Replacement Fuel sender unit - easy or nightmare??

[Matt C]

Seeing the wealth of knowledge in the forum on everything from the meaning of life to how to align headlights for the continent, I would like to call on your collective experience with a simple problem.

I have just filled my passat 4 motion with £55 of diesel, started the car to drive away and .......PING "Please Refuel", range shows 15 miles and the gauge shows empty. After approx 1 hour the gauge has steadily (but slowly) risen to full and the range has returned to it's expected score of 550-580 miles.

I suspect a punctured float in the sender unit, is it easy to access and change or should I just live with it and go for a beer?

[Lex Luthor]

I have a feeling that the 4motion has a split fuel tank that relies on a transfer pump.
Maybe an expert will be along soon.

[onzarob]

i havn't seen the float on a 4motion, but i would say test your fuel gauge firt as they are know to fail.

look here.

http://www.bba-reman.com/content.asp...ssat_dashboard

it may not be your exact dash but the same fault occurs on the A4 also.

If you want to check the float, I have taken one out of a 2000 passat and they are access through the boot floor, you should see a tupperware type screw lid and it lifts out.(carefully) as there are fuel pipes and wires that go to the tank, i did see somewhere (can't find it at the mo) where some snapped the pastic bits. but good pictures.

Rob

[Matt C]

I thought about the dial but as the computer read-out kept pace with dial I suspect the problem comes from the data sent to both.

I guess my week-end may have to start with seeing how many screws and misc plastic parts I can drop through the hole in the boot, never to be seen again.

Thanks for your comments much appreciated

[onzarob]

Be carefull don't drop them in the tank, I nearly did

Good luck

Rob

[Lex Luthor]

I have a feeling that the 4motion has a split fuel tank that relies on a transfer pump.
Maybe an expert will be along soon.

"Function of suction-jet pump
The fuel tank is separated into two chambers on vehicles with four-wheel drive. In order to move the volume of fuel from the left-hand to the right-hand chamber and then into the reservoir housing of the fuel pump, a suction-jet pump is used.
A second suction-jet pump is located in the right-hand chamber of the fuel tank and improves the supply of fuel to the reservoir housing of the fuel pump.
The suction-jet pumps work based on physical principles and are driven by the fuel return system via a T-piece with pressure limit valve."

From the symptoms you have a "slow" pump.

Oh, and you have three senders........
Have fun......

[Matt C]

Gee thanks Lex, interesting interpretation of the word fun . I've now gone from a possable dodgy sender to 3 transfer pumps and 3 senders, I'll bet the problem will the least accessable unit which can only be reached by removing the tank, probably requiring removal of the rear drive train and with my luck the front bumper for good measure.

On a serious note thanks to all for the help and advice it's great to find a forum like this which is closely watched by so many people, who are ready to pass on this info.

[mcstu74]

I had this exact problem about 2 years ago when I was using normal unleaded fuel in my Passat (instead of the good stuff - V-Power). The problem was a sticky sender & the cure was to put a bottle of fuel cleaner in the tank. It may happen with diesel too (not entirely sure how much deposit it leaves). I suspect you just need to dump a cleaning solution of some sort in your tank.

Cheers
Stuart

[Matt C]

Good news (for me anyway) a high speed thrash and two fill ups and the problem has now cleared (for the moment at least). Up till now I have been using "Super Plus" but decided for the last two fills to use standard diesel which seems to have solved the problem, so I suspect Stuart is right and deposits are to blame.

[Lex Luthor]

Glad to hear it's sorted and you had minimal "fun"......