so should i leave the engine off. Loosen one, see if the idle is less rough, if not then tighten and try on all 4?

or do i loosen while the engine is running?

Is the engine shaking a lot or is it a loud banging like a jackhammer? If the latter you may have a collapsed motor mount.

Still sounds like glow related issue to me.....could be wiring to glows.

Take precautions for fuel spillage....but disconnect while running... it will be immediate... loosen... observe.... tighten... do next one...

Fuel pressure is likely low.
Common problem with 240D om 616 motors.

Pull the lift pump regulator spring and stretch it to 27mm.

I don't see a mention of valve adjustments. ..

A compression test is still warranted... As low fuel pressure causes #1 injector to dribble and wears out the cylinder. .. so, you could be looking at a low compression first cylinder.

where is the lift pump regulator spring? and which nut?

if you are looking at the manual pump, is it the bolt to the left or right of that manual hand pump? Once removed do i just take the spring inside and stretch it to 27mm measuring with a ruler (stretch by hand)?

It's the fuel pressure regulator banjo on the back of your injection pump towards the engine block. Some of the newer models didn't get a modular valve, they were crimped shut.
Best bet is to hit up Greazer for his upgraded spring rate spring, it will bring your fuel pressure back up and keep the system full of fuel at all times during the cycle.

He said he did a valve adjustment and asked earlier in the thread if he should do it again

its an 82' 240d.

not sure if has the modular valve or not. What would it look like?

i have uploaded images to this post. What am i loosening? not sure how to measure this spring size (or where this spring is?)

-- Thanks

2mrrxV.jpg, image 4. The feed line from the secondary filter to the ip housing
the banjo fitting mounting to the inner or back side of the ip, remove fastener
with 17mm wrench do not lose both soft washers on either side of banjo fitting.
once free from fuel line, steady with 17mm use 14mm to remove spring and ball
from hollow bolt, stretch small spring slightly to 27mm reinstall tighten and reassemble (stretching allows for a smoother more consistent fuel supply to the ip
allowing smoother idling) the spring being ancient will lose its tension over time
so consider greazzers replacement option.

best of luck.

ok so i figured out the bolt (on the back). THe problem is the entire bolt comes off (not just the top part?) It is really really REALLY stuck on there. Is this crimped on possibly? (hence i would need to buy an entire new bolt?)


after reading hte post above.. i can get that bolt off.. but i have no idea how to loosen that top part of the bolt to get to the spring inside??

ok fixed the spring. It is now 27mm. But.... still the idle is vibrating the same (wayyyy to much).

I guess i should try a compression test/removing injectors one at a time?

Do you have a Gorilla Knob on your dash ?

Whats a gorilla knob? The idle adjust is all the way up (high rpm)