Mercedes-Benz Forum banner

21 - 27 of 27 Posts

·
Registered
Mercedes Benz
Joined
·
1,754 Posts
Discussion Starter #21
confused-cius

So after 13 years of believing the D-Jet worked one way, as Graham and the Bosch Yellow Book (which I have) have proven,
I find out it works the opposite. The fuel pump does indeed feed the injector ring through the diaphragm then back to the tank
through the pressure regulator. The opposite of everything I had been taught. My apologies for the confusion.
Yes I was finding opposing literature from Dr. Djet on Oldtimer to the Bosch yellow book I'm reading. But it seems obvious to me that fuel is pushed through by the pump and the regulator, which is adjustable, sends back access through the return line but what isn't said is that is sent back at the same pressure as the fuel pump sends... which is one of the reasons having the proper fuel pump pressure is important- so that it doesn't blow the return line over time I am supposing. I'm sure the lines are made to handle far more than 2.1 bar (30psi). I've never seen a fuel line that isn't about 100 to 120 or more in capability. But I haven't seen everything and who knows what Jethro down the street put on his car.
 

·
Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
Joined
·
10,027 Posts
Y But it seems obvious to me that fuel is pushed through by the pump and the regulator, which is adjustable, sends back access through the return line but what isn't said is that is sent back at the same pressure as the fuel pump sends... which is one of the reasons having the proper fuel pump pressure is important- so that it doesn't blow the return line over time I am supposing. I'm sure the lines are made to handle far more than 2.1 bar (30psi). I've never seen a fuel line that isn't about 100 to 120 or more in capability.
Not sure if I understood what you meant, but the pressure in the return line between the regulator and the tank is very low - just enough to overcome the pressure drop through the return line and the mixing jet that is located inside the tank. Probably just 1 or 2 psi.

The fuel hoses themselves can take higher pressure, but a hose to pipe clamped joint has lower pressure capability. Not like the K-jet system that is hard piped.

The internal relief valve setting of the pump needs to be no higher than the maximum allowable working pressure of a clamped rubber hose to metal pipe joint. The original Djet pumps were hopefully designed that way. Bosch say the replacement pumps are also safe to use. But I would prefer an original or the Nissan. (I know - I keep saying that!)
 

·
Registered
Joined
·
16 Posts
Good morning, I ask permission to enter this subject. So the fuel comes from the tank, goes through the fuel pressure dumper (0280161002), follows the fuel pressure regulator (0280160007), which feeds the rail, and consequently the injectores and the bottom of the fuel pressure regulator, returns to the tank?
 

·
Registered
Mercedes Benz
Joined
·
1,754 Posts
Discussion Starter #25
From tank through filter screen ( locatated inside the fuel tank- on the bottom and requires a very large socket/wrench to remove) down to the "DAMPNER" to fuel pump- to fuel filter- to fuel accumulator- to engine. Excess fuel is returned to tank via the return line entering the left/ US driver side of the tank.
 

·
Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
Joined
·
10,027 Posts
From tank through filter screen ( locatated inside the fuel tank- on the bottom and requires a very large socket/wrench to remove) down to the "DAMPNER" to fuel pump- to fuel filter- to fuel accumulator- to engine. Excess fuel is returned to tank via the return line entering the left/ US driver side of the tank.
That would depend on whether Ortolani has a Djet (71-75) or a Kjet (76-80). There is no fuel accumulator on a Djet.

Quiet day here today, so here goes :):

On Djet,
Fuel goes from tank (through screen in internal swirl pot)
-->damper cage (1074700216 - This NOT 0280161002 ) ***see below
-->pump
-->filter
-->front of fuel rail on engine
--> splits to two sides
--> injectors.
-->excess fuel from rails combines at fuel pressure regulator (0280160007) and flows out of third nozzle
-->enters fuel damper. (0280161002 )
-->flows back to tank.
--inside tank it enters mixing venturi before entering swirl pot (tank screen is inside swirl pot)

*** The damper cage is no longer available. I did see one for early Djets on eBay.ca - https://www.ebay.ca/itm/MBZ-FUEL-DAMPER-2-CON-W107-EARLY-450SL-450SLC-W116-450SEL-450SE-MBZ-1074700216/153545015003?hash=item23bffefedb:g:j3MAAOSw1S9Wdi-j&vxp=mtr (Luckily they seldom need replacing. Just an empty can)

2611886

2611888


 

·
Registered
Joined
·
16 Posts
That would depend on whether Ortolani has a Djet (71-75) or a Kjet (76-80). There is no fuel accumulator on a Djet.

Quiet day here today, so here goes :):

On Djet,
Fuel goes from tank (through screen in internal swirl pot)
-->damper cage (1074700216 - This NOT 0280161002 ) ***see below
-->pump
-->filter
-->front of fuel rail on engine
--> splits to two sides
--> injectors.
-->excess fuel from rails combines at fuel pressure regulator (0280160007) and flows out of third nozzle
-->enters fuel damper. (0280161002 )
-->flows back to tank.
--inside tank it enters mixing venturi before entering swirl pot (tank screen is inside swirl pot)

*** The damper cage is no longer available. I did see one for early Djets on eBay.ca - https://www.ebay.ca/itm/MBZ-FUEL-DAMPER-2-CON-W107-EARLY-450SL-450SLC-W116-450SEL-450SE-MBZ-1074700216/153545015003?hash=item23bffefedb:g:j3MAAOSw1S9Wdi-j&vxp=mtr (Luckily they seldom need replacing. Just an empty can)

View attachment 2611886
View attachment 2611888

Over here cloudy and hot weather. Thank you very much MBGraham.
With this information it will be easy to assemble the fuel circuit. Greetings from Sao Paulo Brazil.


[/QUOTE]
 
21 - 27 of 27 Posts
Top