't know when I can do this.
Thanks for the info.
Rob