240D prechamber differences
 

I have a large glow plug '77 240D. One cylinder makes more of a knocking sound than the others. I isolated it to #1 cylinder by loosening each inj. line one at a time. I tried another injector and no difference. It is NOT an engine mechanical issue. It is a combustion issue. I have read that a cracked
prechamber can be a cause. I have one out of a later 240D head that had the small pencil type glow plugs. Can I use that prechamber in the earlier head??

You need to match the pre-chamber to the type of pistons installed in the block. Do you have access to the FSM?

I'm pretty sure the hole for the glow plug in the Prechamber is larger on the older heads.
before you condemn the PC, pull the injector and look inside for a damaged ball...

keep in mind that the #1 cylinder sub fuel pressure issue is common on the 240... do a compression check first and see if it's lower than the rest...

Be careful here as there are other possibilities. How long has this issue been there in miles? If the noise gets worse or is getting worse do not use the engine or I would not.

The number one rod bearing may be badly worn but has not turned yet. Could be an easy fix at this point. The chances of that condition existing in my opinion are good enough to consider it as a possibility. I estimate that 90 percent of rod bearing failures and the heaviest wear on bearings on the 616 engines occur on the first cylinder.

Sure pull the injector as it has been out reciently anyways and visually check that prechamber. If it does not turn out to be the issue get back and suggestions will be made by a few members..

I am not quite certain how you where able to determine it is not a mechanical issue at this point. When the number one cylinder is involved with knocking noises is both not unusual and consitantly a potential possible issue on the 616 engines.

Then again it may just be a prechamber or first cylinders injection pump element out of sequential timing. The only thing that I am certain of in what you describe. Do not ignore the potential of what that bearing could result in if it is the issue and you continue to drive on it. Plastigauge is your friend. .

No you can not use the newer pre chambers in yours. They will fit but will hit the piston. And they do not have the correct spray pattern for your pistons. I have some spares if you do really need one. As the others have said look at the ball and see if it is still attached, if so it should be ok, if not then it needs to be replaced.