How to test, clean and protect the fuel sending unit from corrosion
On the road to getting the ’89 944 Turbo back on the road, I continue to come across things that need attention. The fuel sending unit is no exception.
The fuel sending unit in the Porsche 944 is a 3 in 1 device. It’s number one job is to provide a fuel level to the fuel gauge in the gauge cluster. Second, it’s the return line for any unused fuel that was sent back to the tank. And third, it’s a pressure and moisture relief system for the fuel tank.
The fuel sending units return pipe appears to not have had any gas run through it for a long time. This is likely caused by the fact that the car hasn’t run in over 4 years and the fuel return line under the car was severely pinched. The return line was pinched so bad that I don’t think any fuel could return to the tank.
So needless to say, I took it upon myself to try and salvage it. But first I needed to test it to make sure it was even worth salvaging. Check out the video below to see what I found.
Items and Tools used in this video
- Inexpensive Volt Meter: https://geni.us/cvoltmeter
- Exact Volt Meter I Used: https://geni.us/kleinmeter
- Epsom Salts: https://geni.us/epsomsalts
- White Vinegar: https://geni.us/white_vinegar
- Zinc Plates: https://geni.us/zincplates
- Porsche 944 fuel tank Sending Unit and Gasket: http://bit.ly/fuelsender
Resistance Level Testing of Fuel Sending Unit
- Connect an ohmmeter between terminals 1 and 3 on early 944s, or G & T on later 944s, on the sender.
- With the float all the way down, the resistance should read approximately empty resistance (see table below for specific resistance for your model year).
- Slowly move the float up while watching the resistance reading. As you move the float up, the resistance should slowly decrease to approximately 3 ohms with the float all the way up.
- The decrease in resistance should be fairly linear and smooth. If you notice any inconsistent changes in resistance, then the sender is bad or needs additional cleaning.
- If the tests show bad resistance readings regardless of cleaning efforts, the sender should be replaced.