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From digest.v4.n749 Wed Jun 19 22:36:44 1996
From: Andrew West <>
Date: Thu, 20 Jun 1996 10:59:32 +1000
Subject: <E30> Water in Fuel?

In V4 #746, Chris Smith asked how to tell if there is water in the fuel tank.

  1. Get a fuel can full of fuel to put back into the car when you are finished.
  2. Drive until the tank is almost empty (reserve light comes on, then another

    20 miles or so)

  3. Park on a level surface, then raise the left hand side of the car evenly

    (front and rear) as far as is reasonably possible. This lets the fuel settle to the right hand side of the tank, where the drain plug is.

  4. Put a large-mouthed non-plastic container under the drain plug. A glass

    container makes step 8 easier.

  5. Touch the car and the floor at the same time to drain any potential

    static charge on your body or the car (sparks are bad around fuel)

  6. Lossen and carefully remove the drain plug (6mm allan key required)
  7. Let some fluid drain into the container, and pop the plug back in.
  8. Check what you drained out. If it is clear (ie not cloudy and does

    not contain a lot of suspended matter, eg: rust particles), check that it is fuel and not water! If it is pure, clear fuel, you have no problems. If it is clear water you are lying. If it is cloudy this indicates some water suspended in the fuel. If this is allowed to stand long enough it will separate into two layers. If there is rust, you have or have had water in the tank. If it is bad, you may need to remove the tank and have it steam cleaned.

  9. If there is some water in the tank, drain the tank completely, add the

    clean fuel and some alcohol (I have been told that isopropyl alcohol is the best for absorbing water). You will need to replace the fuel filter (in the engine bay), and might need to have the fuel system overhauled to clean it out completely. Keep adding the alcohol to the tank for a few fills to clear up any remnants of water. The water may cause the fuel pumps to wear quickly and may cause failure of the fuel pressure regulator/pressure reservoir.

I would advise everyone to check this regularly (eg once a year), as I have been caught out. My E30 was running pretty badly and I found about 1.5 litres of rusty water in the tank. Eventually I had to replace the tank, pumps and have the injection system overhauled before it was back to normal.

Andrew West, '83 E30 318i, BMW Club Queensland

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