Sending Unit Question

ok, 2 questions...

Hi, new here... did post in introductions.

93 RMW

Yesterday I began smelling raw fuel near the rear of the car. I have been doing some searches here on the sending unit and fuel lines on the top of the tank.

Before I drop the tank, I want to be ready.

If the car still runs well despite the fuel smell, the sender is probably fine??

Be ready to replace the O-ring and lines?

I figured I order the the O-ring at least and look into those patch hoses....

The tanks have a history of leaking from the top. It may be the tank itself. It could also be the vent line to the filler tube. You must remove the tank to determine what the problem is. The sender is probably OK, although one of the lines could be corroded, or loose in the flange. The vent hose to the filler neck is 18mm, but if you clamp it tightly, a 3/4 inch hose will work. Make sure it is a hose for fuel.

If you disconnect the fuel line from the output line of the filter, and attach a partial line, you can use the pump to remove almost all of the gas from the tank, and put it in a fuel container or two. The tank is not that hard to remove when full, but you should empty it before trying to install it.

The "sending unit" includes hard metal lines that rub against the body and do rust over time. It's likely that one of those lines has rusted, and the best fix is a whole new sending unit. I would not bother with just the big o-ring.

If the 91-93 cars are like the '94-96 cars, I disconnect the output of the fuel filter in front of the driver's side rear wheel and then use the test wire under the hood to pump the tank out.

Thanks for the info!

Simple job. A jack and a properly sized piece of Plywood. Don't have to remove the neck from the tank, heck you don't even have to fully pull the tank from under the car.

94Woody wrote:

Simple job. A jack and a properly sized piece of Plywood. Don't have to remove the neck from the tank, heck you don't even have to fully pull the tank from under the car.

The filler vent hose can be seen at about 1:00 in the pidture. As you can see it is not accessible with the tank installed. Be careful with bending the filler hose, as they are getting old, and can only be replaced with a straight hose, and a diameter adapter for the tank end. Should you need one https://www.fillernecksupply.com/ has them.

There should be a rubber strip where the tank hits the frame. They are usually attached to the frame. If it is missing, an old bicycle tube will work.

Fred Kiehl wrote:

94Woody wrote:

Simple job. A jack and a properly sized piece of Plywood. Don't have to remove the neck from the tank, heck you don't even have to fully pull the tank from under the car.

The filler vent hose can be seen at about 1:00 in the picture. As you can see it is not accessible with the tank installed. Be careful with bending the filler hose, as they are getting old, and can only be replaced with a straight hose, and a diameter adapter for the tank end. Should you need one https://www.fillernecksupply.com/ has them.

There should be a rubber strip where the tank hits the frame. They are usually attached to the frame. If it is missing, an old bicycle tube will work.

No hoses were bent or damaged in the making of that picture. Third time the tank was down that week and everything was unbolted from their mounting points. The entire neck was just left in place because it had no reason to come out from under the car.

There is far more room under there than people think. I'm used to working in much tighter spaces daily. This old wagon is much simpler than say a PACCAR MX-13 stuffed between the frame rails of a Peterbilt 579. MAXXFORCE 15 turbo replacements, that's an exercise in flexibility.

Wrestle one of these beasts out from under a 25 year old dump truck and a full B Body fuel tank is a joke.



Had one slip off the jack once after I got it back under the truck (in my current shop without that fancy 4 post lift) that took some grunting and groaning to get back in place, lol.

You may be in better shape than most of old farts who own these antiques. When I was 46, I did a lot of stuff that I have trouble doing now.

You are correct on that one. Although I will say that even at 46 work is no longer very easy. Doing this crap every day for 20+ years is taking it's toll.

If the sending unit lines are rusted out, you can fix them for ~$20 vs ~$100 for a new sending unit/lines. Not always the best option, but something to consider.

See post below

https://www.impalassforum.com/threads/what-did-you-do-to-your-wagon-this-week.260225/post-12138464

Fix Until Broke wrote:

If the sending unit lines are rusted out, you can fix them for ~$20 vs ~$100 for a new sending unit/lines.  Not always the best option, but something to consider.

See post below

https://www.impalassforum.com/threads/what-did-you-do-to-your-wagon-this-week.260225/post-12138464

There is no fix for rusted out sender lines. A new sending unit is the only "fix".

OK. I don't want to derail or hijack this thread so please forgive me. One of the things I'm planning to do to my RMW is to take the fuel tank down, clean it, and replace the fuel pump. For all I know it could be the original pump but it has worked well so far. I've been reading a lot of things about Delco and other fuel pump assemblies failing because the pressure hose is of poor quality and also the wiring. What do you think of me pulling my assembly out and just replacing the fuel pump itself? I'd install new wiring and put a new sock on it. My fuel gauge reads perfectly and I don't really see that I want to replace a known-good American unit with some Chinese crap of uncertain quality. What pump unit would be the most reliable from your experiences?

Is the pump available separately??

Yes the pump is available separately. Get the original AC Delco, Delphi, or Walbro. Make sure you note what engine you have for the correct unit.