Sounds like something to do with your fuel filter instal . Your talking about the filter at your fuel pump correct ? rear of car .
is possible some debris / dirt got into the system or that perhaps you crimped a line causing low fuel pressure .
Lots of things happen when cars sit .
You need about 28 Lbs at your fuel rail ( checked at your cold start valve ) Also Possible could be a fuel Regulator could have gone bad this can all be checked with a fuel pressure test . just undo your fuel line at the cold start valve and hook up a fuel pressure test gauge to test your fuel pressure.
Another thing I see happen often when these cars sit is The AAV Valve stick
( auxiliary air valve ) This Valve can be cleaned . the plunger at the bottom of the Valve gets gummed up and stuck causing the additional air to keep running in to the motor after it has warmed up rather then shutting off the air flow . this will make the car stall when warmed up. To check this Valve you can simply remove the air cleaner leaving the wire attached to the small valve on the air cleaner ( just twist the air cleaner to the side with wire still attached ) and you well see where the AAV Valve air enters the intake at a hole about 1 inch . start the car and you well feel air coming into this hole to enter the Engine . when the Motor reaches operating Temp the air should be almost shut off coming from this AAV Valve . if not then Valve is stuck wide open and Air just keeps rushing in and the car well stall most likely or run very poorly .
Cleaning this Valve :
Tricky , remove the Valve and heat the lower part of the Valve in hot water ( Boiling water ) then ( after marking just how the Valve is lined up ) you can twist the top of the Valve up and off with some large Channel lock pliers . It well be on hard and require some hard twisting ( you need the top of the Valve cool and the bottom of the Valve Hot to come apart )
Clean it all up in Gas > pull the plunger from the bottom . Blow dry the whole Valve and lubricate the plunger and reinstall. Work the plunger up and down to insure movement . Carefully instal the Top of the valve back together . You may need to heat the bottom of the valve again .
Naturally none of this is necessary if the valve is working . Or if your rich you can just buy a new valve lol
Hope this helps

 

Great info above. AAV probably just freed up with your usage and is now closing off the aux air. Easy solution is probably to open up the idle screw taking note of how much you turn it (so you don't introduce new variables that you can't return to their original state).

Idle should be a little high on cold startup, up to 1500 maybe. It should calm down to 750-800 when warm. 500 seems too low for these cars. North American 4.5 1973 should be 5 atdc with vacuum at 750 and the vacuum retard at idle is about 10 degrees. So if vacuum isn't working 5 btdc is where it's supposed to be.

Have you gone and fixed any vacuum leaks since your purchase? Vacuum leaks typically increase idle speed.

Oh.... I forgot... Points. Points wear down on these and timing retards as they wear. The gap also closes as the rider wears out. At higher rpm, the points will float and open longer. At lower rpm, the rider will ride smoothly along the cam and possibly never open the points, resulting in no spark. The first place is experienced this was at stop lights after the car was warm. In drive when car warm is when idle is lowest. Revving at stop lights increases points float and keeps points opening. So the higher idle at startup could be allowing some points float. Maybe you just need to re-gap your points.

 

I think the last post is right on the money. I'd look at vacuum leaks first, then check to see if everything on the carb is moving like it should. The recent servicing could've caused some debris to make it into the carb and cause something to get stuck or clogged. So, check vacuum hoses, then think about a potential carb servicing/ rebuild.

 

1973 450slc is fuel injected d-jetronic. No carb.

Easiest thing really is to make sure you've got spark. If you've got a timing light, you can put it on the ignition wires and crank the ignition to see if it lights up. But just as effective is to take the distributor cap off and check to see if the points open at the cam lobes.

 

Thanks for all your input! I will start working on it and give feedback!

The thing that confuses me the most is the idling after a cold start and dying out immediately after a fuel filter change. I put in a Bosch F5007 (equivalent with Mann WK818 OR Mahle KL4) one although there was a Knecht 626/3 fuel filter in it. Could this be the issue? A wrong new fuel filter? I punctured the old one to see how dirty it was, and it was ugly.

Before the fuel filter change the car didnt do the stalling after the engine warmed up.

I checked the lines after install and nothing is pinched or obstructed. I can post a cell phone video of the car running and dying. How do I do that on this forum?

If the responses remain as it is stated above, I will go into that direction immediately.

Idling rpm is definitely high reacting on what was said earlier.

Maybe not related to this current issue, is that I do have a suspicion about a vacuum leak somewhere. Idling is high right after startup and I don't like a particular sound the engine makes. It's a deeper almost clattering sound really good audible in the video when I'm next to the car.

 

. I can post a cell phone video of the car running and dying. How do I do that on this forum?

I post to YouTube, and then post the link here. It seems to automatically embed (if the link format is right).

Edit:
Have you taken off the distributor cap and taken a look at the points yet? Very quick and easy.

 

Solid lifters are louder and if the oiler tubes are clogged, then the cams will wear.

Hopefully your 73 still has the original metal-backed timing chain guides.

It's a very good idea to change the timing chain tensioner if you don't have any record of it being done. On startup, the TC tensioner only uses it's (tired old) spring to apply pressure to the chain before oil pressure builds and the oil pressure applies tension to the chain. This, coupled with old brittle plastic timing chain guides can be catastrophic.

 

the fuel filter number is 000 092 76 01 , the brand is not critical . if you are sure this problem happen just after replacing the filter , do it again , just to make sure , or test fuel pressure at the cold start valve connection .28 psi

 

Fuel filter isn't making any sense time as more fuel is generally used on startup than at warm idle. I suspect it is coincidental.

 

Congrats on the purchase! Please join the gang over at the R/C107 forum as we have a lot of stickies and other great informaiton available over there.

 

The Bosch replacement fuel filter part number on the box reads 0 450 905 007. I ordered a Knecht 626/3 and am waiting for it to get to me so I can get to the same situation. From there we will find out more! Thanks again for all great posts.

I'll let you guys know my progress!

I will dive into the c107 forum as well!

Ard

 

O'Reileys Auto parts has a fuel pressure Gauge


O'Reileys Auto parts has a Tool Loaner program that includes a Full pressure Gauge
So for free you can use their gauge and test your fuel pressure .
If you have a low reading at the Start Valve then test it just before the Pressure Regulator in case the " Pressure Regulator " got dirt in it or just went out . If you have good pressure in but none out replace it .
you need about 28 LBS

 

Here is the video of the car running and stalling after a couple of minutes.

I don't like that sharp noise audible best right next to the car in the video. (Sec 10-18 and mid 50's in the vid). Does anybody have a possible diagnosis?

 

What are the RPMs when the car is first started?

Have you turned the idle screw at all?

Have you checked the points?

It seems like the shutdown is fairly rapid from the video. I can't tell though. I believe you mention that it is starting to hesitate before it stalls.

 

Thinking more about this, I think after the car is warm you should diagnose this by determining whether you have no air, no fuel, or no spark.

 

after the car is warm you should diagnose this by determining whether you have no air, no fuel, or no spark.

Did you do this?

 

It took a while for the new fuel filter to arrive and today I installed the exact same fuel filter but guess what, the situation is still the same: it starts up, runs for about 5 min and dies the exact same way as in the video.

The points look good.

After just reading up and asking around more and talking about what was suggested here, could it be that the fuel pump relay is the cause?

After reading a lot from various things on this and the c107 forum, I found the relay box. I have 2 questions about this: there are 8 relays inside the box. There is a separate bracket attached on the both side walls of the relay box with 1 relay attached to that centered at the top half of the relay box and there is one more relay just outside the box. Can somebody tell me the function of all relays?

Would exchanging this fuel pump relay solve my problem?

How can you see/test that a relay is bad? Can you fix a bad relay?

Thanks in advance of all your help!

 

Following Advice

It took a while for the new fuel filter to arrive and today I installed the exact same fuel filter but guess what, the situation is still the same: it starts up, runs for about 5 min and dies the exact same way as in the video.

The points look good.

After just reading up and asking around more and talking about what was suggested here, could it be that the fuel pump relay is the cause?

After reading a lot from various things on this and the c107 forum, I found the relay box. I have 2 questions about this: there are 8 relays inside the box. There is a separate bracket attached on the both side walls of the relay box with 1 relay attached to that centered at the top half of the relay box and there is one more relay just outside the box. Can somebody tell me the function of all relays?

Would exchanging this fuel pump relay solve my problem?

How can you see/test that a relay is bad? Can you fix a bad relay?

Thanks in advance of all your help!

*************************
Your not letting people help you totally Let us help , A fuel Pressure test well tell you a LOT ' as before I suggested that you perform a Fuel pressure test , See previous posts as to how to do this at the Start valve to hook up the Gauge . Once you have done this it well tell you if your Fuel pump is working . It should have about 28 LBS . Leave the gauge on as you start the car and watch it . See what it say's when the car dies .
the gauge should hold pressure after the motor stops for some many minutes like up to 15 min's .
This well tell if your fuel pump is working or not the Gauge does not lie .
It well tell you if the " fuel Pressure Regulator " is working or not
( I Suspect this may be the problem by the way )
***************************************
points I believe your car has trigger Points so that means you have 5 Set's of points . One Set on the top of the Distributor under the cap set's at 0.14 exactly >> not 0.13 or 0.15 << you must remove the Distributor to see the Trigger points they slid out to service .
See this post for information on how to service the " Trigger Points "
http://www.benzworld.org/forums/vintage-mercedes-benz/2193385-w-108-4-5-staring-problem.html
a tool costs only $22 to set the points ( all 4 set's )
*****************************************
About your fuel " Pressure Regulator " if you fuel Pressure drops off after you start the car and it dies then attach the Gauge on the inlet side of the Fuel Pressure Regulator and test the Fuel Pressure . If you have good pressure before the regulator then you have your answer . Bad regulator .
*******************************************************
Dirty engine Bay > as I believe i mentioned every thing needs to be clean around all electrical having to do with your ignition . If Dirty clean it you may be surprised .
By the way it only take some 5 Min's to test the fuel Pressure

Hope this helps

 

Check the comprehensive illustrated d-jet thread for locations of each relay. You can just swap the relays.
http://www.benzworld.org/forums/r-c...comprehensive-illustrated-djet-72-75-350-a.html#/forumsite/20548/topics/1600137

It is possible that the relay is your problem, but the symptoms seem too consistent for FP failure in my opinion.

What do you mean when you say the point "look" ok?

 

My general thoughts after watching the YouTube video:

1) the sound on the right sounds like an exhaust leak. Also, This car has solid tappets that need to be adjusted regularly, and that could be related.

2) exhaust looks like you are burning oil, could be valve seals - how many miles?

3) after car is completely warm, what is idle set at? It seems low for cold start. As I recall, warm idle in this car should be something like 750.

4) replacing the filter would only allow an increase in fuel pressure. Perhaps you are now running rich, and when the AAV valve closes when you warm up, the engine dies due to over-rich mixture.

See if adjusting the mixture leaner helps.