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While driving my 1968 Olds 98 convertible (455 cu in 4 Barrel) on my Monday morning drive, the car stalled as though it ran out of gas. The gas gage showed 3/8 full. With two gallons of gas from a gas can I was able to start the car. Is there a problem with the gas gage or with the fuel gage sending unit in the car. JCaparts and ebay sell a replacement fuel gage sending unit for $117.00. I spoke to a mechanic and he said you have to drop the tank to get to the sending unit on the top. At the same time he will pressure wash the tank to remove any sludge inside. Am I on the right path to take care of this problem? Anybody else have similar experience.
That is not what the sending unit in your car looks like. You are correct that the fuel tank has to be removed to get at the sending unit as it is mounted in the top center of the tank.
That unit looks like what was used in the A-body cars. The actual sending unit is a hockey-puck-in-a-canister arrangement. There is a vertical shaft, and a rubber float that looks like a hockey puck that slides up and down the shaft in response to the fuel level. This all sits inside a small canister.
Here is the diagram from the 1968 Olds chassis service manual.
I once owned a '67 Delta 88, and it used the same kind of sending unit your car uses. Here is a photo of the sending unit in that car, and it has been partially disassembled.
No one makes replacement sending units like this, so you are correct that you will have to make something else work. In the case of my '67 Delta, I found that a sending unit for a '72 Delta 88 or Buick LeSabre is a drop-in replacement. But there is a difference. The purpose of the canister in the original unit is to dampen the effect of the fuel sloshing around inside the tank as the car goes over bumps and around corners. This prevents the fuel gauge from waving all over the place. Because of this, the fuel tank itself does not have any internal baffles to dampen the fuel movement. The replacement sending is meant for a fuel tank that DOES have baffles, so you will likely notice that the fuel gauge waves at you a bit more than you're used to because it will bounce around a bit as you drive the car. However, I found that this was very minor, and it was very nice to actually have a functioning fuel gauge.
The unit you want is a Spectra-Premium FG106A. It is available at Rockauto for $49 (plus shipping), which is a heck of a lot less than the unit you're looking at. Amazon has it for $57 with free shipping if you're a Prime member. You can also likely get it through your local NAPA or Autozone, but the price could be higher.
One last comment: I'm not saying that the sending unit your mechanic wants to use won't work. I imagine anything that has the correct mounting flange and that sticks far enough down into the tank to suck out most of the fuel will work. I just know that the unit I described WILL work, and it costs less than half as much.
Last edited by jaunty75; November 9th, 2020 at 07:48 PM.
Thanks Jaunty for the detailed info. I will pursue this option. Any cautions to observe whilst dropping the tank, I believe there is a insulation pad on top of the tank between the tank and the underside of the trunk. If that is in tatters, are those available?
Removing the tank is straightforward. Just remove the bolts at the ends of the tanks straps. But if they're never been loosened in 52 years, don't be surprised if you have to cut them and use new ones. No big deal.
When I removed my tank, I didn't find any pad above the tank on the underside of the trunk floor. I imagine that tank pads are pretty generic, and if you can find anything, you can always cut it to fit.
Rocketraider I am in Houston, Texas. Do you know of any places either in Texas or US that can repair these units.
Have you actually removed the unit that's in your car? Do you know for sure that the sending unit is the problem?
I showed a photo of what your sending unit looks like. There isn't a lot to "rebuild" on them. The rubber hockey puck doesn't deteriorate. The metal shaft it slides up and down on doesn't, either. The filter sock at the bottom is probably rotted away, and there are no direct replacements made. If anything, unless water has gotten into your tank, you'll probably find the sending unit to be in reasonably good shape.
Before I put that Spectra Premium unit in my '67 Delta, I tried to reuse the original sender. About the only thing I could do was clean it. But it is inherently a problematic design because it is relatively easy for the puck to get stuck inside the canister. I think this explains why Olds didn't stick with this design for the big cars very long. That was the problem I had. I cleaned it up as best I could (it was in remarkably good shape, otherwise) and put it back in the car. I filled the tank, and it seemed to work for a few days. Then the gauge got stuck, and I had to lower the tank all over again. I said enough's enough and bought the Spectra Premium unit. With an exposed float, there is no way it can get stuck. I installed it, and the rest is history
As I say, though, I wouldn't buy anything or start hunting around for rebuild shops until you have actually dropped the tank and verified that the sending unit really is the problem and that it's not a bad ground or something like that. From what you said in your first post, it sounds like your mechanic is only speculating that the sending unit is the problem. He has yet to actually look at anything, correct?
Jaunty - last week my mechanic dropped the tank, drained it, cleaned it and replaced the gas gage sending unit. The unit in the tank was not the original (one with the hockey puck). Attached is a picture what came out of the tank. The tank is now 5/8 full. I have to drive it and see if the gage shows accurately. Thanks for your help. I purchased the new one from Amazon ($57.00)
November 9th, 2020 | 05:53 PM
