If this post is not appropriate for this forum please advise and accept my appology.

I live in a rural area without much in the way of automotive technical resources. A neigbor of mine had her 1979 MBZ 300D converted to bio-diesel and now it does not run. It has not run since December. She has had the injectors nozzles, the glow plugs and the GP relay checked and also converted it back to petro diesel. It still does not run. No one for a long long ways away has ever seen a Mercedes Benz diesel engine. So, I am looking for thoughts on this problem on line. If it is not a stretch to discuss a different make of engine on this forum, I appreciate any replies. Perhaps the problems with this engine are applicable to International diesel engines that are converted to bio-diesel.

 

You convert an engine to run SVO (straight veg oil), but no conversion is necessary for biodiesel. (Other than making sure fuel lines are bio compatible). To be clear, SVO is not biodiesel.

 

binuya is exactly right. Diesel engines require nothing "changed" to run biodiesel. If they are running unheated veggie oil the problem could be several things. Injector pumps will not tolerate unheated SVO for very long, and using unheated SVO will cause a buildup BEHIND the piston rings and cause the cylinders to wear excessively with a resulting loss in compression. More information is needed........

 

My mistake, it was a Lovecraft Veggie oil system. I will ask her if that included a fuel heating component. Are there any other questions I should ask? She wants to sell this car and I am giving it some consideration but would like to know more. With petro diesels, I would think an oil analysis would be appropraite. Is that meaningful with a car that ran on vegetable oil? Does veg oil dilute mineral based lubricating oil?

If unheated veg oil results in cylinder deposits and excessive wear do leak down tests mean anything. While I have a 7.3 International diesel in a truck and a Cummins in a tractor, I am not very knowledgable about diesel engines.

How would a fuel heater work? Is it anything like the heat exchanger on older LPG powered trucks? Winter here is very cold- double digit below zero... farenheit.

 

If it happens to be this one: Lovecraft Biofuels - 77 to 85 Mercedes Benz conversion kit

you probably won't be happy and neither will she.

The ONLY way you can use veggie oil is with a Good quality TWO tank system. You have to start the engine on reg diesel. Then when the engine gets warm enough to warm the in-tank heater, the hose in hose lines are warm and the filter heater,THEN you can switch to veggie. When you want to stop the engine you must do the opposite, and switch over to reg diesel to purge the fuel system.

Unheated veg oil has a much greater viscosity than diesel and can cause injector pump failure. Ever notice how veg oils and grease's form a hard carbon on your back yard grill? When you burn UNHEATED veggie oil in a combustion chamber these unburned gasses build up behind the rings and wear the cylinders out. I've torn down two engines with the same complaint and one of them had over .020 wear!

Do a compression test first. If the compression test looks OK, pull an injector line and an injector off and crank the engine while looking for fuel spray. That should let you know whether it's just the IP, or internal........

 

What an *** pain. That is too much driver involvement for most women. It is too much driver involvement for most men. Monitoring temp guages, flipping switches, opening and closing valves both at start and when finished with engine. Shoot, why not just hire an engineering officer to ride in the engine compartment and put a ship's telegraph where the gear shifter was located?

Thanks for the info, I will relay it, that is if she is still communicating with me.

 

Think this quote needs to be saved somewhere ...Sticky note?... The subject seems to come up alot. Explains things in terms I think everyone can relate too (grill analogy). Never thought of it that way myself. Thanks yet again Don. l

 

No problem Trent!