Help..Diesel MB. high school, metal shop project car - PeachParts Mercedes-Benz Forum

oregonbarn · #1 04-04-2007, 11:12 PM

I have been reading from this form for a bit now and the knowledge base seems to be unlimited about the diesel MB. I teach at a high school, metal shop, but we do lots of other areas including a veggie conversion on an 83 300SD. We made the tank, installed the heated filter and ran the hot water and veggie lines to the trunk. For the last 3 days we have been trying to get the air out of the diesel system so we can start the engine and finish the conversion. I have been pumping with the hand pump and it seems that air is getting into the system around the diesel filter. We have used fuel injector type hose clamps and a new filter, but after pumping for minutes the diesel just will not get the air out and when you stop pumping the fuel will retreat back toward the tank. We have the clear pvc lines and can see the flow. Any ideas or suggestions will be greatly appreciated.

whunter · #2 04-05-2007, 05:52 AM

Pictures will help with this conversion diagnosis.
We need a fuel flow schematic/drawing.

For greater technical help, I moved your post from my "Biodiesel and WVO - SVO links thread".

Please bookmark the following thread:

http://www.peachparts.com/shopforum/showthread.php?t=142446

***************************************

Special attention to these topics:

Diesel Injection
Engine Electrical
Engine Mechanical
Fuel Delivery

Have a great day.

mespe · #3 04-05-2007, 06:25 AM

You obviously have a fuel leak somewhere. Fuel should flow into the primary filter due to gravity. Could be blocked tank strainer that prevents the fuel from flowing like it should. When you pump you are creating a vacuum and pulling some fuel, when you stop, the vacuum pulls the fuel back.

Maybe take the car to the automotive classroom and have them diagnos the problem. Also has the car been started and driven BEFORE the conversion?

Good luck

rebreath · #4 04-05-2007, 07:36 AM

Quote:

Originally Posted by oregonbarn

I have been reading from this form for a bit now and the knowledge base seems to be unlimited about the diesel MB. I teach at a high school, metal shop, but we do lots of other areas including a veggie conversion on an 83 300SD. We made the tank, installed the heated filter and ran the hot water and veggie lines to the trunk. For the last 3 days we have been trying to get the air out of the diesel system so we can start the engine and finish the conversion. I have been pumping with the hand pump and it seems that air is getting into the system around the diesel filter. We have used fuel injector type hose clamps and a new filter, but after pumping for minutes the diesel just will not get the air out and when you stop pumping the fuel will retreat back toward the tank. We have the clear pvc lines and can see the flow. Any ideas or suggestions will be greatly appreciated.

replace the pump!it sounds like it is leaking.they are cheap.

Jim Wickham · #5 04-05-2007, 08:29 AM

is the tank vented propperly? If this is the tank you built make sure you have a vented cap on it. I would think without a vent you would be creating a vacuum in the tank when you try to pump and that would cause the fuel to retreat when you stopped pumping.

oregonbarn · #6 04-05-2007, 11:04 AM

The tank we built was for the veggie oil and it has not even been used as yet, because the car will not run on the diesel fuel. I will have a kid make up a diagram to post so you guys can see the route for the fuel. We have 2 three way values to change from diesel after the veggie is heated. The pump was changed to pull the diesel through the diesel filter and then into to first value that would switch from diesel to veggie. It goes then through the pump into the injector assembly. The air must be getting into the diesel system somewhere before the pump. I had a owner of the same type of 300, running veggie and copied his route. He said to replace the stock pump, because it is usually not working well after all these years. We will take some pics and make the diagram asap. Thanks so much for the help.

Barney

whunter · #7 04-05-2007, 11:16 AM

Quote:

Originally Posted by oregonbarn

The tank we built was for the veggie oil and it has not even been used as yet, because the car will not run on the diesel fuel. I will have a kid make up a diagram to post so you guys can see the route for the fuel. We have 2 three way values to change from diesel after the veggie is heated. The pump was changed to pull the diesel through the diesel filter and then into to first value that would switch from diesel to veggie. It goes then through the pump into the injector assembly. The air must be getting into the diesel system somewhere before the pump. I had a owner of the same type of 300, running veggie and copied his route. He said to replace the stock pump, because it is usually not working well after all these years. We will take some pics and make the diagram asap. Thanks so much for the help.

Barney

Please call me Barney.

D2010-268357
Diesel Primer Pump Bosch IN STOCK $28.91
http://catalog.worldpac.com/mercedesshop/sophio/quote.jsp?header=header.jsp&footer=&product=D2010-268357&partner=mercedesshop&baseurl=http://catalog.peachparts.com/&clientid=catalog.mercedesshop

Have a great day.

Addicted · #8 04-05-2007, 11:54 AM

Hey Barney,

Funny I see you here. I've been off and on this forum but been busy with work and deployments lately. Yeah if I remember right we tried priming your car with the hood up that day and some fuel was leaking around the edges. It is a pretty darn good bet that is where it is comming from. Which one of those diagrams did you use again? But anyway for about 10 bucks and 5 minutes you can easily find out if it is that pump.

Go ahead and PM me or e-mail me at jasontraylor@gmail.com. Not sure if I updated my e-mail on this forum yet.

Sounds like you couldn't get the 74 240D running. Anyway let me know or give me a call at 503.544.7312 would love to hear how the project is going.

DeliveryValve · #9 04-05-2007, 12:25 PM

Quote:

Originally Posted by oregonbarn

...... I have been pumping with the hand pump and it seems that air is getting into the system around the diesel filter..... Any ideas or suggestions will be greatly appreciated.

I wouldn't use the hand pump to get the veggie fuel through the filter, in my setup I could pump all day and still get no oil even though the hand pump is basically brand new. What I have done before is remove the outgoing line from the veggie filter and hook up a Mity Vac with the bleeder bottle attached. This provides a much greater suction to move the oil. Once you fill the bleeder bottle and determine in fact there are no leaks, reattach the line and you can use the Hand pump to finish the job.

Good Luck

SD Blue · #10 04-05-2007, 12:38 PM

I'm assuming that one 3-way valve is for fuel input and the other is for the return?

Double check that both of the 3-way valves are switching completely. It sounds as if the return line may be blocked and causing pressure to build in the system.