I might have guessed!

However, I'm not alone in this;

see

What does the cigar hose do....

and a few posts either side where whunter also pulled some pumps off the shelf, tested them, and found the same.

I think these posts were made during the time when you weren't actively posting.

While there are some double acting lift pumps - Bosch did make them - most actually pump in the way I've described.

It's possible that the pump you looked at is one of the double acting types.

The pumps on some of the 14.62 litre MB V8s fitted in trucks used to have these double acting lift pumps fitted, and they are the only place I've seen them used, but, it's possible (but odd) that they're fitted on smaller engines.

So, only one lift pump pressure pulse for each 4 (or 5) injection pulses. I guess that it must fill quickly between two injection pulses and spring return during the entire time of the next 4 (or 5) injections. So the cam lobe for fill must be some what less than 90 degrees of rotation

__________________
Ron Schroeder
'85 300 Turbo Diesel 2 tank WVO
'83 300 Turbo Diesel 2 tank WVO
Some former WVO vehicles since ~1980:
'83 Mercedes 240D
'80 Audi 4000D
'83 ISUZU Pup
'70 SAAB 99 with Kubota diesel
'76 Honda Civic with Kubota diesel
'86 Golf
Several diesel generators
All with 2 tank WVO conversion
LI NY

>>I guess that it must fill quickly

Yes. However, the full stroke of the cam isn't normally used.

As the fuel is delivered by the spring, the piston only moves along the bore of the pump corresponding to the amount of fuel delivered. As the piston progresses, the spring force pushing it drops as the spring extends. This means that the over-pressure that the pump produces compared with the relief valve opening pressure drops, and the fuel flow rate slows. If the cycle happened slowly enough, the piston would stop as the relief valve shuts, trapping fuel at pressure in the system.

The worst case of pressure fluctuation happens at low engine speeds, when the piston has the longest time to deliver fuel - at higher engine speeds, the fuel pump's piston will barely move, and the pushrod will only touch the IP cam for a very small angle of IP rotation.

The full stroke of the cam is only used when there is no resistance to pump against - say if there's a lot of air in the system, or if the relief valve has failed in the open position. The large spurts of fuel one sees when cranking the engine with a pipe off are much larger volumes of fuel than the lift pump normally delivers each cycle.

Is there one of these on the M603? My 87300TDT will sometimes start right up and then stall and it is very hard to restart. Almost like it is starving for fuel and lost it's prime. Any of you guru's know if there is a check valve or a lift pump that could cause this?

Pulled my spring out and measured- 20mm- not bad I thought considering the mileage (219K). My engine has the shakes about 50% of the time when I come to a stop and leave it in D, put it in N and things smooth out. So I stretched the spring out to 24mm and no noticeable difference, but hopefully the IP is retaining a little more juice now. I still want to rebuild the lift pump and replace the plunger with the new style primer for peace of mind. I would also like to measure the fuel pressure before and after rebuilding of lift pump springs. Anyone try rigging up a gauge with a sending unit between the secondary filter and IP?

__________________
83 300TD 219K HOMER

Your idle shake could be a bad rack damper pin.

Item Number: 0000742674
Main Category: MERCEDES BENZ
Sub Category:
Description: diesel injection pump "Rack Damper" adjustment bolt...Rear of Injection Pump
Weight: 1.000


so, what does that rack damper bolt (617) actually do?
http://www.peachparts.com/shopforum/diesel-discussion/183139-so-what-does-rack-damper-bolt-617-actually-do.html#post1458468

Part# rack dampener pin for 1985 300SD
http://www.peachparts.com/shopforum/diesel-discussion/120005-part-rack-damper-pin-1985-300sd.html#post858324

Replacing Rack dampener pin
http://www.peachparts.com/shopforum/diesel-discussion/176580-replacing-rack-dampener-pin.html#post1391845





Have a great day

__________________
ASE Master Mechanic
https://whunter.carrd.co/

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

Please read the following thread.

Fuel injection pump starvation with good a good lift pump
http://www.peachparts.com/shopforum/diesel-discussion/247039-fuel-injection-pump-starvation-good-lift-pump.html#post2133911

Your bypass valve is a sealed unit..

The more likely issue will be one of these:

* OM603.960 and .961 Plastic fuel lines, injection pump

* OM601, 602, 603 Lift pump Repair kit

* OM603.970 Injection pump output Re-seal

* 6010700282 Fuel Thermostat

* Diesel fuel thermostat repair kit, huge application list

Great information in this thread!!!!!

Several people have with interesting results. They used a tee arangement with a dampened 0-30 pound mechanical glycerin filled gauge. No one has tried an electrical gauge with a sender yet that I am aware of. It has reciently been discussed though.

There is a more than fifty fifty chance your system is quite low in injection base pressure. This is based on no change at all after your relief spring stretch. If the internal base pressure in your injection pump cannot even reach a pressure that opened the relief valve under the pre spring stretch senario.

Certainly by changing the spring length nothing is changed. No or very little pressure has been proven to affect idle to some extent. Most spring stretchers almost always reported an improvement in idle. The ones that reported no change in any dynamic I felt probably had a very sub standard condition initially and still had it.

Anyways you seem to have trouble by what I can accertain from your post in your fuel supply. You really should get a gauge reading and procceed from there. You have everything to gain and nothing to lose in my opinion.

Let us know if you go this route and how things work out. We still need good examples posted for general information.

Forced Induction,

IIRC, you posted a page from the FSM about this spring needing to be 27.0mm OAL. Out of curiosity this morning, Dad pulled the IP releif out of his 617.952 IP and found the relief spring to measure 20.0mm OAl. Since my car is currently in his shop, he pulled the IP relief valve from my 617.950 IP and found the relief spring to be 21.0mm OAL.

Now, in my most humble opinion, stretching or even shimming that spring to the 27.0mm you mentioned in your post seems extreme. What is your opinion on this???

__________________
Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

It would have been nice for this post to be attached to that thread so it would be easy to reference that page he posted...
Perhaps specs changed over time...and stouter wire was used.... which would change the uncompressed OAL.....

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

That's what we think since 7.0mm is a considerable amount. However, Forced Induction's post stated (to some effect) that the IP relief valves are all the same, IIRC. The reaon I posted this separately, was not to confuse this with any of the data from the previous postings...Robert

__________________
Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

My opinion is there is already a thread on this exact topic still on the first page of the forum.

Yes,

And even you questioned the vaildity of the 26.0/27.0mm suggestion from the FSM, so I thought some calrification would be in order...Robert

__________________
Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

Dr. Bert. You can imagine my concern when some individuals where stretching their springs to 26-27 mm.

Some of those relief valve springs were only meant to be at about 21.5 mm originally. I could not even estimate the base pressure they were running if their lift pumps were really still good.

Needless to say these individuals decided not to use gauges. I had no desire to see possible damages occur. Especially with so many unknowns. Yet where some of them landed up was quite interesting. It did open a possible future window at some point yet to come.

Of course it was not from a known pounds per sqare inch perspective. Some might have been above twenty five pounds in my opinion.