(11-27-2018, 03:09 AM)zeeman First run of a used engine in my latest conversion. Engine was noisy, sounded like a piston knock. Then it started missing.
Ran a compression check, number 5 had hardly any compression. Pulled head off and this is what I found, the prechamber had failed. Anyone have an idea what caused this?

(11-29-2018, 08:03 AM)jav1 I'm no expert but #4 seems wetter than 6 or 3 as well?

(11-29-2018, 04:08 PM)jav1 Ouch!  Sorry man- that's a lot of extra work. Kanda makes me want to replace my nozzles now... just in case.

(11-29-2018, 09:40 AM)atypicalguy

(11-27-2018, 03:09 AM)zeeman First run of a used engine in my latest conversion. Engine was noisy, sounded like a piston knock. Then it started missing.
Ran a compression check, number 5 had hardly any compression. Pulled head off and this is what I found, the prechamber had failed. Anyone have an idea what caused this?

yes it is liquid fuel dripping onto the prechamber when the prechamber is glowing. Those prechamber tips get extremely hot and they cannot handle the rapid cooling. So if the injector starts to leak, the tip eventually falls off the prechamber and dances around inside the cylinder, which doesn't have any room for that sort of thing.

(12-08-2018, 08:21 AM)atypicalguy Hard to build a business on motors of unclear provenance. Unless it was my car, I would pull the head and measure and inspect everything before installing. Pay me now, pay me later. People can handle expected expenses better than unexpected ones.

(12-10-2018, 12:58 PM)maneyc91 Well i had a little laugh to myself when i saw this thread, I came here to make a thread about my prechamber failure and found this instead, with pictures that could have been from my motor they look so similar, cylinder #5 for me too. I was driving along and it just went downhill real fast, smoking, sputtering etc. No comp on cyl number 5, smoking out the intake ports. From what i could see its an injector problem. The bummer is mine happened about 2 weeks after i finished doing a mech pump swap, big turbo etc. My plan of approach is to pull motor, swap in a good piston and rod, get the valves for #5 worked on, smooth out the damage on the head, put 'er back together. Luckily my holset hx35 didnt get damaged by the metal chunks. Probably going to pull my motor later today.....

editt:: my damage is actually isolated to just the #5 so i guess i got lucky there, my motor still has all its crosshatching after 200k

(12-12-2018, 01:25 PM)jav1 did you find a source for prechambers?

(12-12-2018, 01:08 PM)zeeman

(12-10-2018, 12:58 PM)maneyc91 Well i had a little laugh to myself when i saw this thread, I came here to make a thread about my prechamber failure and found this instead, with pictures that could have been from my motor they look so similar, cylinder #5 for me too. I was driving along and it just went downhill real fast, smoking, sputtering etc. No comp on cyl number 5, smoking out the intake ports. From what i could see its an injector problem. The bummer is mine happened about 2 weeks after i finished doing a mech pump swap, big turbo etc. My plan of approach is to pull motor, swap in a good piston and rod, get the valves for #5 worked on, smooth out the damage on the head, put 'er back together. Luckily my holset hx35 didnt get damaged by the metal chunks. Probably going to pull my motor later today.....

editt:: my damage is actually isolated to just the #5 so i guess i got lucky there, my motor still has all its crosshatching after 200k

The number 5 cylinder seems to be the problem cylinder. You might also want to do the Diesel Meken thermostat bypass to number 5 cylinder as well. He has a you-tube video on this, I do this to all my conversion engines. DieselpumpUK also just came out with a smaller water pump pulley to run the water pump faster to improve cooling.

(12-15-2018, 12:52 AM)atypicalguy

(12-12-2018, 01:08 PM)zeeman

(12-10-2018, 12:58 PM)maneyc91 Well i had a little laugh to myself when i saw this thread, I came here to make a thread about my prechamber failure and found this instead, with pictures that could have been from my motor they look so similar, cylinder #5 for me too. I was driving along and it just went downhill real fast, smoking, sputtering etc. No comp on cyl number 5, smoking out the intake ports. From what i could see its an injector problem. The bummer is mine happened about 2 weeks after i finished doing a mech pump swap, big turbo etc. My plan of approach is to pull motor, swap in a good piston and rod, get the valves for #5 worked on, smooth out the damage on the head, put 'er back together. Luckily my holset hx35 didnt get damaged by the metal chunks. Probably going to pull my motor later today.....

editt:: my damage is actually isolated to just the #5 so i guess i got lucky there, my motor still has all its crosshatching after 200k

The number 5 cylinder seems to be the problem cylinder. You might also want to do the Diesel Meken thermostat bypass to number 5 cylinder as well. He has a you-tube video on this, I do this to all my conversion engines. DieselpumpUK also just came out with a smaller water pump pulley to run the water pump faster to improve cooling.

If it is an injector issue then why would coolant flow affect anything? Doesnt make sense. Unless injectors fail from poor coolant flow.

(12-15-2018, 09:58 PM)maneyc91 Well my motor and tranny are sitting on the floor next to the car, im waiting on a new piston and rod, just going to swap it in and hope for the best. Gotta have some valve work done too obviously. If I cant get a prechamber after going through all this I dont even know what i ll do. If i see an unsuspecting e300 in the wild they will not be safe.      I assume that anything that was assembled by MB and working properly should be left alone as far as inside the motor? Im a pretty good wrench btw, my e36 has a 347 stroker, 76mm turbo,DIYmegasquirt and 8.8 IRS rear end all done by me.

Ill look into that coolant bypass....

(12-15-2018, 09:58 PM)maneyc91 Well my motor and tranny are sitting on the floor next to the car, im waiting on a new piston and rod, just going to swap it in and hope for the best. Gotta have some valve work done too obviously. If I cant get a prechamber after going through all this I dont even know what i ll do. If i see an unsuspecting e300 in the wild they will not be safe.      I assume that anything that was assembled by MB and working properly should be left alone as far as inside the motor? Im a pretty good wrench btw, my e36 has a 347 stroker, 76mm turbo,DIYmegasquirt and 8.8 IRS rear end all done by me.

Ill look into that coolant bypass....

(12-21-2018, 10:53 PM)maneyc91 Hows your repair going? ive been slacking a little this week, got my exhaust manifold off the head, and cleaned up the face of my head on the bad cylinder, been looking around for parts, just got my piston in yesterday. Still bummed about the whole ordeal but whatever, life sucks get a helmet. Im really tempted to (mercedes drop in) v8 swap this w210 while the motors out and toss this om606 in my real favorite, an e36.

also quick question, can the ball pein in the prechamber fit through the top of the prechamber? When i did not know how they worked and first pulled my injectors I vac'd out the holes and inside the hole because 200k worth of crap fell in, a little bb was stuck on the end of my vac and i went huh weird and cast it aside. It was probably from #5 which broke off but i paid such little attention to it at the time. Not sure how to look inside the others to see if the balls there. If blown out with compressed air do i need to worry about knocking a ball out?

(12-23-2018, 11:41 AM)zeeman

(12-21-2018, 10:53 PM)maneyc91 Hows your repair going? ive been slacking a little this week, got my exhaust manifold off the head, and cleaned up the face of my head on the bad cylinder, been looking around for parts, just got my piston in yesterday. Still bummed about the whole ordeal but whatever, life sucks get a helmet. Im really tempted to (mercedes drop in) v8 swap this w210 while the motors out and toss this om606 in my real favorite, an e36.

also quick question, can the ball pein in the prechamber fit through the top of the prechamber? When i did not know how they worked and first pulled my injectors I vac'd out the holes and inside the hole because 200k worth of crap fell in, a little bb was stuck on the end of my vac and i went huh weird and cast it aside. It was probably from #5 which broke off but i paid such little attention to it at the time. Not sure how to look inside the others to see if the balls there. If blown out with compressed air do i need to worry about knocking a ball out?

Just got a set of NPR pistons from Germany, and took the block over to the machinest yesterday. I had to make a tool to get the piston cooling nozzles out so it could be bored.
Make sure you check the bore taper, even though there is still crosshatch in the bore the wear is at the top of the cylinder.
The ball on the tube in the prechamber can break off to and fit through the prechamber. Another failure of the prechamber. Make sure you check inside of all the prechambers.


Where did you get your prechamber? i ve been getting a refund and email saying they dont make them anymore from everywhere i ve tried.

(02-10-2019, 08:29 PM)maneyc91

(12-23-2018, 11:41 AM)zeeman

(12-21-2018, 10:53 PM)maneyc91 Hows your repair going? ive been slacking a little this week, got my exhaust manifold off the head, and cleaned up the face of my head on the bad cylinder, been looking around for parts, just got my piston in yesterday. Still bummed about the whole ordeal but whatever, life sucks get a helmet. Im really tempted to (mercedes drop in) v8 swap this w210 while the motors out and toss this om606 in my real favorite, an e36.

also quick question, can the ball pein in the prechamber fit through the top of the prechamber? When i did not know how they worked and first pulled my injectors I vac'd out the holes and inside the hole because 200k worth of crap fell in, a little bb was stuck on the end of my vac and i went huh weird and cast it aside. It was probably from #5 which broke off but i paid such little attention to it at the time. Not sure how to look inside the others to see if the balls there. If blown out with compressed air do i need to worry about knocking a ball out?

Just got a set of NPR pistons from Germany, and took the block over to the machinest yesterday. I had to make a tool to get the piston cooling nozzles out so it could be bored.
Make sure you check the bore taper, even though there is still crosshatch in the bore the wear is at the top of the cylinder.
The ball on the tube in the prechamber can break off to and fit through the prechamber. Another failure of the prechamber. Make sure you check inside of all the prechambers.


Where did you get your prechamber? i ve been getting a refund and email saying they dont make them anymore from everywhere i ve tried.

(02-15-2019, 02:49 PM)zeeman You might try E-Bay UK for some used ones. I managed to get one from the extra head I had. All the rest of the pre-chambers were okay upon inspection.

(02-16-2019, 01:35 PM)maneyc91

(02-15-2019, 02:49 PM)zeeman You might try E-Bay UK for some used ones. I managed to get one from the extra head I had. All the rest of the pre-chambers were okay upon inspection.

If i fixed all the stuff just to not be able to get a prechamber i might just lose it.