Soap tests
Why do we do it?
Soap can be seen as one of the three contributors to fuel system failures and faults. The other two are methanol still in the fuel and poorly converted fuel. There are two ways of testing:
- the 50/50 shake test
- a titrated test that will give a ppm (parts per million) result
50/50 shake test
The 50/50 test is relatively simple to perform.
Take a sample of dried, finished fuel, e.g. 50ml. Place it into a glass container and add 50ml of deionised water.( I suggest the use of deionised water because there have been concerns and odd results of shake tests due to the varying water quality throughout the UK.)
Then shake the living daylights out of it. This will create an emulsion between the water and the oil.
Allow it to stand. Within a few minutes you should see the fuel and water begin to split. When the fuel/water sample has fully separated you can then determine the results by a simple visual check. For a good pass, indicating little or no soap present, the emulsion should separate quickly (usually within 5 minutes) and the water layer should have the same crystal clear clarity it had before the test began. The fuel layer on top will now be cloudy. This is perfectly normal as the bio has taken on some of the moisture from the water.
- 50/50 water shake up test
Dried bio, 50ml cylinder, a mayo jar
50ml of bio and 50ml of water
Emulsion formed after shaking
Clear water after separation. Note that the bio layer is now wet and no longer clear
Assessing water clarity
There a few ways to assess the water clarity after a 50/50 test
- Hold it up to the light to look for milkyness
- See if you can read newsprint through it
- Shine a laser through it
Commercial particulate counters measure laser backscatter to assess particle levels. We can use a simple laser pointer to show up any soap particles in a similar way.
- Water clarity tests
The classic newsprint test - this sample has settled 24 hours in a warm location, so the bio layer has also cleared
Laser pointer test - visible beam in a sample known to contain about 250ppm soap
Laser pointer test - much better - a sample from the same batch but after passing through a dry wash tower
Titration test
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