I have a junk 300d that I pulled the spring out of. Check peach parts to see if they have it, or MB

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1977 240D turbo

FWIW, it may not be that big a problem today, but sometimes tires from different manufacturers won't be exactly the same size, even if they're marked the same.
My latest 240D came with a set of 8-year-old, dry-rotted 205/70R14 Firestones mounted on Buntd-rims. They rode well, but looked huge on the car and more suitable for off-roading. And they cornered like marshmallows!
I had a spare set of Buntd-rims with old 205/70R14 Michelin-Xs. The Michelins were nearly 1.5 inches smaller OD than the Firestones.
The new 195/70R14 Michelin-Xs I put on the car were very close in OD to those old 205/70R14 Michelins and my odometer accuracy appears nearly dead-on. Plus steering response is much better now.

Happy Motoring, Mark

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DrDKW

Well, after another couple hundred miles I'm still happy with the change. I've tried holding it in 3rd til 60 mph and it makes a difference but it really sounds wound tight at that speed. 50-55 sounds less tortured and works out ok for acceleration purposes. I did a 0-60 time and it has dropped from 28 sec to about 24. That's leaving it in 3rd til 60 which seems to result in better acceleration.
To any of you who are thinking about making a final drive ratio change on one of these, I say do it. If you have a lot of highway driving with low to moderate hills you won't be disappointed and if you have a lot of in-town driving the first 3 gears are more useful also. The cabin noise level is soooo much better and the driveability (except for uphill between 50 and 60) is greatly improved. I still need to make the best of the state-of-tune of the engine but even without a fresh valve adjust and timing check the overall effect is positive.

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1983 M-B 240D-Gone too.
1976 M-B 300D-Departed.

"Good" is the worst enemy of "Great".

I have slowly come to the additional conclusion that all lift pump pressure determing springs should be changed out on the 616 engines.The 617 lift pump springs are easily obtained used.

The availability of higher lift pump pressure somewhat minimizes the effect of poor flowing fuel filters as the accumulate junk from the fuel slowly restricts them. First thing to occur is the relief valve no longer is remaining open as you are then below the threshold point.

This alone changes the injection pumps ability to function correctly to some degree. So without a pressure gauge installed the higher available pressure from the 617 spring is going to protect that number one rod bearing somewhat better than the 616 spring just in itself.

Those pressure spikes do not see either the return line or cigar hose when the relief valve is closed. As operational pressure declines the elements for some reason indicate they no longer load equally.

I really believe that is why the number one rod and cylinder wear excessivly on the 616 compared to the other cylinders. There is really no way to verify this thought other than setting up and doing certain tests that I really do not have time to do.

Just on the chance I am right about this it is really wrong to ignore the possibility. Nothing has occured to make me change my mind since I first considered it the probable cause.At least of of the number one rod bearing failures.

There is a much lesser effect on the 617 but the same theory applies. It is not only attributable to fuel pressure. Possibly the use of higher lift pump pressure to service the system on the 617 may account for a good portion of the difference as well.

I am still waiting to see a lot of initial pressure reports from people using pressure gauges to get some sort of handle on how widspread low pressure at operational speeds and others is present. I believe the 616 engine may even be a little less noisy at speed with good operational fuel pressure versus lower. I still also feel the installation of a gauge is a good ideal.

Does the 617.912 use a different spring than the 617.952? If so I think I'd be up for the change. Also been thinking about an aux electric fuel pump.

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1981 300TD 4 speed manual
Euro bumpers, zender valance and skirts, H&R springs, billy HD's, leveled sls, real AMG Pentas 16x8 et11, vdo boost/egt gauges intergrated into ash tray, eurolights, led 3rd brake light

I just looked up the price for a lift pump on A.P.E. 300D $182.79. 240D $204.05. looks like the only difference is maybe the lift pump spring.

I have an extra pump, maybe I`ll swap the spring into the 240. then hang on .

some where I need to source a fuel pressure gauge. then grab a fuel line from PNP to cut and splice in the gauge.

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Sounds interesting. I'm working on an auxiliary electric fuel pump also. I wonder if the combination of positive feed to the lift pump and a 617 spring would make a difference.

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1983 M-B 240D-Gone too.
1976 M-B 300D-Departed.

"Good" is the worst enemy of "Great".

Unless on vegatable oil I see no benifit or need for an electric booster pump. The original pump is very durable and has good function. The only thing is perhaps at higher milage the valves in it should be addressed.

It is only a 10.00 kit from the site sponsor and should be manageable by everyone on site. The need to address this still depends on a pressure gauge.

Shutting the return line on the injection pump off will indicate the maximum output pressure the lift pump can produce. Generally thirty pounds or more the valves are probably still fine. This is the 617 lift pump or the 616 lift pump with the 617 spring in it of course.

For a multitude of reasons I am not happy with just stretching the relief valve spring to increase pressure.Without a gauge you may never know where you are. In many cases there will not even be any improvement as the whole system is substandard with aging, fuel flow restrictions etc.

I do not have the figure for the 616 pump with the original pressure spring. Other than it is lower.

The chinese 0-30 pound gauge that is liquid dampened is available in places like harbour freight. About ten dollars. Others may chime in as to where they got theirs. Or have seen them. Overall for the money that is not a bad gauge.

I think that's a bad idea. There are very few elec pumps that will not starve the stock lift pump of fuel at high rpm.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

There is some truth to this in my experience. A 240d owner phoned me and complained of having a top end of fifty miles an hour. When I eventually saw the car it had an electric fuel pump that was probably the issue. The lift pump was bad and they had substituted the electric pump. I suggested he repair the lift pump before doing much else.

Never knew what he did. Probably thought the old guy was crazy.

The only way I'd consider an electric pump is to eliminate the mechanical one entirely.

That said, the pump used for the 7.3L Powerjoke is about perfect for our needs. High flow, moderate pressure, simple hose barb inlet/outlet and can be found for around $100.
Wiring is dead easy. An oil pressure switch keeps it on and the glowplug relay bypasses the oil pressure switch to turn it on when the engine is not started yet. Added benefit; loss of oil pressure will cut the fuel supply and stop the engine automatically.

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And it's got fancy naugahyde upholstry too

I checked the fuel pressure on my 240 before changing the pump spring, and it was about 10 psi. After changing the pump spring I did stretch the relief spring checking it with a gauge to see what I was doing. 21 psi under load now. I do not see a need for an electric pump in addition to the lift pump. The lift pump seems to hold pressure just fine. As Forced has said one or the other.

For the gauge I drilled and tapped the banjo bolt that the fuel enters the IP. 1/8 pipe thread is the size I used. Make real sure no filling/chips etc are left in it. Of course do this off the car. I really would not do anything without starting with a gauge.

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1977 240D turbo

If you could mention any observabe changes at the higher pressure over the old pressure. It would be helpful to others. Especially since yours is the 616 or four cylinder engine. I know for sure myself and a few others are always interested in what transpired.

If you are on vegatable oil of course any sensations of changes are reduced. Funola made me suspect that much higher pressure increased his milage substantially on wvo to diesel fuel levels.

Before that we always thought it was just a fact that wvo burners got less mpg but since the fuel was cheap it really was not too important. If it actually contributed to increased mpg my further suspicion is it made a better cleaner burn. That of course is going to make burning wvo less damaging to the engine as well.

Funola was operating at about thirty pounds pressure in the injection pump base to enable this. Because the wvo has far more viscosity than diesel fuel. At that elevated pressure I fell it does not get the injection pump profile or calibration into a new area.

. On thinner diesel too much pressure can in my opinion change the injection pumps running calibration. Nineteen to twenty pounds should be fine for diesel.