TheSamba.com Forums
 
  View original topic: fuel gauge not working - ground for sending unit Page: 1, 2  Next
t-royR Sat Oct 22, 2016 8:59 am

trying to get my fuel gauge to work. manual indicates that when installing the fuel sending unit (may have that term wrong) - the part that installs into the tank, that there should be a ground connection between the rubber gasket and the tank. I don't see that ground on mine. I see the little gap in the gasket where the ground contact should be, but don't see any metal on the unit that would ground. do i add something to make the ground?

Bobnotch Sat Oct 22, 2016 11:16 am

t-royR wrote: trying to get my fuel gauge to work. manual indicates that when installing the fuel sending unit (may have that term wrong) - the part that installs into the tank, that there should be a ground connection between the rubber gasket and the tank. I don't see that ground on mine. I see the little gap in the gasket where the ground contact should be, but don't see any metal on the unit that would ground. do i add something to make the ground?

No. The screws should ground the sending unit. It's possible that you might have too much paint under the tank anchor clips, which is not making a good ground.

MonT3 Sat Oct 22, 2016 11:22 am

t-royR, the unit may be dirty and need a good cleaning. Mine did the same thing and I thought the grounding was causing the issue. I built a small ground wire and tried that without any success. I tried to ground from the body to one of the screws holding the unit in place. No success. I ended up pulling the unit out, taking it apart very carefully as there are two filament wired inside the tube. There was a bunch of fine rust particles all over. I have a ultrasonic cleaner and so it along with a spare I had tried with the same results took a 30min bath in cleaner and once done I put it back together, slipped it in an just wired the brown wired to the terminal on the top of the unit. Turned the key and it came back to life and has been working since. Here’s what the unit looks like inside the tube…


The cleaner I used was Simple Green. I think a good soaking and cleaning with careful attention being given to the wires so as not to break or disrupt the connections to the float would help. Hope the info helps some.

t-royR Mon Oct 24, 2016 9:43 am

Thanks. I'll give it a try. gives me a reason to buy an ultra-sonic cleaner, which is something I've wanted.

Any advise on what kind to purchase? Better yet, what to stay away from?

T-roy

sjbartnik Mon Oct 24, 2016 1:20 pm

Sending unit grounds to tank through the mounting screws, tank grounds to body via its mounting screws/plates. Gotta have a good electrical connection at both points.

t-royR Mon Oct 24, 2016 1:24 pm

Thanks for the confirmation on that. Makes me wonder why the manual makes a point of stating the need for that ground beneath the rubber gasket. In fact, the manual makes two references to the importance of that.

T-roy

KTPhil Mon Oct 24, 2016 1:51 pm

MonT3 wrote:

Man, are those sender tops really that distorted, or was it the camera lens?

supersuk Mon Oct 24, 2016 4:51 pm

My sender top is that distorted too. I asked if that was normal and no one replied. Guess its not supposed to be like that!

KTPhil Mon Oct 24, 2016 11:39 pm

supersuk wrote: My sender top is that distorted too. I asked if that was normal and no one replied. Guess its not supposed to be like that!

I am surprised you ca get it to seal to the tank like that. I wonder how it got that way? The tank flange is flat, right? Trying to bend it back flat would almost certainly crack it.

ataraxia Tue Oct 25, 2016 5:40 am

I ran a separate ground from one of the mounting bolts on the sender to a ground on the body - my gas tank was powder coated and I wasn't about to chip away at it to improve the ground. Took 5 minutes to run a new wire.

The only warped one I had like that was wavy and had a shitty rubber gasket (which will fall apart) and it was torqued on better than anything else on the car.

supersuk Tue Oct 25, 2016 10:45 am

I had that crappy rubber gasket on mine too when I took it off. I replaced it with a blue rubberish gasket that had the VW logo on it. Mine was also torqued on so tight that I broke my 1/4" ratchet. Had to use a 3/8" to take it off. Surprised that the bolt didn't break. PO must've torqued it down to prevent the gas smell?


KTPhil Tue Oct 25, 2016 11:07 am

You might try using a vice to flatten the flange. That is less likely to crack it than pliers or a hammer. Or maybe use some sort of large pipe fitting to put pressure all around the circle when you clamp it in the vice... get creative!

Weird that it bent like that... must have been overtorqued big time. That gasket is submerged when the tank is full so a good seal is mandatory.

ataraxia Tue Oct 25, 2016 11:28 am

KTPhil wrote: That gasket is submerged when the tank is full so a good seal is mandatory.
If the gasket is submerged when the tank is full - you're in deep shit because the gasket is on the OUTSIDE of the tank...

Torquing the shit out of these little bolts doesn't eliminate the gas odor - replacing the gasket does...over-tightening the bolts will just make it worse. The gasket is cheaper than the sender...especially now that good OE units are NLA.

KTPhil Tue Oct 25, 2016 11:34 am

By submerged I mean the fuel level is at or above the seal level, so any gap will leak instantly. This is unlike a gas cap that is above the level unless you are cornering hard over uneven terrain, and is not quite as critical. A gas cap will not leak just sitting parked; a leaky sender seal will make a puddle on top of the tank.

ataraxia Tue Oct 25, 2016 11:37 am

KTPhil wrote: By submerged I mean the fuel level is at or above the seal level, so any gap will leak instantly. This is unlike a gas cap that is above the level unless you are cornering hard over uneven terrain, and is not quite as critical. A gas cap will not leak just sitting parked; a leaky sender seal will make a puddle on top of the tank.

I've never had that happen but I also don't think I've ever filled the tank that full.

Donnie strickland Tue Oct 25, 2016 11:57 am

ataraxia wrote: KTPhil wrote: That gasket is submerged when the tank is full so a good seal is mandatory.
If the gasket is submerged when the tank is full - you're in deep shit because the gasket is on the OUTSIDE of the tank...

Torquing the shit out of these little bolts doesn't eliminate the gas odor - replacing the gasket does...over-tightening the bolts will just make it worse. The gasket is cheaper than the sender...especially now that good OE units are NLA.
VDO sells new Brazilian sending units. I don't have any personal experience with them.

KTPhil Tue Oct 25, 2016 12:51 pm

ataraxia wrote: KTPhil wrote: By submerged I mean the fuel level is at or above the seal level, so any gap will leak instantly. This is unlike a gas cap that is above the level unless you are cornering hard over uneven terrain, and is not quite as critical. A gas cap will not leak just sitting parked; a leaky sender seal will make a puddle on top of the tank.

I've never had that happen but I also don't think I've ever filled the tank that full.

If you fill it to the bottom of the neck where it meets the tank, it will have gas at or above the sender gasket. The sender flange sits in a little depression in the top of the tank.
(Click to enlarge the drawing)


ataraxia Tue Oct 25, 2016 1:21 pm

Donnie strickland wrote: ataraxia wrote: KTPhil wrote: That gasket is submerged when the tank is full so a good seal is mandatory.
If the gasket is submerged when the tank is full - you're in deep shit because the gasket is on the OUTSIDE of the tank...

Torquing the shit out of these little bolts doesn't eliminate the gas odor - replacing the gasket does...over-tightening the bolts will just make it worse. The gasket is cheaper than the sender...especially now that good OE units are NLA.
VDO sells new Brazilian sending units. I don't have any personal experience with them.

I'm aware of this...but they're still more expensive than the gasket.

I have NOS German/Czech units so it's unlikely that I'll be buying a Brazilian one any time soon.

ataraxia Tue Oct 25, 2016 1:22 pm

KTPhil wrote: If you fill it to the bottom of the neck where it meets the tank, it will have gas at or above the sender gasket. The sender flange sits in a little depression in the top of the tank.

The geometry makes sense but I just don't put that much fuel in my car. Even when I was driving long distances in it I didn't fill it up that much.

EasternNotch Tue Oct 25, 2016 3:40 pm

ataraxia wrote: I ran a separate ground from one of the mounting bolts on the sender to a ground on the body - my gas tank was powder coated and I wasn't about to chip away at it to improve the ground. Took 5 minutes to run a new wire.


I had to do the same thing with mine a couple years ago when I 'restored' the tank. got it all back together then realized the paint was preventing ground. I snuck a ground wire off the sending unit to the body and shazam problem solved and no messing with my freshly painted tank



Powered by phpBB © 2001, 2005 phpBB Group