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Discussion Starter #1
I have examined four 5000 series fuel tanks and found the large rubber like grommet that the fuel pump seats at the bottom of the tank is deteriorating or breaking up. This is apparently used to keep returning fuel separated from the gas tank fuel supply at large.

This is Audi/Volkswagen part number 443 201 746A Gasket.

The North American Dealers no longer supply this part and I'm wondering what the pros are doing to work around this problem. I consider this to be a service hazard as if it breaks up it can get sucked into the fuel pump and plug its inlet screen. Then it's lights out for a very expensive fuel pump and possibly as well for the new one one might install.

Does anyone have a parts source? The number on my part is three audi like rings and then 02 3858 4. Note that Audi has a four ring symbol. I have already searched extensively for this part.

Note that your dealer can print you a very nice drawing of what's in your fuel tank.. A very neglected area, I'm thinking.
 

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Discussion Starter #2
Since posting the previous I've discovered that some of my Audis have the wrong size fuel tank fuel pump grommet installed. In fact the 02 3858 4 posted in my previous is the wrong size. The proper size is 02 3858 7. (The Audi Part number posted previously should be the correct part. The numbers above are not Audi numbers and I do not know whose numbers these are. Whose symbol or Icon is three Audi Like Rings instead of 4?) Anyway, the grommet must fit the fuel pump and if it's too big the pump will suck gas from the unfiltered tank supply instead of from the in tank fuel return supply which is filtered by first your fuel filter and then the screens in the large plastic fuel return device bolted to the bottom inside of your fuel tank where the grommet and the fuel pump are both mounted.

I suspect a short cut mechanic thought he could solve a fuel problem by bypassing the protective device. Such apparent stupidity happens more often than one might expect! Watch out for fuses bupassed with tin foil!
 

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After checking and reviving 5 different 5000 gas tanks it seems that the rubber gastank grommet is more likely than not the wrong size where diameter exceeds the diameter of the fuel pump barrel. This does make one wonder what has been going on with all these different sized grommets in use though all the fuel pumps have the same diameter.. The real trick is to have an immaculate gas tank or you are likely to encounter severe stalling problems, though the car will usually restart right away but then stall again when trying to accelerate. The final result may well be the failure of your very expensive in tank, electric fuel pump. The good thing is that the injection system is very robust in recovering from a crudded up gas tank after the tank has been cleaned and the fuel filter replaced. Never replace a fuel pump without checking for crud on the bottom of the tank.

I found a unique method used to get around the dirty fuel tank problem in a parts car purchased today. The owner had installed a fuel pump outside the tank, but near the fuel tank access port in the trunk. However, this may not be a good idea for several reasons though the car is still running: A spark here from the electrical connections with the gas tank cover off could cause quite an explosion! The pump is also designed to cool itself while submerged in the fuel and when submerged in fuel a loose electrical connection has no opportunity to ignite an explosion.
 

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5000 fuel tank

Help? Do I need to drain the fuel tank on my 83 Audi 5000 diesel if it has been sitting exposed to the weather over 3 years? If so, how does one go about getting it safely drained?

Harvey Smith said:
After checking and reviving 5 different 5000 gas tanks it seems that the rubber gastank grommet is more likely than not the wrong size where diameter exceeds the diameter of the fuel pump barrel. This does make one wonder what has been going on with all these different sized grommets in use though all the fuel pumps have the same diameter.. The real trick is to have an immaculate gas tank or you are likely to encounter severe stalling problems, though the car will usually restart right away but then stall again when trying to accelerate. The final result may well be the failure of your very expensive in tank, electric fuel pump. The good thing is that the injection system is very robust in recovering from a crudded up gas tank after the tank has been cleaned and the fuel filter replaced. Never replace a fuel pump without checking for crud on the bottom of the tank.

I found a unique method used to get around the dirty fuel tank problem in a parts car purchased today. The owner had installed a fuel pump outside the tank, but near the fuel tank access port in the trunk. However, this may not be a good idea for several reasons though the car is still running: A spark here from the electrical connections with the gas tank cover off could cause quite an explosion! The pump is also designed to cool itself while submerged in the fuel and when submerged in fuel a loose electrical connection has no opportunity to ignite an explosion.
 

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Discussion Starter #5
5000 diesel fuel tank

I'm thinking parked Diesel Audis should have much less problems in the fuel tank than do the gas models.. Diesel has lubricating properties that should make fuel pump seize up much less of a problem and help to keep the tank clean.. If you have a gas model sitting around make sure you start it at least twice a year. Keep the tank full of a better grade fuel.. I'm assuming it will have better anti seize additives than regular.

If you've left your gas Audi parked for over a year keep your fingers crossed when you try to start.. Also never leave a connected battery in a parked Audi.. It will be dead probably after a month or so and toast.

It seems that fuel tank grommet isn't really needed at all! There are some aftermarket pumps and later Audi designs that attempt to keep it from sucking up muck from the tank bottom. The regular pump works fine if the tank is clean and you start it on occasion as above.

Just in passing, if your fuel pump quits you might need to wiggle the Fuse Box around.. It has electrical connectors on the bottom that may need invigorating. This worked for me on one of mine and I have heard of others with the mysterious no start problem that seems possibly related. (Driver side under the hood near dash)
 
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