Fuel system schematics 99' E300

[EdzBenz]

Can anyone help me with the fuel schematics on a 1999 E300? Does anybody have any diagrams? I am having some problems with my greasecar system.
1. Engine is stalling 45 seconds after I switch to grease. The stalling symptoms are similar to running out of fuel. I remedy this by purging my lines and cranking the engine about 15 times while switched on diesel. Runs perfectly fine on diesel.
2. Diesel Fuel is being returned to my grease tank and is now overflowing.

Thanks for any help.

[Anthony Cerami]

Yes,
The two main lines are on the drivers side top firewall. They transition into rubber formed hoses. That would be the spot to plumb in the aux fuel system.
Not sure how you have it connected. One line is pressure and one is the return.
You may need some additional valving. Maybe your gulping air traped in the system when you switch over??
I would think you need to circulate or pressurize the grease like the dino fuel. Then introduce it to the engine via two small 3-way brass valves or "manifold" setup..... So your runing dino or grease but not both.
Sounds like the return is plumbed to the grease tank.

Of course dpending on the design you could also "blend" the fuels but only in warm weather.
Just my best guess........

[EdzBenz]

Anthony,
Thanks for the reply. I have plumbed my lines in that exact location. Maybe I have them switched around. Here's where I have both lines plumbed. Could you clarify this for me?
-Pressure- I believe the pressure hose leads underneath the intake manifold to the lift pump. This is where I have a fuel selection solenoid.
-Return- The return line comes off of the fuel filter which has two lines (one coming from injection pump, one coming from injectors) t'eed into it. This is where I have my fuel return solenoid.

I'm also having some trouble distinguishing what all of the lines leading to the fuel filter represent. Could you help me with this?

Any help would be appreciated. Thank you VERY much.

[Anthony Cerami]

Hi Ed,
I’m not really sure which one is the return. Reading your post again you have the pressure side in the grease tank. Since the return line has less pressure you are starving the engine when you switch over. I am thinking that the two fuel systems need to be isolated to work correctly. If I am thinking correctly.
I believe that the fuel system circulates all the time like a gasser.
However as the IP delivers fuel under high pressure the excess migrates back to the fuel tank via the very small return “looping” lines passing by the fuel filter and through the return line back to the firewall. The smaller of the two hoses at the firewall should be the return. Check the size of the rubber hose connected to the fuel filter. You will notice the looping return line connects there as well. That should be the other end of the return line going back to the firewall.