DD fuel systems

[Bob Gil]

Ok Lets see if I understand this right.

Sorry if I am a little slow but these DD are a lot different than I have messed with in the past and I want to make sure I get it right the first time.

The fuel comes from the tank thru the primary filter.  Then to the fuel pump on the engine that pumps it thru the racks on both heads and then the fuel goes back thru the secondary filter (filtering out any thing it might have picked up going thru the racks?) then back to the pump again.

I am use to the lines going from the pump to each injector with it's own line.  Macks are little different.

[Dallas]

nope, the fuel comes from the tank, passes through the primary filter and possibly through the secondary filter, then into the RH head, then from there to the LH head then Normally through the secondary filter, then back to the fuel tank.

Fuel does NOT return to the pump from the heads. YOu will shortly have a lot of injector failures if you do it that way. The fuel is used to cool the heads and the injectors and if it can't get back to the tank, just gets hotter and hotter.

Good Luck!

[Bob Gil]

Ok I will have to locate the return line to the tank.  Mine is set up to go back to the pump on the engine.

Looks like I need to fine out more on it before I go to the shop to get lines made.

[TomC]

On mine the fuel line comes from the tank, goes through a one way check valve to the primary filter, then to the fuel pump, then to the secondary filter that has the fuel pressure switch to turn off the starter when the fuel pressure gets above 10psi, then into the right head in the rear-through feeding the right head injectors to the front & crosses the front right to the front left head that feeds the left head injectors.  The return line goes from the front of the left head over to the front right head, exits out the rear of the right head and back to the fuel tank.  Good Luck, TomC

[Bob Gil]

Tom I have looked at the pictures I have of mine and I think you are right I got the oil line mixed up with the fuel lines.

In the pictures you can see the line that goes from the cross over line betwee the heads and goes to the rear.

In the other picture you can see where it attaches to the other line that comes out of the back of the second head. 

I wonder what keeps the fuel from bypassing the second head all together?

This also answeres the problem that was puzzling me.  As we drove the bus we used fuel out of the can in the engine compartment but the main fuel tank on the right side of the bus was trying to over flow.  I guess it was going back to the tank after all.

[makemineatwostroke]

Bob,you do need to get you a DD Engine manual it will make life so much easier for you. Tom C has the most common hook up but most DD have a fuel return from the left head only

[Bob Gil]

I am looking for one of the manuals on E-bay as we speak.

I hope it will help. 

[gus]

My 671 is the same as TomC's without the pressure switches.

Makes no sense to me to go through the heads before the secondary filter??

Also on the 671 it is suction to the mechanical fuel pump on the engine. I think I've read posts that some have a pressure system with a pump at the tank.

Myn '94 Dodge Cummins PU has the same suction system. Newer ones have electric pressure systems.