Adjusted - Fuel Bypass Spring
 

I pulled the fuel check banjo on the IP yesterday, and found it at ~20.5 mm; stretched to ~27 mm and reinstalled.

https://i.imgur.com/UeD0nzf.jpg

how are the results?

I don't know yet, I still have to get it timed!

Good to hear! Its one of the first steps to achieving a smooth idle..

If you alter 2 things at the same time and you get an improvment you will not know which one caused the improvement.

Hey Diesel 911, I hear that, only I had no problem before; just couldn't get even a puff of initial power building smoke, and since I had the Injection Pump out to inspect the intermediate bearing/bushing, I figured I'd replace the primer pump, old cracking lines (w/tygon), and adjust the fuel bypass spring to spec. (I mostly noticed the lack of resistance in hand bleeding the fuel lines, and things just went from there!)

(I certainly know not to manipulate multiple variables and expect to get any kind of evidence of causative effect; unless, of course, I run a matrix of all of the variables! :P)

(P.S. Intermediate shaft turned out good by the way, with not even .05mm axial play.)

I took a look at the fuel bypass spring on the '83 617. It was at 20 mm. I stretched it out to 27mm and reinstalled. As I pumped the hand fuel pump to bleed the air it seemed to pressurize a lot more than before after a few strokes.

Test drove the car at 45 mph, then 60-65. It seemed to have only slightly more power.

It was easy enough to do, just have 14mm and 17mm wrenches to do the 15 min job.

I drove the car some more today and noticed one significant change. It idles smoothly when stopped in gear now.

Before this minor fix, I would usually move the gear selector from D to N at stop lights because it was not idling smoothly. Now it has the proper idle when in gear with the brakes on.

Thank you for this easy tip to improve the ride!

No worries, I'm glad I stumbled across it and the fix on here (Thanks WHunter!); it just seemed my system wouldn't build much pressure when bleeding. I got the motor fired up, and I have yet to take it for a spin, but I am really happy with the idle, as well as the smooth but quick return to idle.

(I also felt a lot of "seat-of-the-thumb difference" when pumping the system up! Dollars to Doughnuts this would effect folks' drip timing!)

May I ask where is it located on the IP?

It is on the side of the IP near the engine block, near the middle of the IP. There is a fuel line attached by the bolt. The line comes from the fuel filter.

The bolt has two hex-heads, a 17mm with a 14mm on top.

Take the bolt out of the IP and unscrew the top hex to remove the spring. Be careful not to loose the steel ball inside the bolt, under the spring.

Is my memory correct that this item is only there on turbo diesel cars, or do the N/A injection pumps have this same "adjustable" spring as it were?

All mercedes w123 diesels have them and others too....here is where it is located

http://www.peachparts.com/shopforum/...t-img_2826.jpg

Great. Thanks. I'll plan to check both of mine.