I found this last evening while searching for information about delivery valves.


Bosch Injection Pump Delivery Valves | Diesel Engine Troubleshooting

Bosch Relief Valve and Pump Pressure Test Diagram | Diesel Engine Troubleshooting

Both of these gave info that I hadn't seen before. I haven't read all of the related posts. I'll heed the 2nd one & test or change my pumps return valve soon.

To me, the two posts wording also reinforces the importance of lubricity, even for the pumps that have engine oil as the primary lubricant ( the delivery valves have moving parts that can wear with decreased lubricity due to heated fuel ). That's the reason I always try to add some lubricity via an additive to each fill-up. To me, the added lubricity might keep the delivery valve itself functioning properly longer. It has to seal tightly or there can be injection fuel dribble and secondary injection. It seems that the injector moving parts would also benefit from a little added lubricity.

There are quite a few other Bosch topics covered. If you click on the "Bosch Fuel Systems" category on the right side. The list covers quite a few posts that have been previously entered. It appears some/most posts are missing diagrams ( don't know why ).

The OM60x series engines don't use a pressure-regulated relief valve. It is a drilled orifice. They never wear out to where they fail to regulate pressure. They have a plastic check valve in them to help maintain priming, but nothing to regulate pressure. If you aren't getting an aired up fuel system, don't waste your time changing it, you'll gain nothing.

The Bosch P pump referenced in the article is similar to the MW pump used on the earlier engines and DOES use a spring/ball for the pressure setting. Your car does not.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

this is why there is a large amount of fuel flowing through the Fuel In Jection Pump and back to the Fuel Tank where it can cool off.

I don't know if these sites are any good any more but if so you can see lubricity rated.
Spicer Fuel Additive test results
http://www.dieselplace.com/forum/76-gm-trucks/64-maintenance-fluids/177728-lubricity-additive-study-results.html#post1963830
Pdf http://www.eng.wayne.edu/user_files/414/file/Quick_Upload/Lubricity_%20Kapila%281%29.pdf

Also in 18 years as a Diesel Mechanic I have never scene any sort of Diesel Fuel Cooler and in the past Cummins and Detrioit Diesels used to run their fuel through passages in the Cylinder Heads. (Except for the really old Cummins which had external lines.) Which of course warms up the Fuel some before it gets to the Injectors.
On those they also have a large fuel flow back to the tank compared to the amount that gets injected.

__________________
84 300D, 82 Volvo 244Gl Diesel

This diesel technical info is pretty much all new to me. Not enough time in years left to have a good understanding of details.

I found a few more sites that give some good information:

http://www.w124performance.com/docs/Bosch/http://www.w124performance.com/docs/Bosch/

Hard to fathom how much time was required to build a website like W124 Performance. Hope it stays up for several years.

I was able to download a long pdf on my Note 4 Samsung. For some reason the document won't load on my computer. Probably just as well, might be loaded with viruses.

PDF is a Bosch document about 150 pages long that covers Diesel fuel injection pumps. It used to be available for sale on Amazon and several other sites.

Name of document is: "Diesel In-Line Fuel-Injection Pumps" printed by Bosch 2003

" D 300 ", I haven't pulled the pressure relief valve behind my OM606 banjo bolt, but I've found a few pictures of what the innards might look like.

I guess the ball & spring is to stop back flow when the engine is shut off???

Supposedly for OM606:
OM606: Fixing the overflow return valve design

http://www.peachparts.com/shopforum/diesel-discussion/341977-who-really-knows-606-injection-pump.html post # 9 shows picture

A few other engines: ( something so simple can cause poor performance )

http://www.peachparts.com/shopforum/diesel-discussion/247039-fuel-injection-pump-starvation-good-lift-pump.html

It's sure easy to overthink something when you think you understand it but really don't. The OM60x relief valve regulates pressure by restriction, not by spring pressure. The pressure in the fuel rack is set by resisting flow through a sized orifice. The plastic "flap" is in there to serve ONLY as a check valve. If it falls apart, yes it'll cause problems. If your fuel system isn't airing up overnight, it isn't your problem - look elsewhere.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Texas, you have to think a little bit out of the box or perhaps from the designers point of view, what were they trying to achieve.

The overriding feature of this design is....

..fuel pump, it needs a running engine to function so all fuel must be up front and in place without anything happening electrically.

When viewed from this standpoint (no leccy pump) it's easy to see why the components are arranged as they are, the lock between DV and injector give instant fuel within a small revolution, backing this up is the gallery immersed in fuel, this in turn is supported by the SOV which closes the circuit (twice, two valves).

Follow this back and it starts to become logical ..

__________________
David


1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)