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Scubaseas · 13-03-2023, 09:50

Quote:

Originally Posted by JonathanC

This is an interesting thought and a line of thinking I'd not considered. Thank you for replying.
JC

There should be if memory serves. an insulating washer between the injector and the prechamber. If that's missing, you can get the noise you have. If I recall there are washer on either side of the prechamber. maybe one got lost during injector swaps or is jammed in the bore? Add one to see if it makes a difference in the noise.

Just FYI it usually good practice to replace the insulating washers when pulling the injectors. At least on Bosch auto and truck stuff.

I doubt it's a rod or wrist pin knock, Sounds too high and tinny to me. If there was a water ingress issue you should have sone other symptoms like overheating or oil emulsification or low oil pressure. Mechanics stethoscope would be a tool to use to aid in ruling the wrist pin or rod bearing out.

JonathanC · 13-03-2023, 10:01

Quote:

Originally Posted by Scubaseas

There should be if memory serves. an insulating washer between the injector and the prechamber. If that's missing, you can get the noise you have. If I recall there are washer on either side of the prechamber. maybe one got lost during injector swaps or is jammed in the bore? Add one to see if it makes a difference in the noise.

Just FYI it usually good practice to replace the insulating washers when pulling the injectors. At least on Bosch auto and truck stuff.

I doubt it's a rod or wrist pin knock, Sounds too high and tinny to me. If there was a water ingress issue you should have sone other symptoms like overheating or oil emulsification or low oil pressure. Mechanics stethoscope would be a tool to use to aid in ruling the wrist pin or rod bearing two out.

Thanks for the info...
I do have new packing and washer (along with O-Rings) I'll be putting in when I get the injectors back from the fuel shop this weekend. I will also inspect the Pre-Chamber area for anything weird looking.

From what the previous owner told me, it's been like since he owned it and since it quiets down at higher RPM, it never bothered him. He actually brought it down from the Pacific Northwest and motored for about 200 hours on it. I would think that if it was a Rod, it would have let go?

JC

SY Harmony · 13-03-2023, 11:21

Quote:

Originally Posted by JonathanC

Thanks for the info...
I do have new packing and washer (along with O-Rings) I'll be putting in when I get the injectors back from the fuel shop this weekend. I will also inspect the Pre-Chamber area for anything weird looking.

From what the previous owner told me, it's been like since he owned it and since it quiets down at higher RPM, it never bothered him. He actually brought it down from the Pacific Northwest and motored for about 200 hours on it. I would think that if it was a Rod, it would have let go?

JC

With the injector out, you should be able to pull the prechamber with a pick. Look for witness marks of it banging together and missing seals

Scubaseas · 13-03-2023, 11:31

Might want to put a screwdriver on the valves and see what kind of spring pressures you have. Captain Obvious would point out not to bend a valve while doing this.

Change the prechamber seals if you're going to pull them up. Easier said than done on some engines. Not familiar with replacing them in situ on your motor. Might be an easy job. Make sure there is no carbon ridges when you put the prechamber back in. If you do get them out stuff a borescope in and see if there are bang marks on top of the piston. Or heavy carbon build up.

SY Harmony · 13-03-2023, 11:33

Or nice steam cleaned appearance.

Scubaseas · 13-03-2023, 11:34

Quote:

Originally Posted by JonathanC

Thanks for the info...
I do have new packing and washer (along with O-Rings) I'll be putting in when I get the injectors back from the fuel shop this weekend. I will also inspect the Pre-Chamber area for anything weird looking.

From what the previous owner told me, it's been like since he owned it and since it quiets down at higher RPM, it never bothered him. He actually brought it down from the Pacific Northwest and motored for about 200 hours on it. I would think that if it was a Rod, it would have let go?

JC

I would think a large end rod bearing would fail in less than 200 hours. Wrist pin or piston slap can go on a long time without failure. I wouldn't be overly concerned about the noise but it is a bit more than others think is proper. There has to be some reason for it. Do you have to fix it? Not until it breaks I suppose.

Scubaseas · 13-03-2023, 11:41

Quote:

Originally Posted by SY Harmony

Or nice steam cleaned appearance.

Indeed. Comparative analysis between cylinders would also be helpful.

There are other ways to check for water intrusion. If he's got the injectors out put a radiator tester on the (make sure it's full) cooling system, pump to 12PSI or so and let sit overnight. See if there's any coolant in the cylinders the next day. Putting the cooling system under pressure for 12 hours is an excellent way to check for a head gasket or cylinder head leak.

JonathanC · 13-03-2023, 12:44

Quote:

Originally Posted by Scubaseas

Indeed. Comparative analysis between cylinders would also be helpful.

There are other ways to check for water intrusion. If he's got the injectors out put a radiator tester on the (make sure it's full) cooling system, pump to 12PSI or so and let sit overnight. See if there's any coolant in the cylinders the next day. Putting the cooling system under pressure for 12 hours is an excellent way to check for a head gasket or cylinder head leak.

I have an compression tester adapter (dummy injector) on order. With that I'll be able to do a compression test and also a leak down test to check for issues.
JC

JonathanC · 13-03-2023, 12:47

Quote:

Originally Posted by Scubaseas

Might want to put a screwdriver on the valves and see what kind of spring pressures you have. Captain Obvious would point out not to bend a valve while doing this.

Change the prechamber seals if you're going to pull them up. Easier said than done on some engines. Not familiar with replacing them in situ on your motor. Might be an easy job. Make sure there is no carbon ridges when you put the prechamber back in. If you do get them out stuff a borescope in and see if there are bang marks on top of the piston. Or heavy carbon build up.

This scenario has me really thinking... and I'm going to dig in to it before I put the injectors back in. A question that comes up in my head is: I thought the injectors rested and seated on packing and washer that are on top of the pre-combustion chamber? If there as any play, would the injector have been loose? I'm walking through the tear down in my head... thoughts?

JonathanC · 13-03-2023, 12:49

Hey all...
I cannot express my appreciation enough, to all the thoughtful and insightful responses.
Thanks so much...
JC

SY Harmony · 13-03-2023, 12:56

Quote:

Originally Posted by JonathanC

This scenario has me really thinking... and I'm going to dig in to it before I put the injectors back in. A question that comes up in my head is: I thought the injectors rested and seated on packing and washer that are on top of the pre-combustion chamber? If there as any play, would the injector have been loose? I'm walking through the tear down in my head... thoughts?

Yes and no, the injector holds the prechamber in compression with the copper washer. But, cylinder pressure is a crap ton greater than what you can wiggle by hand. It may have been a little loose, but honestly, i doubt it.

The Jeep 4.0 is notorious for piston slap lasting 100k miles.

kenbo · 13-03-2023, 13:16

From what I hear in the two videos it seems to me to be either valve train noise on the #1 cylinder exhaust valve ONLY or piston slap. The exhaust valve is under compression when the decompression lever is engaged taking out any valve train slop and when the fuel load is removed the noise goes away taking away the force that would cause the piston slap.

I'd run it with the valve cover off to rule out or in the valve train and I'm not sure pulling the head will rule out piston slap but you may see some evidence on the cylinder wall at the bottom of the stroke. Good luck and let us know what you find.

BTW that's the smoothest running 3 cylinder engine I've ever heard running on 2 cylinders. The compression test should be revealing.

JonathanC · 13-03-2023, 13:17

Quote:

Originally Posted by SY Harmony

Yes and no, the injector holds the prechamber in compression with the copper washer. But, cylinder pressure is a crap ton greater than what you can wiggle by hand. It may have been a little loose, but honestly, i doubt it.

The Jeep 4.0 is notorious for piston slap lasting 100k miles.

Oh Yes, very familiar with the 4.0 piston slap. Most often caused by heat soaked injectors. I insulated all of the injectors on our last 4.0 and all but solved it unless very hot days and you shut off the Jeep and then restart it while still hot.

JC

Scubaseas · 13-03-2023, 13:35

Quote:

Originally Posted by JonathanC

I have an compression tester adapter (dummy injector) on order. With that I'll be able to do a compression test and also a leak down test to check for issues.
JC

You will need a source of compressed air to do the leak down test. Just FYI.