Fuel Sending Unit?

I am in the market, rather desperately, for a fuel sending unit for my wagon. My gas gauge stopped working and I'm really getting tired of photographing my odometer each time I gas up. So far, it's proving to be a difficult search.

Would a fuel sending unit for a '71-'72 Caprice work on a '75? Is there any difference between those designed for wagons versus those for other Caprice body styles?

Thanks in advance for any advice!

 

Fuel sending units differ between wagons and other models, so you really want one for a B-body wagon. (no difference between 71-76)

What makes you think you have to completely change the unit? Isn't it just a wire that has been broken?

Did you measure the resistance?

(GM from '65 and up used zero (empty)-90 Ohm (full)sweep).

 

Let me know if your sender is bad. One of the evil guys here in town has two caprice's wagons that are going to be sacrificed later this year, they both have tanks in them yet and I am sure he will donate the sending units if I pull the gas tanks for him

 

They can also be refurbished.
A rad shop can often repair them.
There is also one place on line that does it, but you will probably be able to find a replacement too.

EDIT: Hey rockauto.com has them listed.

 

I'm a bit embarrassed to admit this, but it was my mechanic that determined my sending unit is bad. He said he tested for electrical connectivity and found no problem.

HARRY~Thanks for the details on this! Now it makes more sense. My gauge has been stuck on "E" but on random, rare occasions, the needle will twitch and try coming back to life; only to die and return to "E" mere minutes later.

SWANNY~Wow, what a great connection you have! Maybe I'll take one of those units regardless, just to have one on-hand. PM me with detail$? Thanks for offering!
My tank is new, but I didn't replace the unit when the tank went bad; guage was working fine when my original tank sprung a leak. Is that guy parting out those two wagons? What else might he have?

HANDY~Thanks for this idea. Once the tank is dropped and the unit pulled, I'll explore this option too. Gosh I wish I could this one myself!

 

Could be a loose wire, bad ground, bad gauge, bad or sticking float! RockAuto can send you one in about a week. My new signal light switch for the 1955 Chevy was as cheap as the shipping. But I'll never have to replace it again. My new fuel gauge kept hanging up in the tank. Minor tweaking and it works great. When in doubt take it out and play with it. And just why can't you do it yourself?

 

A gauge stuck on E means a short circuit. If the circuit were open, the needle would peg at F or possibly go past it as open circuit would mean infinite resistance, and, as noted, the F position means 90 ohms resistance. The fact that your gauge twitches once in a while suggests the short is intermittent.

If you haven't done so, you can check what your mechanic did very quickly. Find where the wires attach to the top of the sending unit, which I think you can get at with these wagons without having to remove the tank, and simply remove the orange (I think it's orange) wire. That would open the circuit and cause your gauge to immediately, with the key on, move to F. If it does that, there is nothing wrong with your dash gauge and the wiring leading to it. If it stays on E, then you need to trace that orange wire all the way up to where it connects to the rear of the gauge and look for a short.

I don't know if it's the same on Chevy wagons, but I also have clamshell wagon, a '73 Olds Custom Cruiser, and removing the gas tank to replace the sending unit (or for any other reason) is no picnic. You need to disconnect and drop the axle on the left side to be able to drop the tank. To do this requires removing the left rear wheel, brake drum, and shock absorber. You also have to support the car independently of the axle so that the axle can be dropped, but not too far because you don't want to damage the brake hose, and it can only be stretched so far. This is by far best done with the car on a lift rather than trying to do it on jack stands in your garage.

I hope that you don't have to do all this and that the problem turns out to be in the wiring between the sending unit and the gauge and not the sending unit itself.

 

Is this sending unit also part of the float , filter and discharge line for fuel to the engine .... if so the line size is important to know ... hypos and big blocks usually had a 3/8th inch line and the smaller engine had the 5/16ths the units are different in that respect..

 

I second what Jaunty says.Pull the wire= full on the gauge,Ground the wire and gauge should go to empty.If the gauge wont move off E then start looking at the harness for a short to ground Somewhere.Good luck...

 

Thanks Cat! Rock Auto looks like a great resource for a lot of stuff! I checked them out and unfortunately, they could not confirm that the sending units they DO have for '75 Caprices would fit the wagon body style (only coupes & sedans... story of my life with this project :banghead3. Reason I can't do much on this myself is b/c the tank is vertically situated inside the rear quarter wall, barely aft of the rear axle. The connections to the tank are near the top, ie: somewhere below the rear wrap-around windows. That means the tank needs to be dropped to get at the connections. I agree, I think this could be a loose wire sticky float or bad ground; the gauge itself I think is okay. Thanks again for the Rock Auto referral tho, I've saved them in my bookmarks!

 

Hey Jaunty,
Oh my gosh, if you know how I might access the connections at the top of my tank w/o dropping the tank again, I'd be forever grateful. I'd LOVE to be able to troubleshoot this further myself and I'm kinda convinced after reading everyone's replies here, that my problem is a bad ground or loose connection at the tank end. (I think the gauge and connections there are fine). Have you had to do something like this on your clamshell?

Thanks so much to you and everyone for your replies and advice!

 

Correct. The station wagon sending unit is different. I've never found a source of new ones for the wagons.

 

I have cut a hole in my trunk, underneith the sidemoldings to access the sender unit. My sender was out of order, and couldnt find a new one, so i used a sender from a G20, the same car that donated the drivetrain to my car.. Just replacing the leveller for the floater.. No problems at all, just pinching the G20 leveler off, prying the estate one on..... Unfortunally i cant get any pics of the operation since the shop computer is broke..

 

No updates since my last post, just haven't had the time to take my wagon back to the shop. Funny how something so "little" is getting me so down. I hate having to take a picture of my odometer every time I gas up. I think after the holidays I'll take 'er back in to have the tank dropped, connections double-checked...and the unit rebuilt if that's an option.
Thanks again everyone for your responses and advice. I'll update you all when I know more.
Merry Xmas and Happy Holidays All!

 

You know, there was a time before digital cameras, and you wouldn't have done this to keep track of gas usage.

Why not do what you would have done in 1960? Keep a pencil and a small pad of paper in the glovebox or ashtray or something like that and just jot down the mileage when you fill up.

Or move up to 1980s technology, get a pad of sticky-notes, and keep your jotted-down mileage stuck right there on the dash somewhere next to the gauge. Not necessarily the most elegant solution, but it gets the job done.