Prechamber Ball - Page 5 - PeachParts Mercedes-Benz Forum

Lucas · #61 05-20-2015, 02:32 PM

Quote:

Originally Posted by OM617YOTA

The glow plugs could have been replaced with no one knowing about the prechamber condition. Maybe the injectors were bad too and were also replaced and no one checked prechamber condition then either?

Interested in seeing what you find.

Edit: By golly I had no clue USB boroscopes were so inexpensive.

Good point. Your injectors may have been replaced since as well. Since your glowplugs looked fine.

I'm having this battle with Nissan. My car had a noisy injector. I kept saying it was a big deal, they didn't believe me. Well it was #2. And #2 burnt a rod bearing and the piston.

They just had to put a new motor in, and did all new injectors....

mach4 · #62 05-20-2015, 05:30 PM

After rebuilding my prechamber extraction tool to accommodate the larger 5/8" 5# slide hammer in the AutoZone tool loaner program, I got #3 prechamber out. It had no ball in it. It was really tight in there - so much so that I thought it was catching on something.

Here are the set of prechambers front and back side-by-side.

I popped the injectors with the following results

#1 1850# good
#2 1850# good (some occasional streaming under lower pressure)
#3 1800# good
#4 1850# good
#5 1850# good

I'd say that these are as good as or almost as good as the ones I have in the car right now - very close.

I have no explanation of the apparent increasing severity of the erosion of the ball going from 1 to 5. #1 appears completely normal.

I'm beginning to imagine a scenario where the car began starting hard (maybe to the point where ether was used routinely), running really poorly and the owner elected to install new glow plugs and new injectors, only to find it still ran poorly. Not wanting to put more money into it, just elected to junk it.

When I tested the engine prior to purchase, my only criteria was that it ran. I was not terribly sensitive to how well as I knew I could most likely time it, replace injectors and glow plugs and get it up to spec. I was trying to protect myself against a skipped/broken chain, ultra poor compression, or something catastrophic that would make it a known bad engine. So when it ran, idled and revved up, that's all I was focused on. Given the condition of the prechambers, it's likely it was running on the glow plugs as I just had them connected directly to the battery for the duration of the test.

I'm kind of disappointed that I don't apparently have a spare engine ready to go, but for the $400 I paid for the engine and transmission I'm definitely good. I've already used the transmission and the starter, easily worth the price of admission.

HappyHappy · #63 05-20-2015, 05:45 PM

Quote:

Originally Posted by mach4

After rebuilding my prechamber extraction tool to accommodate the larger 5/8" 5# slide hammer in the AutoZone tool loaner program, I got #3 prechamber out. It had no ball in it. It was really tight in there - so much so that I thought it was catching on something.

Here are the set of prechambers front and back side-by-side.

I popped the injectors with the following results

#1 1850# good
#2 1850# good (some occasional streaming under lower pressure)
#3 1800# good
#4 1850# good
#5 1850# good

I'd say that these are as good as or almost as good as the ones I have in the car right now - very close.

I have no explanation of the apparent increasing severity of the erosion of the ball going from 1 to 5. #1 appears completely normal.

I'm beginning to imagine a scenario where the car began starting hard (maybe to the point where ether was used routinely), running really poorly and the owner elected to install new glow plugs and new injectors, only to find it still ran poorly. Not wanting to put more money into it, just elected to junk it.

When I tested the engine prior to purchase, my only criteria was that it ran. I was not terribly sensitive to how well as I knew I could most likely time it, replace injectors and glow plugs and get it up to spec. I was trying to protect myself against a skipped/broken chain, ultra poor compression, or something catastrophic that would make it a known bad engine. So when it ran, idled and revved up, that's all I was focused on. Given the condition of the prechambers, it's likely it was running on the glow plugs as I just had them connected directly to the battery for the duration of the test.

I'm kind of disappointed that I don't apparently have a spare engine ready to go, but for the $400 I paid for the engine and transmission I'm definitely good. I've already used the transmission and the starter, easily worth the price of admission.

It is a very interesting fact pattern that seems hard to understand other than something like this explanation. Does really answer anything as to the actual causative events that resulted in the facts before us, but I don't think you'll ever be able to figure that out without learn something about the POs and the engine's history. Kind of freaky in that stuff like this happening can give one nightmares! I was looking t the picture of erosion in the cylinder head and started thinking about the times I've seen and others have posted seeing something escaping from the area's surrounding injectors and pre chambers. Now when I think about that happening I'll also keep in mind "Maybe the pre chamber is being disintegrated into the side of the cylinder head!!!!!"

HappyHappy · #64 05-20-2015, 05:48 PM

plus, any difference in the size of the pre chamber tip holes between those that have balls and those that don't?

And is it an optical illusion that the #3 pre chamber looks slightly longer and with a more rounded tip on it?

dude99 · #65 05-20-2015, 05:53 PM

It looks more rounded to me as well

mach4 · #66 05-20-2015, 06:09 PM

Quote:

Originally Posted by HappyHappy

And is it an optical illusion that the #3 pre chamber looks slightly longer and with a more rounded tip on it?

Good catch! No it's not an optical illusion.

Quote:

Originally Posted by dude99

It looks more rounded to me as well

And it is more rounded.

They're all stamped 617/03

Not sure what all that means other than someone was in there presumably trying to fix something...

Maxbumpo · #67 05-21-2015, 11:08 AM

The head may or may not be toast, but the rest of the engine should be fine. Spray some preservative wax/oil into it, seal it all up and stick back into storage.

OM617YOTA · #68 05-21-2015, 11:15 AM

I think a better course of action would be to boroscope or yank the head and verify that the rest of the engine is indeed fine before sticking it in storage and relying on it as a spare.

I can attest to how much it SUCKS to go through a lengthy install time for an engine just to have it fall apart.

Lucas · #69 05-21-2015, 11:51 AM

Quote:

Originally Posted by HappyHappy

plus, any difference in the size of the pre chamber tip holes between those that have balls and those that don't?

And is it an optical illusion that the #3 pre chamber looks slightly longer and with a more rounded tip on it?

I'm vaguely remembering an update to the design. From 3 hole to 5 hole.

I mentioned this before but the fsm says they are wear items.

mach4 · #70 05-21-2015, 12:13 PM

Quote:

Originally Posted by Maxbumpo

The head may or may not be toast, but the rest of the engine should be fine. Spray some preservative wax/oil into it, seal it all up and stick back into storage.

I think the current course of action is to do a valve adjustment, then do a compression check and then pull the head and see what I've got.

One possible snag with that scenario is that I've used the good starter off the spare engine and I'm not about to pull it off the car just to do a compression check. I'm hoping that there's enough life left in the "bad" one to spin the engine enough with only one cylinder under compression to get some decent results.

I'm digging the optimism, but not allowing my hopes to get up too high.

I'd rather not waste a set of prechamber seals on a compression check on a potentially bad head/engine. Do you think I'll be ok with reusing the seals for that process - maybe an ultra thin coat of RTV or gasket sealer for the test?

OM617YOTA · #71 05-21-2015, 12:31 PM

Try it! You're not going to be heat cycling or dealing with combustion pressures. Maybe put some soapy water on them while testing to see if there are leaks.

winmutt · #72 05-21-2015, 12:33 PM

Luckily the bottom of the prechambers was all in tact and did not look like this:

mach4 · #73 05-21-2015, 12:43 PM

Quote:

Originally Posted by winmutt

Luckily the bottom of the prechambers was all in tact and did not look like this...

Indeed!

BillGrissom · #74 05-21-2015, 01:38 PM

Interesting. Someone might calculate the volume of the missing pre-chamber ball. It must certainly add TDC volume and thus lower compression ratio. Low compression for some might be due to a vaporized ball, rather than worn rings. I always use the injector hole for compression measurement, in which case it is easy to peer down and verify each pre-chamber still has its ball intact. By the same token, always insure your compression fitting occupies the same volume as the injector did. My kit has a ring you must install to insure that.

DeliveryValve · #75 05-21-2015, 08:18 PM

Hey M4,

Did you pull the ball out of that chewed up prechamber to see what it looks like?