Fuel gauge still not working proberly after replacing sending unit

I just replaced my fuel sending unit but it did not solve ALL my problem with the fuel guage.

I'll explain: With the old fuel sending unit, the gauge would always read either empty or full (never the right level which indicates my sending unit was bad and it may have a second problem); now after replacing the sending unit, it reads either empty or the correct level.

I have read in several places that you should replace a wire harness when replacing the pump assembly (www.rockauto.com) I suspect this may be my problem. I tested the bouyancy of the float and it is fine. It is highly unlikely I need to replace the whole pump assembly since replacing the fuel sending unit included all the wiring within the pump. I also notice that some times when I place the shifter in park or neutral it will begin to work. Also driving down the road, some times it works properly reading the right level or it reads empty. This indicates to me it is probably a loose connection or the bad wire harness, I don't know how to trouble shoot this yet.

Where is this wire harness located?

(I don’t think it is the one in the fuel pump since the wires are soldered directly to the fuel sending unit – which I replaced with the fuel sending unit)

Got any suggestions or ideas?

check with nhtsa or whatever it is, if i remeber rightly, there may have been a recall for this exact problem, just a thought

howardjltx:

I'm going to start calling you Howardjinx, because it seems you have so many problems. I thought you were a rocket scientist! (And Oldsmobile used to be known as the "Rocket" division - I like to call the 3.5L the "baby Rocket")

Seriously think about getting an AlldataDIY.com account for $25 a year. All the info and testing info is in there. Your misery will be solved.

Can I trust you using a voltmeter?

howardjltx:

I'm going to start calling you Howardjinx, because it seems you have so many problems. I thought you were a rocket scientist! (And Oldsmobile used to be known as the "Rocket" division - I like to call the 3.5L the "baby Rocket")

Seriously think about getting an AlldataDIY.com account for $25 a year. All the info and testing info is in there. Your misery will be solved.

Can I trust you using a voltmeter?


Not jinxed, just busy at work with NASA traveling and had to ignore the minor car problems until I got back from multiple business trips before I fixed things back to normal. A fluke in hand wouldn't be a problem, also had a 1967 Oldsmobile 98 convertible with a 455 Rocket in it, I think the space shuttle gets better gas mileage then it did.

Haven’t heard of AlldataDIY.com, when I get a chance I'll look it up.

I know this is 8 months later but did you solve the issue of the fuel guage. I am having the same exact problems as you described.