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Biodiesel Usage: Our Experience and Precautions

Biodiesel Contaminants on VW Fuel Sending Unit

Gear case (3)Understand that our mission is to advise our customers based on our knowledge and experience about biodiesel usage. Karmakanix is not here to rag on fuel manufacturers, whether they be large companies or individuals. Nor are we making any recommendation about whether a customer should use biodiesel or not. That said, this is what we see when we open a fuel tank or a pump on a vehicles that has had exposure to contaminated biodiesel, and/or fuel that did not meet the ASTM standards for biodiesel.

 Clogged Fuel Filters and Check Valves

We regularly include fuel restriction tests before and after fuel filter replacement in our diagnostic procedures. These tests will reveal restriction issues from contaminants in the fuel filter, fuel tank and in the tiny check valves of the fuel sender. And we often identify the problem before it causes power loss, break downs or extreme fuel pump damage. Often we end up removing the fuel sending unit from the fuel tank to inspect the sender valves and the bottom of the fuel tank. It is our policy to check perform restriction tests and check inside the tank every time we replace a fuel pump on a car running biodiesel. We end up replacing the fuel sending unit way more than half the time, as the contaminates and clogged valves contributed to the fuel pump failure, and likely would cause the new pump to fail. Pump damage from restriction usually results from cavitation, and lack of lubrication and cooling.

Biodiesel Manufacture: The Leftover Methanol

Methanol contamination is a really really bad problem. We have seen a Rabbit Pickup with the entire plastic windage tray inside the fuel tank melted into a gooey blob. We have seen customers who needed fresh injector return hoses every year. We have seen a motor that started leaking from the fuel pump front seal so rapidly, that the timing belt got washed in biodiesel and broke within 100 miles, bending all the valves. Those days are pretty much gone. A few farmers are out there making home brew that is melting their plastic filter housings. But almost everyone now uses quality biodiesel from reliable manufacturers. And that fuel has no appreciable methanol content.

Glycerine Leftovers

Generally, we do not see any real damage from glycerine with quality biodiesel usage. We have seen some problems: Once we opened a fuel tank in a Golf PD Tdi to find the fuel had turned to Jello, thank some mad scientist in Texas. Another Tdi Jetta had what looked like carrot juice and cottage cheese, which was glycerin plus rust. There have been a few other minor occurrences of glycerine contamination, but just from the home brew crowd.

Mixing Different Biofuels, and Iffy Additives

We have had issues with biodiesel when combined with some “recommended” fuel additive. The interactions are mostly due to the ingredients that created acids. One customer filled up out of town at a reputable biodiesel station, and had about a 4 gallons of her local fuel still in the tank. As a precaution, she added a small amount of a fuel additive that we had never seen or heard of before. The resultant instant corrosion froze the pump within hours. The first rebuilt pump we installed went 30 minutes before it too began to freeze and throw a diagnostic trouble code DTC for the quantity adjuster. We at first thought the rebuilt pump could be at fault, although our rebuilder rarely makes any booboos. We did check the fuel quality and the fuel tank, and found the fuel to look and smell normal. But evidently we did not have the proper chemistry set to detect the anomaly. Another pump was installed, but before it got terminally damaged, the rebuilder called to inform us that the first rebuilt pump was full of rust. In 30 minutes. It turned out to be severe corrosion from extremely high acid and alcohol content. We know biodiesel to be compatible with Redline, Amsoil and Stanadyne diesel fuel treatments. Please do NOT pour anything in your biodiesel tank that you are not sure of its compatibility with biodiesel.

Biodiesel Inside Engine Wiring Harness

This topic needs its own section because the etiology of the issue is unclear. But it is worth mentioning as we get about one case per year where we diagnose a running problem to be caused by biodiesel that has gotten inside the engine wiring harness. How the biodiesel gets into the wiring harness varies with the type of fuel system. Vehicles up through 2003 have an external pump that feeds externally mounted injectors. The fuel could be getting in from either the fuel pump itself or from the sensor mounted on the number 3 injector. With the Pump Duse engines that start in 2004, the fuel is most likely getting in through the fuel temperature sensor. One might think that fuel pressure may be involved, but the PD fuel temperature sensor is on the fuel return side of the engine and has no fuel pressure to speak of. The contamination wicks through the system like a capillary action. Although it is made from oils, biodiesel is actually quite conductive, especially as it gets old. The problems are varied, ranging from filling up solenoids for the boost control and EGR until they jam, to shorting out other sensors and the ECU (Engine Control Unit). One car went so long that the biodiesel made it through the fusebox and was coming out through the headlight wiring. We are unsure if the acid content of old biofuel started the problems, or if methanol was involved. Although theses problems are rare, they emphasize the need to heed cautions about using quality biodiesel, and not letting the fuel get much more than two months old.

When Water Is Not Your Friend

Let’s just mention that the ASTM standard for water and sediment is .050%, and start there. Water content used to be a really big problem in regular petroleum diesel back in the 80’s. Water was getting in the gas and diesel fuel mostly from filling stations with cast iron tanks. Water would either ingress right through the cast iron walls, or leak through the seals on the tank caps. Sometimes condensation from low levels of fuel in the storage tanks at the filling station for long periods plagued car owners as well. Sometimes a car would get towed in with a half gallon of water in the tank.

Water in the fuel is clearly the leading cause of almost all fuel related failures, both with regular petroleum diesel and biodiesel. There is more water present in Northern California biodiesel that is generated from recycled oils than the Midwest version of biodiesel made from GMO soybean oil. The cooking process causes some water to be bound to the oils that cannot be removed during the drying process. Additionally, and of more consequence, biodiesel is hygroscopic and will slowly pull water out of the air. Since water is involved in most organic reactions and growth cycles, chemical changes and contaminants result from the water in the fuel. Chemical changes and microbial growth in the fuel lead to the large amounts of deposits that we commonly find in the fuel tanks and filters of cars that have run on fuel that is too old. Most times, there are similar deposits in the fuel pump and injectors. The contaminants may have been formed after the fuel filter, or the filter paper could have been damaged by microbes. These contaminants are responsible for most of the fuel pump and motor failures that we find on diesel cars.

Shown are pictures of injectors from a 2004 Jetta with a Pump Duse (PD) engine. The vehicle was run on a tank of fuel that had been topped off with a 5 gallon jerry can of biodiesel that was two plus years old. The acids that had formed from the water content caused enough corrosion to render the car undriveable within weeks. The symptoms included stalling when coming to a halt, 10 – 15 seconds of cranking to restart, and stalling on the freeway when the throttle was released. The entire fuel system had to be replaced.

Gear case (2)Karmakanix Knowledgebase on Diesel Engine Damage from Water

Gear case (2)Karmakanix Knowledgebase on Successful Use of Biodiesel

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