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I pulled my fuel sending unit out tonight (77), so that I could remove old gas and inspect the condition of the tank. I have a couple of questions about the sending unit. First, I found a small metal pin in the tank. I've included a pic of the pin next to the sending unit. I can tell from the weld mark that it came off the piece that swivels under the filler flap. I can't see that it really serves a purpose, but does anyone know? Before I pulled the tank, I checked and the sending unit works.
My next question concerns the gasket and bolts for the sending unit. Mine has a gasket. A few of the bolts have o-rings on them but not all. I'm assuming the sending unit was replaced at some point. While looking for replacement parts, I found the bolts with o-rings but the gasket alone was a little harder to find. (I did find it though).Then I noticed that some sending units advertised that no gasket is required. So do I need bolts with o-rings or just regular bolts (no o-rings) and the gasket. Both? Just trying to order all that I need at once to reinstall the tank and want to get it right the first time.
#1. The metal pin.
You can see where it's supposed to be welded in this picture of my '77 sending unit:
#2. Gasket or no gasket. O-rings or no o-rings.
I'm not 100% sure, but this is my guess:
If your tank still has an inner bladder and you're planning to use it, you use the old bolts with the O-rings and no gasket. I got new O-rings at a NAPA store.
If you don't use an inner bladder, you use the gasket with bolts+washers+steel ring that was originally embedded in the bladder.
Here's a picture of my bladder (I mean my '77 C3 bladder)
You can barely see the steel ring embedded in the rubber.
And here's the kit I bought thinking I would need it, but I most likely won't:
#1. The metal pin.
You can see where it's supposed to be welded in this picture of my '77 sending unit:
If that is what I think it is, its the emission vapor control valve. There is a ball that floats so fuel doesn't splash into the emission line that runs to your charcoal cannister located inside the front driver's side fender. If those pins are missing...the ball floats in the fuel rather than in its chamber. If that's what it is, find a welder and spot weld it back in place.
Rbrid has it right. It's part of the cross looking piece directly under the fill flap. I could tell that is where it goes because of the weld mark but couldn't really tell what purpose it serves.
I took another look at it this morning. I guess what I thought was the gasket is actually part of the bladder, so I just need to pick up some o-rings to fit the old bolts. Is there a reason not to use the bladder?
Yes, I believe you just need to buy new O-rings. That's what I did, and I refurbished the old bolts.
I think the reason not to use the bladder is when the rubber cracked and lets the gas through. Since it's no longer produced, you can't easily replace it. That's when the gasket comes handy.
Fuel Sending Unit Question
