Empty!? Troubleshooting a Brand New Fuel Sending Unit

This should help anyone who installed a Spectra Premium SP2098H fuel pump assembly in a 1989-1997 Ford Thunderbird or Mercury Cougar and found that the fuel gauge was stuck on empty.

My Carter brand replacement fuel pump on my 1996 Ford Thunderbird quit working after about 50,000 miles. Luckily for me, it was in the driveway and just wouldn't start. When I turned the key to 'on', there was silence. I didn't hear any fuel pump noise from the tank.

Tank Drop, Part One

I dropped the tank and pulled the fuel pump assembly out and found that the terminals were burnt on the inside-tank side of the connector. Hey, at least the fuel tank didn't explode. Maybe the fuel vapor concentration was above the upper flammability limit. The actual fuel pump was still functional, but since I bought it as an assembly, and it had a lifetime warranty, I took it back to the auto parts store and traded it out for a replacement assembly.

I thought it was a pretty easy fix, but when I got it all back together and filled the tank, the fuel gauge read empty.

Tank Drop, Part Two

After a couple weeks, I dropped the tank again and diagnosed the electronics. The sending unit read as expected, about 14 ohms when empty, and about 160 ohms when full. When I moved the float, gauge also moved, slowly as usual.

So I figured we're good to go and re-assembled my car. I filled the tank and guess what? It read empty. I decided the float wasn't floating. I was half right.

Tank Drop, Part Three

So today I dropped the tank again. It only took 20 minutes to jack up the car and take off the exhaust pipe and drop the tank down far enough to get at the fuel pump. I filled a bucket with gasoline to see if the float . . . floats.

Sure enough, the float floats. The only remaining problem could be that the float was binding against something, preventing movement. There's a baffle inside the tank that the fuel pump assembly sits in. This float is different from the original, and contacts the baffle. If you take a look at the Motorcraft part PFS185, you'll see that the float does not extend so far to the left.

I'm pointing to the side of the float that was binding against the inner-tank baffle.

First try at bending the float - didn't work

After bending the float, I re-installed the unit back in the tank and inspected it for proper operation. There is a vacuum line with what looks like a check valve on the top of the tank. Removing that check valve revealed a hole big enough to insert my inspection camera through. I lifted the float using the magnet on the end of the inspection camera. Here's what I saw on the inspection camera.

First try

After lifting the float, it didn't fall back down, but got hung up on the side of the baffle. I didn't bend it far enough. So I had to take it out again and bend the float some more. Here's what the float looked like after bending it again.

Float orientation that worked

 After re-installing the pump assembly again, the camera showed sufficient clearance between the float and the baffle. I used the magnet on the end of the camera to verify that the float moved up and down freely when installed in the tank.

I put the fuel I used to test the float, and the rest of that can into my tank. After filling the tank at the gas station, it showed full. Yay!

Why didn't I just return the unit? I figured it would be way more hassle than it's worth to try and find another brand that fits. This got the job done. Oh, and I wore my safety glasses the whole time while working on this (for those of you who read my post on safety glasses).