Interesting Article from the Science in Africa Newsletter
Helping Biodiesel become unstuck By Dr Garth Cambray
Clogged arteries are a bad thing in a human heart, and clogged pipes are a bad thing in the heart of a diesel engine - the injector pump. Oxidative damage to biodiesel oils leads to varnish formation which can stop an injector pump permanently. In this article we explain how you can repair such a pump, and take measures to prevent this happening in the future.
Biodiesel is a very topical fuel at the moment, with many in favour and many against its use. Biodiesel made from waste fats and vegetable oils is generally agreed to be a responsible way of disposing of these wastes through combustion in an engine. The damage which fats undergo as a result of the cooking process prior to being discarded as waste does however change the nature of the resulting biodiesel. Given that most operations which use waste fats and vegetable oils to make biodiesel are small operations distributed around the globe, little attention is paid to the problems encountered in the use of these small scale biodiesel products.
Talking to a number of producers I have noticed that many have mentioned a problem with Ford diesel tractors where the injector pump, a rather expensive piece of equipment, becomes clogged with varnish/lacquer like gums which stop the pump working. In all cases mentioned I was told that the pump was irreparable and had to be replaced at considerable cost. While running experiments with ostrich biodiesel on a tractor in Grahamstown we had a similar problem. Upon disassembly the pump was entirely coated in a thin black layer of sticky gum. All the finely tuned parts of the injector pump were unable to move freely and as a result the pump did not work at all.
This posed an interesting challenge - to find a way of cleaning the deposit to restore the functionality of the pump, and to find an additive to stop the deposit reforming. The solution needed to be one that would be universally relevant, hence the ACDelco range of products distributed by the global company, GM, was selected. A number of cleaners, fuel treatments and sprays were selected.
Individual gummed components were treated with different liquids to ascertain if these would remove the deposit. The ACDelco Carburetor Cleaner, which contains a mixture of acetone, xylene and methanol instantly removes all the deposits from the pump. While cleaning, we initially removed the gums and varnishes and then rapidly rinsed the parts with biodiesel to remove the residues of the Carburetor Cleaner so that this would not have a chance to damage seals and gaskets. Note that the cleaner contains methanol, which passes through the skin and causes damage to the liver, hence it is prudent to wear gloves.
It was found that soaking parts overnight in the ACDelco diesel fuel treatment, (containing a Stoddard solvent, petroleum distillates and the mysteriously named hydrotreated light, which is in fact an oil) removed deposits as well, although somewhat more slowly. Hence, this additive was added at the rate of 10ml/l of biodiesel as recommended by the manufacturers. The volume of fuel that had been used previously before the pump ceased to work was ascertained and after the same volume of treated fuel had passed through the repaired pump it was inspected and found to have no deposits forming.
Hence it is reasonable to conclude that treatment of an injector pump which has been stopped by gumming with degraded biodiesel components using a solvent containing acetone, xylene and methanol, followed by treatment of biodiesel with a fuel treatment containing Stoddard solvent, petroleum distillates and hydrotreated light oil will solve the problem of injector pump gumming.
This is very useful information for all small scale biodiesel producers who, should they encounter this problem can now fix an injector pump, or better still, preempt its malfunction through adding diesel fuel treatment.