Fuel Gauge / Fuel Sending Unit
11-09-2005, 03:31 PM
#1
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Fuel Gauge / Fuel Sending Unit
Hello everybody,
I would like to introduce myself. My name is Bernd, 42 years old, from GERMany. I'm a proud owner of a C2 '66 Convertible 327 in pearl-silver ... well --- I'm married too ... have a dog, mongolian mice and some salt water fish ... livin tho' ...
...
Well ... NOW --- I would LOVE to come up with my question ... now that all of you got to know me a little bit ...
How am I gonna start ...?!?
My problem is: I have a new fuel sending unit (0-90 ohm) including a new fuel gauge (bought these items new to solve my problem) but ... no kidding ... the problem is still there. Seems to be a problem within the wiring system.
All measurements = ignition on.
Facts: Three cables come through the fuel sending unit. One is +12 volt (comes with ignition). On round connector one. The second cable goes to the fuel gauge on round conntector two. The third cable is ground connector with body.
On the fuel gauge we have three connectors. On one connector we have +12 volt (comes with ignition). The second connector is the return wire from the fuel sending unit (round connector two). The third connector is ground.
If this should be wrong PLEASE be so kind to inform about the right situation. Maybe somebody has a wiring diagram ... ?
If the tank is empty there is O ohm between the two connectors of the fuel sending unit which is correct. The fuel gauge shows empty. So far so good.
If the tank is full there is 90 ohm between the two connectors of the fuel sending unit which is also correct. Normally the fuel gauge would have to show full but it doesn't ... it only shows 1/4.
When I put a bridge between ground & the return wire on the fuel gauge it shows full but the wire becomes hot.
When I disconnect the two cables of the fuel sending unit the fuel gauge shows 1/2.
Where is the mistake? Is anybody having an idea how to solve my problem? I would really appreciate a solution ...
Looking forward to receiving some lines.
Take care,
Bernd
I would like to introduce myself. My name is Bernd, 42 years old, from GERMany. I'm a proud owner of a C2 '66 Convertible 327 in pearl-silver ... well --- I'm married too ... have a dog, mongolian mice and some salt water fish ... livin tho' ...
... Well ... NOW --- I would LOVE to come up with my question ... now that all of you got to know me a little bit ...
How am I gonna start ...?!?My problem is: I have a new fuel sending unit (0-90 ohm) including a new fuel gauge (bought these items new to solve my problem) but ... no kidding ... the problem is still there. Seems to be a problem within the wiring system.
All measurements = ignition on.
Facts: Three cables come through the fuel sending unit. One is +12 volt (comes with ignition). On round connector one. The second cable goes to the fuel gauge on round conntector two. The third cable is ground connector with body.
On the fuel gauge we have three connectors. On one connector we have +12 volt (comes with ignition). The second connector is the return wire from the fuel sending unit (round connector two). The third connector is ground.
If this should be wrong PLEASE be so kind to inform about the right situation. Maybe somebody has a wiring diagram ... ?
If the tank is empty there is O ohm between the two connectors of the fuel sending unit which is correct. The fuel gauge shows empty. So far so good.
If the tank is full there is 90 ohm between the two connectors of the fuel sending unit which is also correct. Normally the fuel gauge would have to show full but it doesn't ... it only shows 1/4.
When I put a bridge between ground & the return wire on the fuel gauge it shows full but the wire becomes hot.
When I disconnect the two cables of the fuel sending unit the fuel gauge shows 1/2.
Where is the mistake? Is anybody having an idea how to solve my problem? I would really appreciate a solution ...
Looking forward to receiving some lines.
Take care,
Bernd
11-09-2005, 03:41 PM
#2
Le Mans Master
there was a very similar thread on another site about just this same issue. Reading thru it may help you a lot
http://corvetteactioncenter.com/foru...ht=fuel+sender
first thing I'd do though is check your ground on the sender unit and make very sure it's a good ground. Most electrial problems on these cars seem to fall to bad grounds.
http://corvetteactioncenter.com/foru...ht=fuel+sender
first thing I'd do though is check your ground on the sender unit and make very sure it's a good ground. Most electrial problems on these cars seem to fall to bad grounds.
11-09-2005, 04:14 PM
#3
Pro
Bernd,
Hi. I tried to send to you an email via your profile but it was blocked.
I have a troubleshooting guide for Corvette gauges that should be very helpful to you. It goes into details about the fuel gauge and how to troubleshoot a problem.
If you would like this information please send me an email (via my profile) with your email address.
Regards,
GaryC
Hi. I tried to send to you an email via your profile but it was blocked.
I have a troubleshooting guide for Corvette gauges that should be very helpful to you. It goes into details about the fuel gauge and how to troubleshoot a problem.
If you would like this information please send me an email (via my profile) with your email address.
Regards,
GaryC
11-09-2005, 04:23 PM
#5
Burning Brakes
My 66 has 3 wires at the sending unit
1. black => ground (along with light grounds in rear of car)
2. tan = sending unit (round connector)
3. pink => sending unit (flat connector)
however, there are only 2 wires at my gage Tan and pink
Not sure where this 3rd wire is coming from for your 3 wire gage?
how is it you have 3 at the gage?
Chuck
1. black => ground (along with light grounds in rear of car)
2. tan = sending unit (round connector)
3. pink => sending unit (flat connector)
however, there are only 2 wires at my gage Tan and pink
Not sure where this 3rd wire is coming from for your 3 wire gage?
how is it you have 3 at the gage?
Chuck
11-09-2005, 05:18 PM
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Hi Chuck!
I took the gage out of the dashboard for testing. Yes there are of course only two connectors to connect with the plug. The third wire is ground. Normally no extra wire because the gage is connected with the metall of the dash board witch is connected with ground.
Bernd
I took the gage out of the dashboard for testing. Yes there are of course only two connectors to connect with the plug. The third wire is ground. Normally no extra wire because the gage is connected with the metall of the dash board witch is connected with ground.
Bernd
11-09-2005, 08:25 PM
#7
Burning Brakes
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Bernard
There are a lot of other posts on the fuel guage system that you can read up on. Most important is that this system isn't a resistive system - it's actually a voltage divider so reading ohms tells you some things but not all.
When you put a bridge (that's German for a short) between the tan wire and ground - the gauge read full. That's perfect. It's supposed to. So your guage is OK. The wire gets hot because of the current you are sinking through the guage to ground. The bridge between ground and the sender wire is a good test but only a test that you don't leave hooked up long.
You do have three wires at the tank sender but the only wire that actually goes from there to the guage is the tan one. The 12V wire and the ground are independent from 12V wire and ground that feed the gauge. If you read a good 12V on the 12V wire at the sender and at the gauge, then I would tell you that you have a bad ground somewhere that is causing your voltage divider to give a bad reading. Take a seperate wire and attach it to a real good ground somewhere on your car. Take the other end of that wire and ground the sender. See if your gauge reads right. If it does, then the ground feeding the sender is not good. If it doesn't change the reading, then reach under the dash with that wire that is connected to the good ground and ground the case of the fuel gauge. Does it read right now? Let us know.
Spater und viel Gluck (sorry - no umlauts)
Geek
There are a lot of other posts on the fuel guage system that you can read up on. Most important is that this system isn't a resistive system - it's actually a voltage divider so reading ohms tells you some things but not all.
When you put a bridge (that's German for a short) between the tan wire and ground - the gauge read full. That's perfect. It's supposed to. So your guage is OK. The wire gets hot because of the current you are sinking through the guage to ground. The bridge between ground and the sender wire is a good test but only a test that you don't leave hooked up long.
You do have three wires at the tank sender but the only wire that actually goes from there to the guage is the tan one. The 12V wire and the ground are independent from 12V wire and ground that feed the gauge. If you read a good 12V on the 12V wire at the sender and at the gauge, then I would tell you that you have a bad ground somewhere that is causing your voltage divider to give a bad reading. Take a seperate wire and attach it to a real good ground somewhere on your car. Take the other end of that wire and ground the sender. See if your gauge reads right. If it does, then the ground feeding the sender is not good. If it doesn't change the reading, then reach under the dash with that wire that is connected to the good ground and ground the case of the fuel gauge. Does it read right now? Let us know.
Spater und viel Gluck (sorry - no umlauts)
Geek
11-10-2005, 03:51 PM
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Hi Geek!
Today - Thursday 9 pm - too much food in my stomach, not at all in a mechanic mood ... if you know what I mean ...
. Well I have decided to search the mistake on my gage / sender tomorow evening. Your information will definitely be helpful to solve my problem. Thank`s a lot!
I´ll let you know the results later.
Bernd
Re.: Spater und viel Gluck (sorry - no umlauts)
Gluck = gluck gluck gluck - german meaning for sound when you drink...
Today - Thursday 9 pm - too much food in my stomach, not at all in a mechanic mood ... if you know what I mean ...
. Well I have decided to search the mistake on my gage / sender tomorow evening. Your information will definitely be helpful to solve my problem. Thank`s a lot! I´ll let you know the results later.
Bernd
Re.: Spater und viel Gluck (sorry - no umlauts)
Gluck = gluck gluck gluck - german meaning for sound when you drink...
11-10-2005, 07:00 PM
#9
Burning Brakes
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Bernard,
Ah I do know the feeling. Brat. Bier. Nachmittagsschläfchen. Figured out how to get umlauts. Viel Glück - good luck. But viel gluck gluck gluck works too -- good drinking.
Let us know how your sender thing works out. I am thinking fixing the ground will do it. But if it doesn't, knowing what it did when you give it a known good ground will help us out.
Bis bald.
Geek
Ah I do know the feeling. Brat. Bier. Nachmittagsschläfchen. Figured out how to get umlauts. Viel Glück - good luck. But viel gluck gluck gluck works too -- good drinking.
Let us know how your sender thing works out. I am thinking fixing the ground will do it. But if it doesn't, knowing what it did when you give it a known good ground will help us out.
Bis bald.
Geek
11-12-2005, 01:42 PM
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Hi Geek!
Schön von Dir zu hören! -- www.leo.org -----
Well - all attempts were in vain. I have to order a new sender. My last chance...
I'll keep you informed ...
In the meantime keep on learning and training our beautiful loveley simple language ...
Actually you're doing a pretty good job and I wonder were you learned all the "basics" ... 
Sehr sehr schön!
Viele Grüsse,
Bernd
Schön von Dir zu hören! -- www.leo.org -----
Well - all attempts were in vain. I have to order a new sender. My last chance...
I'll keep you informed ...
In the meantime keep on learning and training our beautiful loveley simple language ...
Actually you're doing a pretty good job and I wonder were you learned all the "basics" ... Sehr sehr schön!
Viele Grüsse,
Bernd
11-12-2005, 02:40 PM
#11
Burning Brakes
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Bernd
The basics? Mein verstorbener Vater. Mein Familienname ist Pfenning. Now I learn/practice from my 18 year old daughter who is a language sponge - speaks English, Spanish, German, and now Russian.
I am going to guess that the extra ground didn't do anything to change the gauge reading. There are two checks you can do on your sender if you want. Disconnect the 12V wire and the tan wire from the sender. On the sender read ohms between those two connections. Should be 0 ohms when empty and 90 ohms when full. Then between the connection where the tan wire was, it should read the opposite - 90 ohms when empty and 0 ohms when full. If they both don't read correctly, then the voltage divider won't work and your gauge will read like it does.
Bis bald.
Geek
The basics? Mein verstorbener Vater. Mein Familienname ist Pfenning. Now I learn/practice from my 18 year old daughter who is a language sponge - speaks English, Spanish, German, and now Russian.
I am going to guess that the extra ground didn't do anything to change the gauge reading. There are two checks you can do on your sender if you want. Disconnect the 12V wire and the tan wire from the sender. On the sender read ohms between those two connections. Should be 0 ohms when empty and 90 ohms when full. Then between the connection where the tan wire was, it should read the opposite - 90 ohms when empty and 0 ohms when full. If they both don't read correctly, then the voltage divider won't work and your gauge will read like it does.
Bis bald.
Geek
11-12-2005, 02:50 PM
#12
Racer
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Is your float not leaking (filled with fuel). If it is it won't float and your gauge will indicate the tank is full.
greetings,
Rob Musquetier
The Netherlands
greetings,
Rob Musquetier
The Netherlands
03-19-2012, 03:50 PM
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cud use the diagram Brand for my 1980 fuel gauge reading empty and 3v at sensor?/help
Cud use the diagram David C. for my 1980 fuel gauge. It's reading empty and 3v at sending? Haven't tried the gauge but ground seemed good at sensor, not sure why the voltage drop as of 3 volts at pink wire on sending unit. Was working fine till last year was running and nearly overheated and saw the gaige go to empty? Thought a wire fried and figured ground? I also took 12 volts external source to the sending unit and no change with key on acc. Then went to put in garage and for split second when started went to full and then bk down to empty? something shorting somewhere? Hence the voltage drop? Anyone with help would be appreciated thanks John tj5435673@yahoo.com
Last edited by tj5435673@yahoo.com; 03-19-2012 at 03:55 PM. Reason: wrong spelling of user name for help
03-19-2012, 06:04 PM
#14
Wilcox reference document
If you need another source, the fuel sender troubleshooting document posted on Willcox site is excellent
http://willcoxcorvette.com/repairand...lp.php?hID=251
http://willcoxcorvette.com/repairand...lp.php?hID=251
03-19-2012, 07:57 PM
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Cud use the diagram David C. for my 1980 fuel gauge. It's reading empty and 3v at sending? Haven't tried the gauge but ground seemed good at sensor, not sure why the voltage drop as of 3 volts at pink wire on sending unit. Was working fine till last year was running and nearly overheated and saw the gaige go to empty? Thought a wire fried and figured ground? I also took 12 volts external source to the sending unit and no change with key on acc. Then went to put in garage and for split second when started went to full and then bk down to empty? something shorting somewhere? Hence the voltage drop? Anyone with help would be appreciated thanks John tj5435673@yahoo.com
