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Biodiesel/vegetable oil

Sticking pump system The boundary disc was stuck firmly to the trochoidal pump system. The pump system was removed for this picture – but its outlines can still be clearly recognised in the glutinous mass.
Sticking pump system The boundary disc was stuck firmly to the trochoidal pump system. The pump system was removed for this picture – but its outlines can still be clearly recognised in the glutinous mass.
In the past, RME (rapeseed methyl ester) was primarily used as “biodiesel”. Since November 2003, the new DIN EN 14214 standard for “fatty acid methyl ester” (FAME) came into force. In addition to RME, this also permits mixtures with other oils, e.g. soya oil, sunflower oil and used edible fats (animal fat, fish oil, etc.). Running on biodiesel can cause damages and malfunctions to occur sooner and more frequently than is the case with other (“fossil”) fuels [2].
 
  • In vehicles that have not been specifically approved to run on biodiesel by the manufacturer, seals and plastic parts in the fuel system can be adversely affected.
  • Biodiesel reacts hygroscopically; in other words, it absorbs water from the ambient air. As well as corrosion, this can lead to the growth of bacteria.
  • Oxidation takes place in biodiesel, which can cause fat molecules to flocculate, clogging filters and injection nozzles.
  • The good biodegradability of biodiesel comes hand in hand with poor ageing resistance. This can result in clogged filters through deposited particles.

Attention:
Biodiesel should only be used when the vehicle in question has been approved for this purpose by the vehicle manufacturer.
Damage caused by biodiesel In this case, after just 3 hours of operation, RME (rapeseed methyl ester) had disintegrated the carbon brushes forming an opaque, insulating layer on the commutator (“pole changer”) – the pump failed.
Damage caused by biodiesel In this case, after just 3 hours of operation, RME (rapeseed methyl ester) had disintegrated the carbon brushes forming an opaque, insulating layer on the commutator (“pole changer”) – the pump failed.
Quality management investigations at PIERBURG have revealed that when biodiesel is used, especially low-quality biofuels, the following malfunctions and damages can occur after just a brief period of operation:
  • Deposits clog filters and jam pump systems
  • Deposits have an insulating effect on commutators
  • Seals and plastic parts are adversely affected
  • Carbon brushes burn off after a short running time (“brush sparking”)
  • Corrosion destroys metal parts
View of the mounting of sliding contacts. The carbon brushes have completely disintegrated and form a coating on the pole changer
View of the mounting of sliding contacts. The carbon brushes have completely disintegrated and form a coating on the pole changer
Note - Attention | Motorservice Note:
“Brush sparking” refers to the formation of sparks on the commutator (pole changer) in electric motors. The carbon brushes provide the contact with the rotating part of the pump motor (rotor). In the brief moment when the carbon brushes short-circuit two blades with different charges, electrostatic discharges occur, which are visible as sparks. A coating on the glide path with an insulating effect generates increased discharges, which can cause the carbon brushes to burn off prematurely.
Sliding contacts at approx. 9,500 miles Left: Prematurely worn. Right: Normal condition at this mileage
Sliding contacts at approx. 9,500 miles Left: Prematurely worn. Right: Normal condition at this mileage
Destroyed glide path of pole changer Here, after the carbon brushes had burnt off, the springs that press the carbon brushes against the pole changer “gouged” their way into the glide path.
Destroyed glide path of pole changer Here, after the carbon brushes had burnt off, the springs that press the carbon brushes against the pole changer “gouged” their way into the glide path.
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