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Last night I ran through the entire ignition system of my 1985 Mk1 Golf Cabriolet 1.6 (Carb) Auto and managed to get a nice strong healthy spark. This allowed me to start the car on Easy Start because I currently have the fuel lines disconnected. The reason the fuel lines are disconnected? My fuel tank is full of rust.

The source of the rust was corrosion in the fuel filler neck which I have previously replaced. The fuel filler is mounted just above the rear wheel so years worth of spray from the road, mud and rust particles are now sitting at the bottom of my fuel tank.

Removing the rust from the bottom of the fuel tank on one of these cars is usually a really easy job. Under the rear seat is an access hatch which you simply unscrew. Unfortunately, it seems that someone has been here before me and they've broken the access hatch and then bonded it to the fuel tank.

It is possible to remove the fuel tank but that means removing the exhaust system, disconnecting the brake lines and dropping the rear beam. Amongst other things, this includes removing nuts from captive bolts that are welded into the rear monocoque of the car and these are prone to snapping, a scenario that I would like to avoid for obvious reasons.

When the car was on the road I had to clear the fuel lines by blowing them through with the filler cap removed at regular intervals (initially every 10 to 20 miles, although that did improve with use). This combined with buying bulk inline fuel filters and using them as sacrificial items. I've also reached the point where I can rebuild a Pierburg carburettor with my eyes closed.

I really want to use the car as regular transport and have reached the conclusion that I have no option but to do something to clear out the fuel tank. If it helps, the fuel tank is steel and other than containing silt, is in very good condition.

Does anyone have any idea as to how I can clear it out without removing it from the car? I have a number of ideas myself but wondered if anyone had any proven suggestions.

UPDATE: For anyone interested in what the fuel filler neck looked like, here is me taking it off the car: https://www.youtube.com/watch?v=WcjJ1Xfl-us

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    It seems like it would be worth fixing the access hatch to me.
    – GdD
    Nov 30, 2018 at 15:42
  • I really do think I’m going to have to bite that bullet.
    – Steve Matthews
    Nov 30, 2018 at 21:23

2 Answers 2

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Given what you've said, I'm assuming the rust is in the form of small, dry flakes and dirt. Is the tank fully dry, or is there still some fuel or other liquid in there? If it's dry, you might be able to do something by removing the filler neck and inserting a vacuum hose to suck the loose debris out?

Looking at photos on the internet, it looks like there's a largish outlet at the bottom of the tank - you could use this to flush it out?

You'd then need to rust-proof the tank - there are various products out there that do this, but usually you pour them in, swill them round, then pour out the remains - difficult if the tank is still in the car.

Personally, I'd replace the tank, just for peace of mind - the last think you want is the tank rusting through and leaking fuel under the car, and there's no real way to know for sure how much the inside of the tank has corroded, especially if it's been empty for a while. You can get new ones online for £90, which is less than two tank-fulls of fuel at current UK prices...

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    I concur with your last ... replacement is most likely the easiest and best option. Especially for peace of mind.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Nov 30, 2018 at 13:03
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    There is still fuel in the tank. The condition of the tank is very good. The idea of using the large outlet to effectively "swill" the tank. The rust in indeed in the form of small particles, most of them around the size of the main jet of the carburettor! Replacement is an option but I fear snapping an axle bolt and having to cut and weld the box section of the chassis.
    – Steve Matthews
    Nov 30, 2018 at 14:19
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Why was the fuel filler letting in so much road dirt? Did it have a hole? They are usually blessed with a fuel cap...

However, I would suggest what you can do is to put a large fuel filter in the fuel supply line close to the tank, but make it easy to replace. This will stop the dirt progressing through the system, and if large enough it won't need changing frequently.

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  • 80's VWs had a steel pipe from the filler to the tank, which ran through the wheelarch - the mud, salt etc flung up by the wheel trapped moisture against the pipe, creating a rust-trap and causing that pipe to rot out.
    – Nick C ♦
    Nov 30, 2018 at 13:16
  • @NickC lots of vehicles had that - landrovers as well... but it was usually obious there was a problem as the fuel leaks out rapidly...
    – Solar Mike
    Nov 30, 2018 at 13:18
  • It depends where on the pipe has rusted through - if it's above the level of the tank, such a leak might not be obvious
    – Nick C ♦
    Nov 30, 2018 at 13:20
  • The filler neck was rusted through completely right at the top of the pipe, just behind the filler cap. It was like that when I bought the car but the price was too good to walk away.
    – Steve Matthews
    Nov 30, 2018 at 13:34
  • Looking at a tank or a filter then - assuming you have sorted the filler... should be good when it's done.
    – Solar Mike
    Nov 30, 2018 at 13:42

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