My guess, since it's at the highest point, it is for constant air bleed to the tank..

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

It is also possible that an "air lock" could occur if this orifice did not exist.

Just like the air lock preventer on the waste line of your dishwasher.

There is a pressure differential across this orifice - pump pressure (7psi) on lower side and return pressure (atmospheric pressure) on the top side.

Henceforth we should change the name of the "three-way banjo" to "THE FOUR WAY BANJO SECONDARY FUEL FILTER HEAD CONNECTOR......."

Any objectors?????

I studied the OM603 manual for some info. This connection is referred to as a "choke orifice" and it's .8mm (.031") in diameter.

Purpose is not stated.

This miniscule diameter tells me that the Designer had to put it there for air/vapor venting and not for liquid flow. My guess is that it is to prevent vapor lock. It can also facilitate venting as Funola states from the highest point in the circuit. The other reason I gave which is prevention of lift pump dead heading is probably not valid.

The orifice size is small enough to obviate the necessity for a check valve.

I have learned something today which makes me feel good


Now since Funola owns this thread is he content that every issue has been addressed????

Does the 603 use the same filter head as the 616? Anyone know the purpose of the "choke orifice"?

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I do not own this thread. I merely started it because I needed help, and I learned a few things in the process. We all did. That's the great thing about this forum. Where else can you post a question for help and get a reply in less than 5 minutes? As far as has every issue been addressed? I'd say no. I still like to find out why I was not able to bleed the system using the normal factory procedure.

Come to think of it. The bolt that goes into this 3 way banjo is the one that the veggie conversions have to plug in order not to feed VO into the diesel filter. Maybe part of the purpose of that orifice is diesel fuel heating for cold weather?

Quote:
"I have learned something today which makes me feel good


Now since Funola owns this thread is he content that every issue has been addressed????"

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Hi,
Had a similar problem, my 87 300D turbo would not start after three months jacked up in the front. I removed the return line from the secondary filter housing and the supply line. Jammed some compressed air into the return, heard gurgling in the tank and then a gush of fuel from the supply. Stopped the flow with my finger, reattached both hose and the car starred immediately. Did this after numerous starting attempts with block heater all night and fully charged battery etc. Glow plugs checked out before I did this. Easy fix, try it.
Ted

One possible explanation for your success here: you dislodged algae from the screen filter at the tank.

Funola: Can you provide the "normal factory procedure" you refer to here on this thread so I can examine it and provide feedback.

Dionysius, see post #65, procedure was from Brian. Not sure if it is the official factory procedure or not.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I think the procedure is given in the owner's manual. And I don't recall anything about unscrewing things and hooking up compressed air, or the like in the owner's operating manual. If there is something missing from the instructions MB gives to the person who pays for the car in order for them to make best use of the car MB is really off base. Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

I have looked at post #65 and I find it inadequate. I see no point in disconnecting the 4-Way Banjo (Note: It is not just 3-Way anymore) and could risk introducing air.

Because I have become so frustrated with reams of parallel information I decided to produce a procedure and I want all of you to challenge it and peer review the hell out of it. Here is my effort which I placed in another thread following Leathemang's advice but I am getting very few hits over there.

Please tell me if this is or is not a foolproof and exhaustive procedure. I plan on hanging this on my Garage Wall for reference.

_______________________________________________________________
HELP: Bleeding the Diesel Fuel System on MB 61x Engines - Tech Service Procedure by Dionysius
--------------------------------------------------------------------------

To everybody: Please challenge peer review reword edit this to achieve a debugged procedure to start a diesel on those nasty winter mornings when it cranks continuously but just will not start......
I will focus here only on the fuel bleeding and fuel delivery part. The other checks such as Glow Plugs; Compression; Air Delivery etc. will be added later if people show interest and interact in debugging process.


Low Pressure Fuel Supply Bleeding Procedure

1. Acquire a jar and place circa one inch of diesel fuel into it.

2. Disconnect the cigar hose from the fuel return line to the tank and seal with finger to prevent air ingress

3. Submerge the hose end into the fuel in the jar and release finger

4. Using hand primer and/or cranking continue until bubble-free flow is established

5. Reconnect the cigar hose to the return line keeping it finger sealed as before

Notes:

a. The Injector Pump (IP) fuel supply line circuit should now be air free.

b. Confirm this by pumping the Primer Pump and listening for the characteristic check valve chatter chirp sound. A vibration at the check valve can also be felt when this sound occurs. If this checks OK then proceed. If not troubleshoot the cause.



High Pressure Fuel Supply Bleeding Procedure

1. Crack the nuts at the injectors by loosening a couple of turns

2. Crank the engine whilst observing

3. Witness a small pulsing air free flow of fuel being emitted from each hard line

4. Tighten the nuts as this consistent air free flow is in progress

5. Engine will now start if other critical subsystems are operational

Note :
The other critical subsystems refererred to in step 5 are:
Glow Plug subsystem
Injectors
Clean pre-chamber
Copious supply of clean air
Compression greater than 221 psi on all cylinders
Less than 42 psi difference between cylinders
Operation block heater system if ambient temp is below 10 deg F

I did look for the procedure in the OM but did not find it. It is possible I did not look thoroughly. Can you give me a page number? Thx

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

[QUOTE=Dionysius;1811534]I have looked at post #65 and I find it inadequate. I see no point in disconnecting the 4-Way Banjo (Note: It is not just 3-Way anymore) and could risk introducing air.

The procedure I was referring to from Brian is copied below, which did not work for me btw.

"the "union screw" at the fuel fliter, which is the horizontal outlet line seen in the photo in post #16, should be cracked and the primer should be operated untl clear fuel emerges from the union screw.

Then, the screw is tightened and the primer pump is then operated until an audible rattling sound is heard at the IP bypass valve."

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I found the purpose of this orifice while browsing the Frybrid forum. Chris Goodwin is a very knowledgeable mechanic who specializes on Mercedes and the owner of Frybrid. Here's the pertinent part copied below. Seems like my guess that it is an air bleed was on the money.

"In a normal Mercedes the fuel filter is under pressure since it is mounted between the lift pump and the IP, Bosch put a tiny hole in the top of the filter housing to allow any air in the fuel to accumulate and be released before the injector pump, Like when you change a filter. Since we have a return line and an injector bypass line and this little air bleed and all of them need to return to the fuel tank, Bosch decided to thread the little bleed hole and make a special hollow bolt to go into it, this polt passes through a banjo shaped fitting with 4 connections on it, the little hole that connects through the hollow center, the return line from the IP, the injector bypass line, and the line running back to the fuel tank (Also called the cigar line because it looks like a cigar and is designed to flex absorbing pulses in the fuel system so the people in tha back seat done have to hear "Hiss, hiss, hiss, hiss")."

If you want to see the entire thread it's here http://www.frybrid.com/forum/showthread.php?t=10015

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked