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txasylum
Samba Member
Joined: December 15, 2004
Posts: 389
Location: Boyers, PA
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 Posted: Sun Nov 24, 2019 3:56 pm Post subject: Fuel sending unit / fuel gauge question |
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Car is 74 super beetle
Should there be continuity between the two wires that connect to the fuel sending unit? I've been chasing my fuel gauge problem (not reading full when full, but read less than 1/2 tank). I've taken the fuel sending unit out and checked the full/empty ohm reading. That is good. I connect the wires when fuel sending unit is out of the tank. I can get it to read full or empty depending where I place the lever.
I've been bending the wires trying to get it to read. I got it to read empty when empty, but when I put 5 gallons in the tank, it read just above 1/4. So I played with bending the wires so that it reads closer to 1/2 tank, but then when I emptied the fuel tank the gauge reads about 1/4.
I checked continuity between the two wires and I get continuity (buzzes on my meter). If one is a ground and the other is 12v, why am I getting continuity? |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51153
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Sun Nov 24, 2019 5:08 pm Post subject: Re: Fuel sending unit / fuel gauge question |
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The continuity between the terminals changes as the fuel level rises or falls, one is a ground (on the side), the other is the variable ground to the gauge (near the middle with plastic surrounding it). You should get 0 ohms between the brown wire and the car's body, and ~70-90 ohms between the 2 terminals on the sender (wires disconnected) at empty, close to 0 ohms at full.
How sure are you the float actually floats well in gasoline?, many replacement units don't after soaking for a year or so.
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txasylum
Samba Member
Joined: December 15, 2004
Posts: 389
Location: Boyers, PA
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| Posted: Sun Nov 24, 2019 5:13 pm Post subject: Re: Fuel sending unit / fuel gauge question |
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I took it out of the gas tank and connected it to the wires. By hand, if the one lever is in the down position, the fuel gauge shows empty. If the lever is in the upper most position, fuel gauge shows full. I just can't get it to do that when it is in the fuel tank.
I've considered buying a new one, but it seems all the tests I do this sending unit is good, but who knows. It just is not working properly in the fuel tank.
From what I read online, one position is 11 ohms and the other is 73 ohms, which is what this gauge reads.
| busdaddy wrote: |
The continuity between the terminals changes as the fuel level rises or falls, one is a ground (on the side), the other is the variable ground to the gauge (near the middle with plastic surrounding it). You should get 0 ohms between the brown wire and the car's body, and ~70-90 ohms between the 2 terminals on the sender (wires disconnected) at empty, close to 0 ohms at full.
How sure are you the float actually floats well in gasoline?, many replacement units don't after soaking for a year or so. |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51153
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Sun Nov 24, 2019 5:23 pm Post subject: Re: Fuel sending unit / fuel gauge question |
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Sounds like the float isn't floating, or the arms are hanging up on a baffle inside the tank. 
_________________
Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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txasylum
Samba Member
Joined: December 15, 2004
Posts: 389
Location: Boyers, PA
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| Posted: Sun Nov 24, 2019 7:13 pm Post subject: Re: Fuel sending unit / fuel gauge question |
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I've got the tank out of the car and have been messing with this sending unit. I got it to register on empty, but it seems that the long arm with the float hits the top of the tank, therefore it is not raising the smaller float up high enough to register full. If I bend the arms so that it pushes the smaller float up to register full, then it is too high up when it should be registering the tank empty, therefore it shows 1/4 or so full when in fact it is empty.
I thought about ordering a new one, but it seems I'll have the same problem. IDK
| busdaddy wrote: |
| Sounds like the float isn't floating, or the arms are hanging up on a baffle inside the tank. |
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beetlenut
Samba Member
Joined: May 27, 2009
Posts: 2983
Location: RI
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| Posted: Sun Nov 24, 2019 8:04 pm Post subject: Re: Fuel sending unit / fuel gauge question |
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[quote="txasylum"]I thought about ordering a new one, but it seems I'll have the same problem. IDK
FWIW, I put a new one in my 74 Super this last year and it doesn't work that much better! I assume you also tried switching the wires around going to the sender. I also assume you put the sender into the tank clocked the correct way.
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scrapyards are for quitters
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| Wetstuff wrote: |
| ... I spend more time shaking it than directing it?! I get a pretty decent blast for 8sec. then have to shake it again. |
- Words to live by right there!
My 74 Super rebuild thread: http://www.thesamba.com/vw/forum/viewtopic.php?p=6507104#6507104 |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51153
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Sun Nov 24, 2019 8:27 pm Post subject: Re: Fuel sending unit / fuel gauge question |
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| txasylum wrote: |
| busdaddy wrote: |
| Sounds like the float isn't floating, or the arms are hanging up on a baffle inside the tank. |
I've got the tank out of the car and have been messing with this sending unit. I got it to register on empty, but it seems that the long arm with the float hits the top of the tank, therefore it is not raising the smaller float up high enough to register full. If I bend the arms so that it pushes the smaller float up to register full, then it is too high up when it should be registering the tank empty, therefore it shows 1/4 or so full when in fact it is empty.
I thought about ordering a new one, but it seems I'll have the same problem. IDK
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Ummm....., the smaller float comes free of the long arm and continues rising for the top 1/2 of the tank, the longer one only deals with 1/2 tank or less.
_________________
Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
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Dan the workingstiff
Samba Member
Joined: July 03, 2006
Posts: 824
Location: Downriver, MI
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| Posted: Mon Nov 25, 2019 12:53 am Post subject: Re: Fuel sending unit / fuel gauge question |
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[quote="beetlenut"]
| txasylum wrote: |
I thought about ordering a new one, but it seems I'll have the same problem. IDK
FWIW, I put a new one in my 74 Super this last year and it doesn't work that much better! I assume you also tried switching the wires around going to the sender. I also assume you put the sender into the tank clocked the correct way. |
I'm jumping in with NO EXPERIENCE on this issue. But, if it needs to be referenced front to back or back to front due to the amount of fuel and where it's sitting. |
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txasylum
Samba Member
Joined: December 15, 2004
Posts: 389
Location: Boyers, PA
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| Posted: Mon Nov 25, 2019 5:18 am Post subject: Re: Fuel sending unit / fuel gauge question |
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Yes, all is in correct and plugged in correctly. I verified ground to ground, etc.
Well, I just ordered a new one. Let's see what happens Monday when it comes in.
[quote="beetlenut"]
| txasylum wrote: |
I thought about ordering a new one, but it seems I'll have the same problem. IDK
FWIW, I put a new one in my 74 Super this last year and it doesn't work that much better! I assume you also tried switching the wires around going to the sender. I also assume you put the sender into the tank clocked the correct way. |
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AlmostHeavenWV_VW 
Samba Member
Joined: October 12, 2017
Posts: 1966
Location: WV
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| Posted: Mon Nov 25, 2019 8:44 am Post subject: Re: Fuel sending unit / fuel gauge question |
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Not my work, but I would advise reading up on this member's (blue69baja)work and watch his videos on the fuel sender function, available aftermarket sender brands, and ways to adjust for better performance:
https://www.thesamba.com/vw/forum/viewtopic.php?t=725590&highlight=fuel+gauge
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1973 Standard Beetle
1600DP AK case
Solex 34PICT3 Carb
Bosch DVDA 205AJ Distributor |
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VW_Jimbo
Samba Member
Joined: May 22, 2016
Posts: 9967
Location: Huntington Beach, CA
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| Posted: Mon Nov 25, 2019 8:45 am Post subject: Re: Fuel sending unit / fuel gauge question |
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The new fuel level sending units suck!
Here is a great article on the subject!
https://www.thesamba.com/vw/forum/viewtopic.php?t=711130
_________________
Jimbo
There is never enough time to do it right the first time, but all the time necessary the second time!
| TDCTDI wrote: |
| Basically, a whole bunch of fuckery to achieve a look. |
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GFY's Xevin and VW_Jimbo!  |
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Blue69Baja
Samba Member
Joined: September 04, 2008
Posts: 1065
Location: Fair Oaks
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| Posted: Tue Nov 26, 2019 7:53 am Post subject: Re: Fuel sending unit / fuel gauge question |
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69-79 fuel gauge system, Super and Std videos by me. Should provide a full understanding of the system and the problems introduced by non OEM parts.
Pretty sad but workable.
The videos are not professional but hopefully will answer your questions.
https://www.youtube.com/channel/UC_2W_OgL6dEgsA5VVBrKObA/videos?view_as=subscriber
Jim
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69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original.. |
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