Fuel Gauge Help...

SprintStar · 07-30-2003, 08:10 AM

Hello All!

Any electrical gurus here?

My fuel gauge won't read to full. Is there any way I can ground the sender to check if the needle will deflect to 4/4?

I just put in a new seal and the smell of NO vapour is pure heaven... Don't wish to go thru that aveune again...

Thanks.

Sprint.

ChrisBennet · ChrisBennet's Garage

From memory, the resistance of the tank sender should measure between a few ohms (3ish?) and 73 ohms I think. I can't remember which end of the scale = full.
-Chris

david914 · 07-30-2003, 03:06 PM

Not sure how to check the guage itself, but you might want to take the sender back out (now that you've had some practice!) and clean the wires and contacts. Pretty easy to do. Once you have the sender out, bend back the retaining tabs on the metal washer, then remove the nut on the bottom. Once you have that off, carefully pull the guts out from the top of the sender. When you have it out you'll see three long wires that run from the top of the sender to the bottom. Take some very fine emery cloth and CAREFULLY clean each wire with it. Use the same emery cloth to clean the contacts on the portion that slides up and down the wires. Make sure everything is dusted off and reassemble the unit. Don't wrench down too tight on the retaining nut, just good and snug. Bend the retaining tabs back over the nut and reinstall the sending unit. If you still have a problem, check the guage (maybe someone will chime in with a good way to check it out). At the very least, your sender will be working good!

SprintStar · 07-30-2003, 05:04 PM

Thanks!!!! Will clean up my sender and post a report soon!

RoninLB · 07-30-2003, 06:21 PM

Quote:

Originally posted by SprintStar

Will clean up my sender

you may want to jump the connector black wire to the brown wire,

then turn on ignition to check the low fuel lite circuit

SprintStar · 07-30-2003, 08:34 PM

Hehe... My car is a early model.... I don't have the low fuel light ciruit. Hmmm.... I believe the senders are the same up to '89, right? Maybe I can right it up!!

RoninLB · 07-30-2003, 10:02 PM

'74 - '89 901.741.801.00 /sender
'74 - '89 477.919.133 /gasket

SprintStar · 07-31-2003, 04:32 PM

Hmm... Any other electronic gurus can offer me advice? Many thanks! My car is a '67S.

It's Friday! Here's wishing you guys a great weekend ahead!

Sprint.

blau911 · 07-31-2003, 05:12 PM

Sprint Star,
I also had problems with my 67 911 fuel gauge a few years ago. It didn't work when I first bought the car. It didn't bother me much until I ran out of fuel one evening while out on a date!
I ended up buying another one on EBay and when it arrived in the mail I pulled out my old one and replaced it. It worked fine. I decided to open up the old one to see if I could figure out how they actually work and what was broken. As David914 mentioned above, it is super easy to open it up. Just unscrew the small nut on the bottom and slide off the metal cylinder sleeve. Underneath are simply two thin gauge wires and a rubber float with metal contacts which slides up and down the wires. I saw that mine was stuck in place because one of the previous owners had used gasket glue instead of a real gasket for mounting the sending unit onto the tank. Apparently over time, the glue had fallen apart and slid down the wires onto the float itself. It had become tangled together so that the float could not go down all the way to the bottom. It had also broken one of the wires. I bought a cheap soldering gun from a hardware store, and some thin gauge wire, and soldered on a new wire. After taking the gasket glue off the float, I popped it back into the cylinder cover and put it back into the tank. It worked perfectly. After seeing how simple the unit worked, I became more dedicated to trying to fix little things on my early 911 myself.
Open yours up and see if if the float is sliding up and down properly and if the wires or contacts are unbroken. If so, then it is likely your gauge itself.
If you still think its your sending unit, I still have the extra one from my 67 that I didn't need which I will sell you for $20 + shipping.
Good Luck either way...
Blau911 (soon to be gruen911)

SprintStar · 08-03-2003, 04:51 PM

Hey Blau911!

How's the weekend?

I'm reluctant to pull out the sender again as I've just sealed it tight and no more vapor smell! Don't want to open the can of worms again, if I can help it! Hehe...

Anyway, when you took apart you sender, do you remember the connections? There are 4 connectors, right? I assume 2 are for the 2 wires you mentioned. (Which 2, by the way?) and what are the rest for? I assume one is ground? The last?

I'd like to trace the wires for myself.

Thanks and have a good week ahead!

Sprint.

Early_S_Man · 08-03-2003, 11:16 PM

Sp,

You can find a color diagram [Adobe Acrobat Reader needed] for your car at Sherwood Lee's website, here:

http://members.rennlist.org/911pcars/L59.pdf

Only three wires are used ... Brown for ground, Green for the level sender lead, and Black for the Low Fuel Warning Lamp. You can test the gauge circuit by connecting a 100 Ohm potentiometer to the green wire and ground ... sweep the pot full range, and the gauge should sweep likewise.

SprintStar · 08-04-2003, 01:17 AM

Quote:

Originally posted by Early_S_Man
Sp,

You can find a color diagram [Adobe Acrobat Reader needed] for your car at Sherwood Lee's website, here:

http://members.rennlist.org/911pcars/L59.pdf

Only three wires are used ... Brown for ground, Green for the level sender lead, and Black for the Low Fuel Warning Lamp. You can test the gauge circuit by connecting a 100 Ohm potentiometer to the green wire and ground ... sweep the pot full range, and the gauge should sweep likewise.

Thanks Early S Man!!!

I'll be sure to check out the diagram!

Hey, I'm curious.... My sender seems to have 4 connectors. But only 3 wires? I'll check to be sure. Low Fuel Warning Lamp? Hehe... I ran out of fuel last Wed and I'm pretty sure there ain't no lamp!

Mine is a '67S if it makes a difference. Hmm.... So, you mean my gauge actually needs only 2 wires to work?

Hehe... Be patient with me, ok? I'm ok with mechnical ****. But when it comes to electrical stuff, you'd better put me in an electric chair! Haha...

Sprint.