My MB manual states diaphragms should be replaced with corresponding spring. I purchased a diaphragm from the Medford MB dealer but no spring was included - I count 3 different springs. Which one are they referring to?. After inspecting the new part was identical, I switched it out for the old, carefully installing the old parts. The engine runs poorly, issuing light smoke and the governor is hunting like I was blipping the throttle.
I have pulled the pump four times since, using the drip method and carefully aligning 26 btc, checking the pump gear scribe, compression check (all 300 lbs +) adjusted the valves, replaced injectors and it still runs terrible.
Because of the governor hunting, I suspect there is too much slack between the push rod and the diaphragm allowing it to pump with the vacume. The manual states the push rod should just touch the diaphragm and adjustment can be made via the nut on the piston in the governor chamber.
I'm assuming this is when the diaphragm is in it's rearward (stop position) but I don't know. Tough question but if anyone has a clue to offer, I would certainly appreciate it - my hands look like I'm wearing black gloves. Thanks!

 

From what I have read most People have been able to change only the Diaphragm with no issues.

What is missing is if you tested to see if there is a vacuum leak in the newly installed Diaphragm or the back Housing with the Lever on it.

It is common for the Housing to leak in the Lever Shaft area.

In the Manual there is instructions on how to do the test if you have the complete manual.

 

Thanks, Forced induction,
Apparently, I threw out the two compensating shims along with the old diaphgram - they must have been stuck. I'll crank it up again when I get enough courage.
Practice does make it a much quicker job compared to the first in & out of the pump and related gear. Thanks again for the post..