When you see no change after the spring change. If there also is no overflow from the relief valve. Or none existing before the spring change even.

It is probable there is not enough fuel pressure being applied to the base of the injection pump to start with. Possibilities are tired lift pump, Dirty tank filter or even the fuel filters up front.

Constant overflow to me is an indication that the pressure regulation change or the original configuration is regulating the pressure. Plus the applied pressure does exceed what is needed for the relief valve to function properly.

If you use a fluid dampened gauge. Put a close off valve in the line to it. Those strong pulses the injection pump elements generate can and probably will destroy any typical gauge. So you want to sample the pressure. Not monitor it over a period of time constantly. The harbor freight 0-60 pound cheap liquid filled gauge is more than adequate. It was around ten dollars for a very long time and may still be in America.

One thing not discussed at all so far is a pressure reading at speed. Under loaded conditions. To me this is also important. So I guess the best ideal is a long hose to get the gauge back into viewing range at speed.

Too many people think they do not have enough boost. Or just do not think it is safe to pass. When the reality is the engine is fuel starved for all practical purposes. Really degrading the potential performance.

My suspicion is when the operational pressure drops too low at speed. The engine is out of good power balance as well. Simply because a decent pressure makes the engine a little quieter at speed. This has been reported far too many times to ignore.

I also feel like a broken record. Until I can or someone else can come up with an alternative reasonable answer. Low fuel supply pressure on the 616 may be the cause of the number one rod bearing failure.

In fact if I did buy another 616 engine and it had very low fuel pressure. The engine is noisy enough to cover a wearing rod bearing. I would plasti gauge that bearing. Easy enough to change bearing shells on the first cylinder rod. Before the crankshaft gets scored up.

I suspected that damage may be created over a very long time of running low fuel pressure. Readers probably are aware that the first rod bearing is usually the one to fail. Especially on the 616 engines. Less so on the 617 engines. Yet still happens more than not. To me it trumps having to change an engine out down the road.

Also the 616 lift pump can be upgraded to a higher output pressure just by changing the lift pumps regulation spring from a 617 turbo engine. Leaving the lift pump as original makes the fuel filters restricting effect greater as it ages. Plus it will help to keep that higher pressure relief valve functioning better.

In manufacturing the 616 engines lift pump. It was designed to have a lower original output pressure. Same as the naturally aspired 5 cylinder I think.

Before I entered the picture it was assumed the first rod bearing failed because it was the last bearing on the crankshaft to see oil pressure.

At the time I was asked why they failed. After a lot of thought. I felt the old answer just did not hold water. Both engines have about the same oil pressure. The number one bearing on the 5 cylinder is even farther away.

Plus the loading of the cylinder is greater on the turbo five cylinders. So technically in my mind it should fail more than the four cylinder 616 engines experience.

Make no misteak though at the same time if a rod bearing fails even on the 617. Chances are very high it will still be the number one or two rod bearing on them.

When most of us acquired these cars they were old already. So I also considered the possibility of sludge build up in the oil passages from the lack of oil changes. Then again if this were the case. The oil has to travel farther to get to the number one rod bearing on the 5 cylinder. Leaving me with the only other difference being there are more power strokes per revolution on the 5 cylinder than the 4 cylinder . At the same time the five cylinder turbo power strokes are much stronger.

To remove sludge an old engine. I thought that a quart of miracle mystery oil in the base. Say every second oil change for awhile. Would slowly reduce it. It seems a bad ideal to get it all loose faster. That can block oil passages you are trying to clean. With resulting destructive results. Although people switching over to synthetic oils have not reported the problem either. It does have a cleaning action as well.

There also where some other considerations. Operational RPMs are higher on the 616 on the highway for example. So my only certain conclusion was it is better to have good operational fuel pressure than not. With one perhaps still remote possibility. That otherwise it might also shorten the engines life substantially by not having it.

I designed a test to perhaps prove the concept. It is an involved test and could cause me pain in also indicating something else to investigate. So I just made sure I had good operational fuel pressure on my cars.

So I leave this post with if a spring is changed and there is no difference. Either you had high operational pressure before. Far more likely though is you have another problem present in the same system as well.

This area in general is about the cheapest area to restore. Yet there has been massive resistance to even checking it out properly. In the majority of cases it is also great preventative maintenance to reduce episodes of quitting on the road.

Things that are becoming sub standard in the fuel supply system generate gradually lower and lower than desired fuel pressure readings first. Usually the fuel supply system just does not suddenly pack it in from being a good normal one on these cars

Plus as a fuel filter builds resistance to flow. The pressure differential across it increases because of the lack of changing it. This could force more dirt through it than intended by the filter designers. I could write a manual perhaps on what preventative maintenance should be done. To stop all too many cases of premature engine failures.

I am very lucky in that all four of my 616 and 617 engines are in very good condition overall. One original engine in a car with a perhaps honest 165 thousand miles and another being a total drop in by a Mercedes dealer not long before I aquired it. Years ago now. Both those cars indicate to me just what they were like when pretty new performance wise.

Last Spring just sold ! All gone. Thanks Everyone !

Please PM me when you have another complete unit to purchase.

__________________
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1998 VW Cabrio
2001 Audi SomeRoad A/T (no air suspension)
2003 Audi DeadRoad M/T (no vroom, for later)
2002 Audi NoRoad A/T (nothing under the hood, being rebuilt)

Shouldn't be too long a wait .

Remember : you have to send your old one back ! .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Will have five (5) units for sale, that's a cleaned OFV with the mod'd spring installed, ready for install. The Buyer will have to either re-use their aluminum sealing washers or get new copper ones. The original aluminum sealing washers should work just fine unless they have been really distorted (which means someone in the past has tinkered with the OFV).

$40.00 shipped CONUS. I have given up on folks returning their OFVs for the $5.00 refund so no need to send anything back / no core deposit / no core deposit being provided.

Taking orders now (paid) HOWEVER -- these will not be shipped for approximately two (2) weeks. First pay, first get. I do not "reserve" or hold nozzles, OFVs, or other parts any longer.

Apparently, two (2) are spoken for.

Down to three (3).

As noted above, there will be a delay in shipping these. If you pay now, you are guaranteed one.

Thanks again !

Thanks Again .... all spoken for !

I'm not very damn happy with this forum right now; didn't ever get notification of any other post in this thread, until today!

If you build more, could you PLEASE PM me as I asked? Thanks.

__________________
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1998 VW Cabrio
2001 Audi SomeRoad A/T (no air suspension)
2003 Audi DeadRoad M/T (no vroom, for later)
2002 Audi NoRoad A/T (nothing under the hood, being rebuilt)

I will try to remember ... not intentional ...

Pardon me for asking, but why would one want to increase the pressure when Mercedes gives a specific value range of pressures that the pump should see? It would seem that the risk of damage to the fuel system would be very real if you increased pressures beyond the factory specified 1.0-1.3 bar.

The manual says that if the pressure drops below 0.8 bar to simply remove the spring, stretch it to 27mm and then check the pressure. If it's not within the specified range the hollow bolt assembly should be replaced with a new one and/or the lift pump should be replaced or rebuilt.

After all, the new part from Mercedes (000 074 72 84) is only $27.00 list from any dealer, probably less from some.

Just wondering....seems like a rather dangerous thing to be doing, not to mention a possible waste of money...

Mercedes did not design the fuel system. Nor did they produce it to the best of my knowledge. The designers of the system had concerns that perhaps have not proved to be justified. The minumin operational pressure has validity.


They did expect certain levels of maintenance that in general was never performed often if at all. They perhaps where also the first to produce a diesel fuel system with no water and sediment trap. At a time when this was far more important.


Increasing the base fuel pressure does result in better filling of the injection pumps elements. Producing more power if the rest of the fuel system is in good condition.


Mercedes does recommend periodically checking it with a gauge but again is seldom done. This very old fuel design system is both really durable and reliable if a general maintenance check is done every few years. Otherwise the chances of being stranded along the road somewhere are increased. Most maintance is also cheap to do.

In addition to the other replies ;

Because I personally have opened quite a few of these and _every_single_one_ has had a worn out spring ~ not only do coil springs have a finite life span but the check ball sits directly in the end of the spring and moves constantly, this wears the open end of the spring until it fails ~ many I have seen were paper thin and crumbled when I touched them .

As mentioned, older German cars/mechanics/engineers all assumed you'd be endlessly under the hood cleaning, adjusting and testing things .

A Mechanic I know was trained in Germany, by Mercedes but thinks they're '****' because of this aspect ~ he drives a Lexus and will trade it in long before it reaches 80,000 miles so he sees no point in doing the things we Diesel Heads consider normal .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

People run 45 psi (3 bar) no problems. I stretched the spring so tight the return line has only the injector return fuel going through it. And that's after I "de-stretched" it Sorry to Greazzer for going beyond his springs intentions

__________________
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

In addition to the "performance" aspect, there's also a service/functional aspect to using one of Greazzer's overflow valves. On the later vehicles (60x engines) the overflow valve has a fairly weak spring and a plastic element inside of it. When (not if) the plastic element warps or breaks, the fuel pressure in the fuel rack drops at low RPMs and the "check valve" function of the overflow valve is lost. The result is (or can be) rough idle, poor low-RPM power, or rough starts from cold when sat.

I had the latter issue with my SDL. A new overflow valve from the dealer with tax (or ordered online with postage) is roughly what Greazzer is charging for the older style valve that gives a positive seal and can be serviced in the future when it gums up or gets spring fatigue. Since I can't seem to find one of the valves to save my life, the choice to pay the dealer or Greazzer was a no-brainer. My car is much happier in the mornings, no more craptastic cold starts.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

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

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

As an update: I am currently all sold out and none have been ordered. To the various folks who have PM'd me or emailed me, I will post here when I get some. Generally, I do not reserve parts, nozzles, et cet., and that would include OFV springs. Unfortunately I take this stance because too many forum members have screwed me around in the past by emailing me or PM-ing with this or that request for nozzles, parts, et cet. I would go get nozzles, parts, et cet., and then I would never ever hear back from the forum member, not even "I sold that car" ... "that car got in a wreck" ... so I got stuck holding stock until I could sell it.

I am anticipating getting maybe an order of around 50 so that would be plenty for folks who want one.

Thanks in advance.