what did you use for shims?

.

I have cut the piece of the proper sized nail and sand the edges a bit,...easy

edit: if I remember properly you can't go over 3mm shim as you would lose holding ground fot the spring...

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w126 500SEC gen II euro, powered by OM617 turbo stolen from 84 300SD 2.88 diff,EGR blinded
next wish/project: w114 coupe OM603 powered

Interesting... thanks = )

If your spring was really weak in the relief valve. You should notice at least some improvement in the idle sound. It is very hard to prove various suspicions. Poor substandard fuel pressure. Seems to impact the power balance of the engine to some extent.

This I imagine I could prove by working up a test car. One test usually reserved for trouble shooting. Is to close off the relief valve output. If there is a positive change it indicates at least the lift pump has a reserve pressure capacity.

There is no problem doing this. As you are partially deadheading the lift pump. It just settles down at whatever pressure it is capable of producing for the test. Nothing gets damaged.

Now for what changes with elevated fuel pressure in the base of the injection pump. In effect I believe you are turbo charging the loading of the elements in comparison to lower pressures. By putting the spring from a turbo lift pump in the 240d lift pump. You may get overflow even at thirty pounds base pressure. The elevated pressure works to defeat the very strong pulses that occur in a running injection pump.

Actually they cannot be defeated but only their negative effect reduced. You still want constant overflow out the relief valve as the cigar hose does work to reduce or moderate them as well to some extent. But only when the relief valve is open. In design it was meant to always be open when the engine was running. To allow the pulse moderation with the cigar hose.

For those cases running with no overflow it may be best to consider moving the cigar hose to the input of the injection pump. Or installing another equivelant there. I considered this a long time ago but did not post the thought as I was reluctant to recommend any pressure above 19 pounds.

Over time I have wondered if I was too cautious. I also believe at high pressure the effective dynamic timing is increased a little. Again something that is hard to prove.

I wish someone would install a cigar hose or the equivelant of one in the input circuit to the injection pump and see if there is a noticeable difference.

I think there may be some on those cars that cannot reach the high regulated overflow pressure. Perhaps even on those that can. Some inline pumps had to install steel barriers to prevent damage to the casing from those vicious internal pulses generated by the elements over time.

I have to also include a caution. There is no proof one way or the other if high base fuel pressure is detrimental. This system was designed with reliability in mind so the operating fuel pressure could be created in a durable fashion. When you raise the pressure above the recommended amount. The lift pump is working harder. At the same time it is a robust design.

So much time has passed. Perhaps I can suggest another of my unmentioned ideals. At least a few members have a good ideal of what is going on now.

That is to feed the injection pump with a fifty pound very common car electric fuel pump. Based on there seems to be ever better performance as the pressure is elevated more. When you start these kinds of experiments. You must use a pressure gauge. Plus stay objective.

Another effect of running sub standard fuel pressure is a noisier engine at speed by the way. This to me relates to the lift pump only recharging once with every rotation of the injection pump. Start the element loading with low pressure. It declines further all the way down the sequential line. Impacting the power balance. Again something not proven but highly suspect.

There was one member running a proven solid thirty pound pressure on a 240d. What he reported was quite impressive. I do not think the stock lift pump on a 240d can generate this pressure in the base of the injection pump without the turbo spring installed in it. Actually a simple modification.

These springs show no issues of signifigantly weakening with time so far. So a lift pump spring from any old turbo pump is probably still good to use. Just installing a stronger spring in the relief valve may not be the end of the rainbow.

I really thought others would put it all together over time. At my age you never know how long you are going to be around. So I thought it was time to post some of my earlier unmentioned thoughts. Food for thought and still room left for experimentation and development perhaps.

Barry -these pulsations you describe, are they physical, or aural? Engine shake, engine noise? How do they manifest and when might I notice one?

I removed my cigar hose about a year ago as it was leaking. I had plenty of 5/16th hose lying about so used that instead. I remember asking the forum about the function but never received a clear answer about these "pulses."

The cigar hoses are an odd component. Sometimes they make a difference in some way and other times not. Most euro version cars with a different series of injection pumps did not use them.


The common belief was they also suppress noise in north America. The pulsations are both. Of course you can hear them on some north American cars with the cigar hose removed it is claimed. Reputed to be a buzzing type of sound.


I really believe they were meant to suppress the pulsations to some extent as well.


Another factor is in the south being made of rubber they probably harden with age and time. Or at least more so than in the north.


Personally If the car had one I would replace it. I was only involved with one strange case. Where the poster had a strange effect depending on his fuel level in the tank.


I suggested he replace the missing cigar hose. There were many that thought with good reason It would make no difference. The reality was it eliminated his problem.


I have no ideal if this was perhaps a strange reaction involving more than just the cigar hose or not. What it proved to me though was it can make a differance in certain situations. Or in many cases you may not see one.


These pulses that are generated in the injection pump are very strong. They will make a pressure gauge that is not internally fluid dampened slam from one end of the gauge to the other. Even with a dampened gauge you will average the vibrations for a reading. We are also talking a hydraulic form of action with the fuel. It will telegraph these pressure spikes as the fuel will not compress. It is very hard to get a picture sometimes that has enough clarity.


If I remember accurately his car would only run well below or above a certain fuel level. It really acted up if the tank was in the troublesome area. All I was sure of is the lack of the cigar hose was creating some issue . Perhaps the strength of the combined pulse being trapped more above a certain fuel level in his tank where reducing the flow of fuel into the base of his injection pump. His problem was pretty pronounced.


Fortunately for him he mentioned in his post that the cigar hose was not present. Or this problem might have been really difficult to get to the bottom of.


Remember that long ago when he had the issue. The general belief at best was it reduces spike noise. Kind of a muffler I suppose. Even long ago I thought it moderated the overall pulsing effect at least a little. acting as kind of a pulse accumulator. In the process knocking the severe peaks down.

That makes a bit more sense, thank you kindly for the reply.
The next time I make a harbor freight run I’ll pick up a gauge and gather some numbers. I have no reason to suspect anything is off, but again, my experience is n1.

I often do not subscribe to the mechanical visualizations which Barry presents.. but that post about the Cigar Hose was right on the money...
Are they available new still ?

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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

I found a few on eBay... around $17. Boy, this is really death by 1000 cuts =)

Cigar hose (MB 008-997-64-82), genuine new Mercedes Benz part available for $15.50 from the forum sponsor, (plus two other choices for less).

The searchable online parts catalog of the forum sponsor is at the top of this page.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

I appreciate Barry12345's thoughtful, detailed posts. A boon to us shade tree mechanics. I think it is important to understand a system and not stab at possible fixes. I put a liquid filled 0-30psi gauge in the banjo bolt on the fuel filter that feeds to the injection pump. In a spare banjo bolt from pick-n-pull I drilled and tapped an 1/8"NPT thread. Use an 1/8" galvanized nipple just long enough to place the gauge between the oil dipstick and the cylinder head cover. Take out the banjo bolt and put in the gauge assembly. Start the car. The gauge should read 9 to 12psi. Run the engine up to 3000rpm. The gauge should read minimum 12psi. This is the pressure allowed by the overflow valve spring tension. The spring gets stretched to increase the tension and thus the pressure. Now do the same test with the return [cigar] hose pinched off. The readings should be minimum 16.5psi at idle and minimum 19.5psi at 3000rpm. this is the actual pressure the lift pump is able to create. Now one knows where to start with repairs.

I've been running my swap for nearly 40k miles without a cigar hose. No issues that I can attribute to it, and I don't plan on installing one.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

Alec - found the hose on pelican right after I checked eBay. eBay is generally my first port of call to establish part numbers, due to their intuitive search engine which in turn makes searching pelican much easier.

Mark- Appreciate the instructions! Been looking for those specifics.

Stretched the overflow valve spring a couple weeks ago and I've since noticed my engine running slightly cooler. It's hovering a hair above 80, whereas previously it sat around 85. Unless I'm getting some new combustion efficiency and stepping on less pedal, I can't figure out a correlation.

Likely a total fluke, but anyone else experience this?

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1981 240D 4sp manual. Ivory White.

For those not having a cigar hose and not wanting to spend the money. Even a used one from a pick and pull. If still pliable is probably better than none. It certainly hurts nothing to have it.


This 616 engine was discontinued by the manufacturer in Europe. Then manufactured later and sold in India I think. I often wondered if any type of updating it was employed there?


How many years later it remained in production there is also unknown to me. To the best of my limited knowledge I have never seen a poster on our site that owned one of these. Indian built engines.