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Biodiesel conversion harms fuel-injector pump?

I’ve purchased a 1987 Mercedes-Benz, model 300 TD, V6 engine.

This car has been converted for duel-fuel use. It runs on petroleum-derived diesel fuel until it reaches operating temperature, then the fuel source is switched over to a separate tank with filtered fryer grease.

Fuel-injector pump Questions:

I need to rebuild/replace the existing pump because its output is inadequate – top speed of 45 mph going uphill.

1) I want to buy a used pump – isn’t there a “national junk yard network/parts registry” that junk yards use to find a specific (rare) part for a customer?

2) How can I avoid simply buying another defective fuel-injector pump? Look for one with low miles or ??

3) I could also have my pump rebuilt. How do I find a rebuilder with a reputation for top-quality work?

4) Is fuel-pump clogging (low output) a common problem with biodiesel conversions? Would an in-line filter protect the pump from damage? Do you know of a good web site to get answers to biodiesel-conversion questions?

Thank you! for anyone who provides some answers.

– Larry G., Seattle, WA

The fuel system in your vehicle was never designed to operate on used french fry grease, which is not biodiesel. Biodiesel is a refined product.

The french fry grease contains amino acids, and the seals in the injector pump and fuel injectors weren’t designed to be exposed to any kind of acid. So if you continue to use french fry grease as a fuel, not only will you be replacing the injector pump, but also the injectors from damaged seals from the amino acids.


i’m not sure, but i owned both a 1982 and a 1983 can have the injector pump checked for pressure. If it’s similar to the older model pumps there are two filters in that system. It could be the fuel pump, which runs off the injector pump. There are national dealers in both new and used parts, Goggle mercedes parts/used. The first poster is correct about the seals, there was great apprehention about low sulfer fuel.