Gas Tank Replacement

Hello Folks,

I recently decided to bite-the-bullet and replace the gas tank on my 2008 Prius. I’d like to share my results and some notes for the community.

The symptom I was having was that the gas gauge would drop from full to one flashing dot in just 100-200 miles. The last 5 pips would typically disappear in just 20-30 miles. When I filled up I could only get 2-4 gallons pumped in before the pump would shut off. Pumping with the nozzle rotated or pumping slowly made no difference. The problem was worse in the winter when I would typically get only 2 gallons when the gauge read empty. In the summer I would typically get in 4 gallons.

I replaced the tank assembly with a new one 2 weeks ago and have driven over 1000 miles and 3 fill-ups. I traveled >370 miles from full to two dots on each tank with the fill taking 7.5-7.8 gallons. I’m satisfied that the tank and fuel gauge are now working properly.

I found that the old tank had about 6 gallons of gas in it when I removed it. There were about 3 or 4 pips on the gas gauge before I removed it, so I concluded that the problem was caused by a faulty sender rather than a problem with the bladder itself. Even though the problem was in the fuel sender, I still had to replace the tank since the sender is not a component you can replace separately.

My notes:

· The parts I used were a fuel tank assembly (PN 77001-47090) and two gaskets (77179-33010). The gaskets are rubber “donuts” used for two components (pressure sensor adapter and trap canister) that penetrate the steel shell of the tank.

· I did the job alone and it took about 12 hours in total. It was quite a complex job and was fairly physically demanding.

· I did not remove the exhaust pipes in order to avoid breaking the exhaust fasteners. This made the job much more difficult and time consuming due to the time required to work the tank into place around the exhaust. I had to temporarily move the driver’s side parking brake cable and the plastic guard in front of the rear DS tire to make room to shift the tank in around the exhaust.

· I had to support the tank with 2 floor jacks during the installation process in order to be able to control the angle of the tank while raising it into the minimal clearance around the exhaust pipe. I had to use some pieces of wood to distribute the load from the small jack faces to avoid damaging the exterior of the tank.

· Removing and reinstalling the connection to the filler neck is the worst part of the job. The pipe to the filler neck has “accordion” ridges which make it appear to be flexible, but it feels as stiff as a straight pipe. The tank installation instructions suggest moving the tank up onto the pipe rather than installing the tank and then sliding the pipe up onto it, and this is the correct process since you can maneuver the tank much easier than you can move the pipe.

· There are a bunch of components mounted on the tank that you have to move to the new tank. I found it easier to leave most of the external components connected to each other and move them as a group. This allowed me to avoid disconnecting some of the tubes that go between them, which I thought was a good idea since disconnecting/reconnecting them could cause leaks.

· I found no gas in the charcoal canister when I transferred it to the new tank.

Rex