Hoping some of the experts here can chime in on this one. I have just replaced the fuel return / overflow valve on the side of my injection pump on my '84 190d 2.2. When removing the old bolt for inspection, I found that the bolt was just a hollow screw like the ones used on the primary fuel filter housing. I read read on one of the threads that the car would run with the inter workings of the valve removed, but I had been suffering from a poor warm idle and some low power since I've had the car. After replacing the valve, I could only get the car to run for a minute or so, with the pedal down before it starves for fuel and dies, much like the first couple cranks when bleeding the air out of the system. Upon putting the old hollow screw back in, it fires up and after a short time, runs just like before.

Am I missing something simple here? According to the threads I've read here I have the correct part (6010700146) Any suggestions? I appreciate your help in advance. Thanks!

Not sure what you did after you did the installation.

What I would have done is started pumping on the Hand Primer until I was hearing a squishing sound and then pumped somemore. That gets the Air out of the Fuel Supply System.
At that point there is a very good chance that I could start my Engine and it would continue to run.

If I did not do the above and Cranked my Engine Air would get into the Fuel Injection parr of the System (between the Fuel Injectin Pump and the Injectors) where the Air will compress a lot and move only a little bit.

The solution would be to loosen some of the Fuel Injection Line Nuts at the Injectors and crank the Engine until you see Fuel coming out ot them. Tighten the Nuts and attempt to start.
That bleed the Air out of the Fuel Injection System.

If you 190D has no Hand Primer just follow the suggestion on loosening the Fuel Ingection Line nuts.

If the bolt was on the side away from the engine block, this is logical.
Installed on the wrong line it would totally block the fuel supply.


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This is a W201.122 with the OM601.921 = no mechanical primer pump.

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I really appreciate your timely response. I did install the valve in the correct area. Closest to the engine block, however, after your post, I decided to look at the other side and sure enough....someone along the way switched them! So when I put mine in, I had 2 overflow valves installed. After putting it back the way it should be with the new valve installed, idle and acceleration seem to be smoother and when I turn the A/C on I used to loose a lot of power and have a terrible idle. This is fixed! What simple things I overlook sometimes...

What would you expect from a car that had the overflow valve installed on the injection pump where the fuel comes into it from the filter? ... for years?

Constant fuel starvation of the delivery valves.

The only internal delivery valve lubrication is diesel fuel, so there may be detectable higher internal wear.

It would require an injection pump calibration test stand to verify.

Note: If the bypass valve was defective, the wear factors would be minimal.

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Sounds like its time to rebuild your fuel pump. You can buy the kit for around 50 bones, I did mine.

Or buy a new one if you have more money than time or skill (150)

Biggest symptom I had was when at idle sometimes my RPMS would drop, oh yeah and eventually it stopped pumping fuel and it would not start at all!

Fix it before your stranded

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'84 190D 2.2 OM601.911 144K

WOW! Nice catch whunter. You nailed it. I would have never thought of that. I wonder how many mechanics overlooked that ? Maybe that is why you got it on the cheap MB is good at making simple things cause big problems. I got a 1993 300D for about 250.00 that was awesome and the only problem was the alda was bad. Fixed it with a screwdriver, drove the car for a year and then sold it for 3000.00 Thank you ALDA!

If it is running good now i wouldn't worry about it. Get premium AAA service

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

Theoretically if the relief valve found in the wrong place was functioning properly. The fuel could not have gotten by it. You might have gotten the car even cheaper. If the relief valve you removed is sealing then you might have had a gravity pump feed from the fuel tanks return line. I do not know if this is possible but there could be no other explanation I can think of.
Out of curiosity you could check the now spare relief valve.


The problem was simple. The suspecting where it was in your individual case much harder. If you had not found the misplaced relief valve this could have been a long drawn out situation to solve.

The first indication was that the lift pump could not make enough pressure to open the new relief valve for starters. Without using a pressure gauge probably the lift pump would have landed up being replaced or rebuilt. Who and how this mixup could have been accomplished after the injection pump left the factory kind of leaves me wondering. Hopefully not a pump rebuilding shop. I can think of no reason a person or mechanic would have both those fittings off at the same time quickly to enable mixing them up.

Wow, thats worse than me leaving out the pressure relief valve altogether

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

First of all you are trying to fix something that's not broken! Leave the valve as it was and replace the temperature operated vacuum valve that's on the drivers side of the cylinderhead, Second: no power is something that is original in these engines if 0-60 time is within 25 second you are allright.

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600SEL '91
300E 4Matic '88
240D '83
280SE '77
350SE '73
The most complex systems can fail in the simplest way.
Contra verbosus noli contendere verbis, sermo datur cunctis, animi sapientia paucis.

i don't believe in the lord! He's never bought me a Mercedes Benz.

The issue was resolved.
You are wrong, the valve can NOT remain where it was.

I disagree.
My 5 speed manual 190D "0-70" MPH is under 12 seconds with 413,000 miles on the engine.


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Just think how quick it is going to be after it gets broken in.