R & R fuel tank sending unit.
#1
Safety Car
Thread Starter
R & R fuel tank sending unit.
My fuel tank sending unit is leaking a little bit on my 63 coupe.
Has anyone done the R & R of the sending unit WITHOUT removing the spare tire tub? It looks tempting to try.
Where would the best place be to go to get a new SU gasket?
Has anyone done the R & R of the sending unit WITHOUT removing the spare tire tub? It looks tempting to try.
Where would the best place be to go to get a new SU gasket?
#2
Race Director
I would recommend BOTH a new GM gasket and a new GM metal sending unit retaining ring. Both are available on Ebay, if you search under the original part numbers. I can provide if needed. Reproduction o-rings from OEM Reproductions are also very nice, and I would use it if I could not find the GM piece. I would not use anything else.
Soak o-ring in motor oil overnight or use Vaseline on it.
The sending unit requires a bit of "moving it around" inside the tank to get it thru the gas tank opening............but it can be done. If you have an original sending unit, the electrical posts (2) have adjustment nuts to provide sealing of these connections. Maybe you just need a simple adjustment of these retaining/sealing nuts.
Larry
Soak o-ring in motor oil overnight or use Vaseline on it.
The sending unit requires a bit of "moving it around" inside the tank to get it thru the gas tank opening............but it can be done. If you have an original sending unit, the electrical posts (2) have adjustment nuts to provide sealing of these connections. Maybe you just need a simple adjustment of these retaining/sealing nuts.
Larry
Last edited by Powershift; 08-20-2018 at 11:45 AM.
#3
Team Owner
I removed the spare tire tub to change mine. It was a little effort but resulted in easier access and visibility. Disconnect the battery while doing the work. C2 sending units are “powered”.
#4
Safety Car
Thread Starter
I would recommend BOTH a new GM gasket and a new GM metal sending unit retaining ring. Both are available on Ebay, if you search under the original part numbers. I can provide if needed. Reproduction o-rings from OEM Reproductions are also very nice, and I would use it if I could not find the GM piece. I would not use anything else.
Soak o-ring in motor oil overnight or use Vaseline on it.
The sending unit requires a bit of "moving it around" inside the tank to get it thru the gas tank opening............but it can be done. If you have an original sending unit, the electrical posts (2) have adjustment nuts to provide sealing of these connections. Maybe you just need a simple adjustment of these retaining/sealing nuts.
Larry
Soak o-ring in motor oil overnight or use Vaseline on it.
The sending unit requires a bit of "moving it around" inside the tank to get it thru the gas tank opening............but it can be done. If you have an original sending unit, the electrical posts (2) have adjustment nuts to provide sealing of these connections. Maybe you just need a simple adjustment of these retaining/sealing nuts.
Larry
#5
Safety Car
Thread Starter
#6
Race Director
Here you go. https://www.ebay.com/itm/NOS-3774937...item1ee77168b6
If yu don't buy this kit, then search individually on Ebay using the GM Part #.
Larry
If yu don't buy this kit, then search individually on Ebay using the GM Part #.
Larry
#7
Safety Car
Thread Starter
Here you go. https://www.ebay.com/itm/NOS-3774937...item1ee77168b6
If yu don't buy this kit, then search individually on Ebay using the GM Part #.
Larry
If yu don't buy this kit, then search individually on Ebay using the GM Part #.
Larry
Now I have a couple of questions:
1. What wears out on the cam retaining ring?
2. My needle has always been 'bouncy' on corners & stopping. I have written it off as some baffle missing/out of place in the tank. Could a bouncy needle be due to the sending unit?
#8
Team Owner
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colo63sw (08-20-2018)
#9
Melting Slicks
I just replaced one last week on my Camaro. It was very easy to test to see if it was the SU or the gauge because it’s a simple resistor and not powered. All you do is ground it to see what the guage does. Is there a similar test for the Corvete SU?
Ed
Ed
#10
Race Director
#11
Team Owner
#12
Team Owner
The problem with the repro rings and "O" gaskets are that the metal rings seem a tad smaller and if you don't get it EXACTLY centered you'll have leaks; likewise the repro "O" gaskets are smaller and don't always seal well and will leak. Having the sending unit tool for this job helps but a small hammer and brass "drift" will work but takes some effort to center the ring...
Guess which "O" ring is NOS ?
Last edited by Frankie the Fink; 08-20-2018 at 04:09 PM.
#13
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Member Since: Feb 2007
Location: Northern California CA
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The problem with the repro rings and "O" gaskets are that the metal rings seem a tad smaller and if you don't get it EXACTLY centered you'll have leaks; likewise the repro "O" gaskets are smaller and don't always seal well and will leak. Having the sending unit tool for this job helps but a screwdriver will work but takes some effort to center the ring...
Guess which "O" ring is NOS:
When I removed my "O" ring from my tank, it still feels very pliable. I'm considering using the original "O" ring again. Do you think I should give it a shot?
Also to colo63sw,
I sent my sending unit (pretty sure original too), into John Wolf for a rebuild. Figured I would do it now, rather than put it together to find it didn't work. Something you may want to consider.
Pat
Last edited by ptjsk; 08-20-2018 at 04:10 PM.
#14
Team Owner
If yours is original and not swollen to the point of not sealing, nor brittle, nor cracked -- hell yeah I'd use it...
I thought I'd never get my repro O ring to seal; a forum member took mercy on me and sent me an NOS O ring as a favor....that "sealed the deal"...
Install the "O" ring and put just enough gas in the tank to cover it an inch or two and let it sit overnight...if its OK add a few gallons more and recheck....after about 1/4 tank it should be fine if you want to fill it up...
I thought I'd never get my repro O ring to seal; a forum member took mercy on me and sent me an NOS O ring as a favor....that "sealed the deal"...
Install the "O" ring and put just enough gas in the tank to cover it an inch or two and let it sit overnight...if its OK add a few gallons more and recheck....after about 1/4 tank it should be fine if you want to fill it up...
Last edited by Frankie the Fink; 08-20-2018 at 04:13 PM.
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ptjsk (08-20-2018)
#16
Team Owner
Member Since: Oct 2000
Location: Washington Michigan
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Photos below show an original AC sending unit (top photo) and a Fargo reproduction sending unit (bottom photo) - note the STAMPED "S" and "I" adjacent to the terminals on the original AC unit. Fargo was the best repro unit out there when I wrote the comparison article about eight years ago, but I think they've since gone out of business.
If you have an original AC sending unit, send it to John Wolf & Co. for restoration.
If you have an original AC sending unit, send it to John Wolf & Co. for restoration.
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ptjsk (08-20-2018)
#17
Le Mans Master
He's done a few for me and they work perfectly. Never had a leak using the available o-rings from all the common vendors. No need to search for an old OEM one. A little engine oil for lube is all that's needed.
#18
Safety Car
Thread Starter
Photos below show an original AC sending unit (top photo) and a Fargo reproduction sending unit (bottom photo) - note the STAMPED "S" and "I" adjacent to the terminals on the original AC unit. Fargo was the best repro unit out there when I wrote the comparison article about eight years ago, but I think they've since gone out of business.
If you have an original AC sending unit, send it to John Wolf & Co. for restoration.
If you have an original AC sending unit, send it to John Wolf & Co. for restoration.
Here is a photo of my unit. Sorry about the focus, but it looks like there are stamped letters. Funny thing, I took the photo because I recalled a spade lug on the unit and thought it was one of the (I thought only 2) terminals. I am getting too old.
The new fuel line is my splice because I though the problem was a leaky FL connection.
Thanks again!
Last edited by colo63sw; 08-20-2018 at 09:43 PM.
#19
Team Owner
My repro sending unit had the stamped "S" and "I" letters at the terminals....it also had "90 ohms" stamped on the internal mechanism...
The "I" is the switched 12V from the ignition (remember C2 units are "powered") and the "S" is the wire from the gauge to the wiper of the sending unit's voltage divider circuit...
The difference in the NOS and repro "O" rings is blatant - if you play with a repro part enough I guess you can make anything work......
Here is the 1967 GM Chassis Manual procedure for R&Ring the Corvette sending unit - nothing about soaking the gasket in any goo - it does nothing but make it slippery and hard to install as you'll find out when its slithering around in its groove while you're trying to get the retainer ring on while working upside down...
The "soaking in oil" step is needed to swell the smaller repro gaskets; not required on correctly sized NOS versions. I don't use any oil and GM didn't think it necessary either.
The MOST important thing is to clean that gasket groove and the back of the retainer ring thoroughly - I use lacquer thinner and a lint free rag.
The "I" is the switched 12V from the ignition (remember C2 units are "powered") and the "S" is the wire from the gauge to the wiper of the sending unit's voltage divider circuit...
The difference in the NOS and repro "O" rings is blatant - if you play with a repro part enough I guess you can make anything work......
Here is the 1967 GM Chassis Manual procedure for R&Ring the Corvette sending unit - nothing about soaking the gasket in any goo - it does nothing but make it slippery and hard to install as you'll find out when its slithering around in its groove while you're trying to get the retainer ring on while working upside down...
The "soaking in oil" step is needed to swell the smaller repro gaskets; not required on correctly sized NOS versions. I don't use any oil and GM didn't think it necessary either.
The MOST important thing is to clean that gasket groove and the back of the retainer ring thoroughly - I use lacquer thinner and a lint free rag.
Last edited by Frankie the Fink; 08-21-2018 at 08:21 AM.
#20
Le Mans Master
GM did indeed use engine oil and Quanta recommends it as well when replacing the sending unit. Here's a previous thread on the subject for the non-believers - https://www.corvetteforum.com/forums...ding-unit.html
Repo. seals work perfectly IF they are installed correctly.
JohnZ states - "In the plant, we kept the fat rubber O-ring seals in a tray of motor oil for several hours before installing them; the requirement to do that is in the Assembly Manual, in the "Lubricants" section that decodes the lube symbol on the sheet that shows the installation."
Repo. seals work perfectly IF they are installed correctly.
JohnZ states - "In the plant, we kept the fat rubber O-ring seals in a tray of motor oil for several hours before installing them; the requirement to do that is in the Assembly Manual, in the "Lubricants" section that decodes the lube symbol on the sheet that shows the installation."
Last edited by 1snake; 08-21-2018 at 09:02 AM.