Blocked inline filter

Is the filter a cartridge type, if so change it and drain the tank. I had a problem a few years ago with a rusting tank (long story) and I found that the rust was in the fuel and blocking the filter. For me, it ended up being a big job to get sorted, but I got there in the end. Good luck.

Have a read of THIS ARTICLE.

I know it's about the issue in boats but the same can happen in all fuel tanks.
The most common cause in road vehicles is a continuously partially filled tank, the air space presents the opportunity for condensation within the tank which supplies the water which promotes the formation of the algae/bacteria mentioned in the article.

Good advice to minimise the problem is to keep the tank full when parked up for long periods, thus reducing the surface area where condensation can occur.

My local FIAT Professional foreman mechanic once told me that many people who come in with engine problems saying they got 'dirty diesel' somewhere, when questioned said the usually just put €20 or €30 of fuel in when the light comes on and rarely have the tank more than half full. This he said was the cause of the problem and not having got 'dirty diesel'.

To clean out an existing problem Wurth Diesel Cure is recommended as a good choice.

Sometimes the third fuel filter is forgotten about.. Working from the engine back lets call the canister type filter no 1 filter, the next one back is the in line filter and the other filter is located in the fuel at the end of the fuel gauge sender.. Its a little gauze filter that becomes blocked up with Diesel crudge.. To get at it you will need to drop the fuel tank ( four bolts ) lower the tank under control using a trolley jack and disconnect the fuel flow and return pipes , two spade connectors for the fuel gauge and the breather pipe.( check this for blockage ).. The sender unit is now ready to come up and out of the tank (bayonet fit ) clean your gauze and reassemble.. Not as hard as it sounds.. All of the above applies to the benz 2.9 5 cylinder .. maybe worth a thought.

I have had problems in the fuel filter when putting veggie oil into the tank for driving on where it lifted all of the water and crap out of the bottom and associated condensate and pushed it to the fore. A couple of filters and it was fine to run.
Good luck with the job - it sounds cool and a weekends criac to lift out and replace at your lesiure