Stops running after 5 mins

[brucegtx]

Recently bought an 84 gtx after 20 years of being scorocco less. Had a few issues as had been standing for 16 years in a garage. Replaced a few sections of fuel pipe, cleaned up the swirl pot accumulator and pump along with a few other bits of brake pipe.
All looking good and passed the mot then boom! All of a sudden she started to chug when you put your foot down and got worse. It then ran for a minute and went lumpy the cut out.
Changed fuel filter and looked like coffee! Put new one on, new air filter, plugs, ignition amp, fuel pump relay injector seals and coil£££££ but still conks out after about 5 mins of running.
Set fuel mixture to about 4. Only other thing to do is the tank. Ther is sludge in the bottom of the tank.
I see this is a common fault with roccos, is this likely to be the problem? Or something else?
Any advice would be greeaat!
New on the register and in Mansfield notts.
Bruce

[ianaudia4]

You have all the symptoms of crap in the tank! Is the filler neck goosed?
You may find you will need to change the fuel filter again!

[mark1gls]

If the fuel looks like coffee there is alot of crap somewhere in the fuel system. Check the lift pump in the fuel tank there is a mesh filter on the end which could also be blocked
Does the other fuel pump under the car get louder when the car judders and runs lumpy?

[the edmundator]

I agree that your filler neck and/or tank are rotten. If you're planning on keeping the car, replacing both would be the easiest way to solve this. New tanks are available and not horrendously expensive (given that they will last at least 20 years even if neglected) and you can get new filler necks from VW classic parts (provided you have a space saver spare wheel). To clean the tank properly you'll have to remove it anyway.

[brucegtx]

Thanks folksIi think the tanks ok, and i thought the filler was as it seemed solid, however its probably caked up inside. Looks like a new filler neck them as it has the space saver. Defo keeping it as been looking for this one for years and is an original minter.
Will a magnet work as a temp measure to see if it is crap in the tank?

[Tim_R]

If the fuel is coming through brown then its contaminated with fine bits of rust and possibly water. You really don't want that getting into the metering head and injectors as it'll clog up the fine holes in the metering head and screw up the spray pattern on the injectors.
It's worth lifting the back seat to get to the fuel gauge sender and lift pump, remove them and have a look in the tank, if the inside of that has gone rusty all you can really do is change it. If its shiny bright metal then drain the tank and flush it out and have a really good look at the filler neck.

[brucegtx]

Thanks Tim, gonna remove tank and filler neck. hopefully this will sort it.

[the edmundator]

If it's spent 16 years in a garage with air (and therefore moisture) in the tank, I'd be surprised if it didn't at least have a good coating of surface corrosion inside.