Over the past 3-4 years of working on T3's we have found the we have dealt with many issues related to dirty fuel and most of these have stemmed from a rusty fuel tank.
Just this week we had a T3 Caravelle in here with a rough running issue that we quickly put down to a blocked injector. Whenever we see a blocked injector we go straight back down the line to the fuel filter and fuel tank. In this case we noticed a small wet patch at the bottom of the fuel tank. As soon as we touched it to have a closer look we saw it was fuel and it started a small stream. Sadly we had to advice the customer he was up for not just an injector but a complete new fuel tank.
The pictures we've put up here show the inside of the fuel tank and the fuel that we drained from the fuel filter. You definitely don't have to be a VW expert to see the problem here.
This is not the first fuel tank we've replaced. Of the maybe 15 to 20 T3's we've worked on we've probably replaced 8 fuel tanks. Whenever we get a lot of the same thing we like to dig down and discover the cause. The root of the problem with dirty fuel tanks in T3's is, like most things, design flaws coupled with poor maintenance.
T3 fuel tanks have three rubber grommets in the top of the tank with air hose running to them that then run up to two breather tanks in the front wheel wells. Over time these grommets harden and crack, as does the air hose. This causes the fuel tanks to collect air which turns to condensation which turns to water and eventually rusts your tank.
The prevention: Replace your breather hoses, grommets and ensure you have a proper sealing fuel cap. Also, check and replace your fuel filter/s regularly. We also recommend fitting, if you don't already have one, an additional fuel filter between the tank and the fuel pump. This will prevent debris from the tank damaging your fuel tank.
What to do if your tank is already dirty? Unfortunately it's time to replace it. If it has rust buildup you can be sure the tank will be rusting from the inside out and said debris will cause damage to the rest of your fuel system from the fuel pump to the injectors and even the fuel pressure regulator.