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Fuel tank contaminated

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Black powdery substance in fuel tank

Hi,
There is a black powdery substance filling up on my cars fuel filters (`92 Mk1 Cti). It doesn't look like rust, im at a loss as to what this could be. Ive tried using injector cleaner but this stuff just keeps filling up. The engine cuts out under load. Is there any way i can clean the fuel tank without removing it? WP_20190121_002.jpg

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I'm not up on modern cars being a 92Cti, but is the fuel tank metal or plastic?

Do you still have the inspection hole on top of the fuel tank for the fuel gauge sender/lift pump underneath the rear seat?

You can hoover the tank out, make some sort of suction device with a filter so catch any bits, just do this in a very will ventilated area.

Have you checked your fuel filler neck for holes/rust?  

1988 Mk1 Golf GTi Cabriolet 1.8cc DX, K-jet. Daily drive. 300,000 miles and counting
1978 Mk1 Scirocco GLS 1.6cc FR, Webber carb. Weekend toy.

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Its essentially the same as a golf mk1 GTi although ive changed the engine to a 16v turbo; but the body is the same. It has the metal fuel injection type tank with the hole for fuel gauge sender. I like the hoover idea, will definitely give that a try. Filler neck has no holes/rust.
Should i treat the tank with any chemicals before i suck out all the dirt?
Thanks you for the advice.

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Fish around inside the fuel tank with a magnet on a stick get as much as you can out that way and keep cleaning the magnet, then either hoover it out or easy quick way is drop and leave the magnet in the fuel tank it will then collect and rusty bits when driving.
Hoover it out is the best way.

Try and keep fuel about 1/4 tank so you don't suck up the rubbish at the bottom and if you store the car over the winter fill the fuel tank up to stop rust/damp forming inside the tank.

Do you have the lift pump in the fuel tank, there should be a filter on the pick up to stop some bit's getting through?

lift pump like this.
VW GOLF JETTA MK1 CABRIO IN TANK FUEL LEVEL SENDER UNIT PETROL PUMP 867919051M | eBay


A bit more info on sucking the bits outs…
https://vwgolfmk1.org.uk/forum/index.php?page=topicview&id=how-to_2%2Ffuel-tank-cleaning_3

 

1988 Mk1 Golf GTi Cabriolet 1.8cc DX, K-jet. Daily drive. 300,000 miles and counting
1978 Mk1 Scirocco GLS 1.6cc FR, Webber carb. Weekend toy.

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No lift pump, just a fuel sender gauge. Thanks for all the advice; i will probably give it a shot in about a weeks time. I'll keep you posted. (i have a feeling the injectors might be blocked as well).

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I would first cut one of the older filters open and see if it is Metallic or rubber, that is does it move with a magnet.
If it doesn't then you are looking at rubber hose bits over internal tank issues.

You can try this if it is metallic.
Buy a large RARE Earth Magnet ( I have some I stripped out of a older full height disk drive, I use them to hold wood when I need a 3rd hand They are that strong.). DO NOT GET YOUR FINGERS BETWEEN TWO OF THE MAGNETS or METAL. If you bang them together they will break and shatter like glass.

Let it stick to the bottom if the tank for a few days and Jostle the tank.  I would place it in the Middle of the Center of the tank under the inspection or sender hole.  This would allow the metal to be all in one place easier to clean…

Rubber hoses can deteriorate and leave black res in the filters, metal can look black but under light is shiny and rusty colored.

Knowing which helps you.


What do Divorces, Great Coffee, and Car Electrics all have in common?

They all start with GOOD Grounds.

Where are my DIY Links?

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Now if you have to drop the tank, to have it cleaned or replaced,  then you have to lower your rear axle, it is best to start cleaning the studs of debris and rust, then spray them every day with a penetrating oil ie: Kroil, PB-Blaster not WD-40.  When removing the bolts use an impact wrench, a breaker bar and socket with an extension will tend to Torque Shear those nuts and Studs off cleanly leaving you in a bind.

Be mindful of the Rubber Rear Brake Hoses as they can be brittle and break or internally get damaged and it wouldn't hurt you to replace them as they are easier to remove with the axle lowered.


What do Divorces, Great Coffee, and Car Electrics all have in common?

They all start with GOOD Grounds.

Where are my DIY Links?

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Hi there Briano,

Its non metallic and i think you are right about it being rubber. Now that i think of it, i did have a few fuel pipes burst in the engine bay when the fuel mix has race fuel and toluene added to it. This stuff seems to really destroy the rubber fuel pipes if left to stand for awhile. I am NOT in the mood to remove the rear axle. Thanks for pointing me in the right direction.

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The advent of E-10 or E-15 petrol mix over here tears up the older not ethanol rated hoses.  I found that when I removed my fuel filter when I bought my car, and found that one side drained out clear brownish on one side and the other was black clear which told me my hoses are going bad internally.

I replaced them all with e-15 rated hoses, and on my 92 when I converted it to a single fuel pump in-tank it was
evident when I removed all the old hoses that they were way beyond shelf life.

Toluene is a rubber eater. It really doesn't like certain blends of rubber… so I would suspect that you are correct that the hoses are being Dissolved in bits that you are seeing in the filters.

Once this condition starts, you can't stop it so replacing the rubber bits is the only thing you can do.


What do Divorces, Great Coffee, and Car Electrics all have in common?

They all start with GOOD Grounds.

Where are my DIY Links?

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if its a gti tank then they have a swirl pot inside with a rubber diaphragm to keep the fuel in it, could be that breaking down.
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