Hoping to purchase the spring mod from Greazzer in a few weeks. Meanwhile, I’m planning to stretch my IP delivery valve spring back to 27mm because why not?

Of the 240D owners of you who’ve done this, how did it work out for you?
See any difference? Any issues later?

Just FWIW a delivery valve and fuel pressure regulator (what you mean to say) are two completely different things

I stretched mine to about 50mm...

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1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

I’m referring to the side fitting banjo bolt on the IP -the one facing the engine.
If we’re talking about the same thing, the FSM suggests stretching it to 27mm. 50mm is a lot!

NZScott is right, you're talking about fuel pressure regulator spring. Delivery valves are a whole different doohickey.

I can heartily recommend Greazzer's spring mod.

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

Ah, roger that. I’ve already preordered one, looking forward to installing it.
Have you done the stretch?

You want to make sure that you still have overflow from the relief valve after any modification of the spring. Wise to verify it even before. For example the lift pump might be weaker with age and need refreshing as well. Also filter obstruction can lower base fuel pressure in the injection pump.

For example if the lift pump has weakened in age to the point it is unable to open the current relief valve. Changing the spring will do nothing. Neither will restoring the original to the intended length before sagging.

At the same time I feel that having proper fuel pressure in that supply system is important on the 616 engines especially. Fortunately things that can impact this are easy and cheap to rectify if found lacking.

So for those that restore a sagged spring or replace it. If they feel no difference In the seat of their pants especially. Further investigation is warranted.

A weak fuel pump or lift pump if you wish. Is pretty easy and cheap to rebuild. If in a weak condition the chances of failure on the road increases as well. Now that can be expensive. If for example it tests weak you have to eliminate things like a fairly obstructed tank filter is not the issue.

In other words the relief valve regulates the pressure of the fuel in the injection pump. It cannot regulate really low pressure.

There also is considerable localized heat created by the compression of the fuel in the injection pump elements. The overflow from the relief valve removes some of that heat. Yet another reason to keep the system in good shape.

Proper pressure out of the lift pump means a better and more constant flow out of the relief valve. Removing more heat in the process. Over and over again I read posts of difficulty in starting in cold weather. A good lift pumps check valves if sealing well stop back draining. So when they are tired. You start cranking but fuel is not present in enough quantity from the elements to light off intitially.

It instead gets blamed on many things like the engine is old. Where this is true in a lot of cases. The situation if it exists still makes the situation harder than needed. There is a simple test to check this. Say it is thirty degrees out in the morning. Have someone pump the primer pump before you try to start. If there is a massive improvement in start up time. You have a back draining problem to examine that occurred during the night.

To me it is not a case of the valves in the lift pump have failed. As much as crud over the years has accumulated on the valve seats allowing leakage. The kit is cheap to renew them so it is also not a big issue.

In fact after rebuilding the pump if needed it may be good as a test to check it for back leakage. When off the car. When it is not working both valves in it act like two closed check valves in series. .

Why do you check things out before plunging in? In my case I never usually got enough service records to determine what was repaired before I got the car. Maybe that lift pump was rebuilt or replaced five years before and is still like new. I see some people randomly changing things without thinking about this factor. It instead is better to spend the money where the proven need is.

If you want reliability close to a new car. Or as close as you can get in practical reality with cars this age. Over time there are a lot of things to check. I have two 240ds, a 300d NA and a 300d turbo. These are all very old cars. The best thing of all is the needs are cheap in general to address if and when found. If you do them yourself usually fairly inexpensive compared to paid for service as well.


Many are for your own safety as well. In the 240ds you want all the power that is available out of those engines. It may even save your posterior getting into a traffic stream someday. This means checking valve clearances, Chain stretch and some other things that can kill your engine with time as well if ignored.

I stretched the factory spring back out to the 27mm spec. Next time I opened the overflow valve, the spring was broken.

I put Greazzer's spring in, completely happy since. I don't notice any extra power in normal driving, but after Greazzer's spring I was able to pull hills in 5th gear that I'd previously had to drop to 4th gear for.

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

That wasn’t making a rattling noise by any chance was it?

I had it out at about 60mm but it wouldn't fit. 50 it did, It was actually one of Greazzers too (sorry). Nearly impossible to get it to open when hand priming so not really ideal

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1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

My 240D has good compression, properly adjusted valves, and rebuilt injectors. then a year or two ago mileage dropped to 21 or 22. After reading the fuel pressure threads, I made a gauge and tested the pressure per the FSM. Way low. I was lucky enough to buy the overflow valve and a rebuilt lift pump from Greazzer. The overflow valve put the actual operating fuel pressure well above factory minimums. Mileage moved up to 26 to 28. And much more power. Even at 70mph.

Good post of what is possible. A system that checks out marginally at idle. Will further decline under engine load. Starving the engine for the fuel it could deliver if in decent shape further. Another issue is the 616 lift pump by design has a weaker pressure output regulating spring than the turbo lift pumps.

Not the relief valve spring but the spring in the lift pump. My feeling for what it is worth is that over time a pressure differential increases across the secondary fuel filter. This has an effect of lowering supply pressure further in a system. The weaker the lift pump the worse the possible effect. Also as that differential increases dirt that would be stopped by the filter may get forced through.

Since the 616 lift pumps output pressure is weaker than the turbo engine 300d.It may be prudent to change out the secondary fuel filter from time to time. If you fuel at high volume outlets as much as possible the fuel is pretty clean. Small volume places will give you trouble eventually unless you are very lucky.

I live by a simple rule with cars. With any reasonable preventable road breakdown. It is better found and rectified before it creates one. Always far cheaper and you do not also lose a day or more in the process. There will be those breakdowns that you cannot expect or avoid of course.

This poster purchased hopefully a 0-30 or 0-60 pound liquid dampened pressure gauge and used it. This is the right way to do it but you can still get around using that gauge.

This periodic check incidentally is in the Mercedes engine tune up check list of that period. They want a gauge used. The gauge was about 10.00 at harbor freight but might be a little more now.

I have suspected for years that low fuel pressure may be the cause of a very serious problem with the 616 engine. I am not sure I can prove it as the effect I suspect takes place over a long time period very gradually..

So I just decided instead why risk it? Just keep my 240d engines at or above the minimum acceptable fuel pressure. There are also many other benefits in doing so.

Scott, Mark, Barry, I appreciate the thoughtful advice. Mark we're in roughly the same boat sans severe mileage drop. I have noticed it dip a touch however.

This is the first diesel and the only w123 I've ever driven. Therefore, any improvements I experience are entirely relative. To be honest, I don't actually have any real issues (that I'm aware of). The car starts on the first crank, has a fine idle, mileage is in the 25-26 range. Hills are an issue though. I live on a very steep street and pulling out of my drive way in the morning to climb it is a bit of a joke. I'd estimate 7-8 mph and obviously in first gear the entire way. I also struggle mightily to keep over 50 on a highway grade, say 4%.

More than anything, I find incremental improvements to be very satisfying. I imagine we all do. Because I have no clue what this car was like off the assembly line, the idle can always be a little smoother, engine quieter, and hills more surmountable than they presently are.

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.