OM 606 idle miss and excessive blue smoke

zeeman

06-09-2020, 10:39 AM #11

X Double Dot
zeeman
X Double Dot FWIW, as we seem to have a similar issues, albeit it could be caused by a number of things, on my way to pulling my prechambers I did a (cold) compression test the other night and repopped my injectors. While the number consistencies seemed reasonably close to what they should be, i did notice that my number 4 injector would start to pee a stream of fuel at 1900psi if I approached the pop pressure slowly. I'm going to replace that nozzle and see if it helps.

I also noticed that i was getting some leakage out of the injector return barbs. I know they are there for a reason, but does anyone have an idea how much is expected? my understanding is that this is from leakage internal to the injector on the non sealed surfaces, but that said, if the IP is sending a metered amount of fuel, there shouldn't be a ton coming out of these lines or the injector wouldn't be getting the proper injection qty correct?

Still waiting on my prechamber tool, but i'll post up any findings if/when I do get them out.

injector # - compression test (psi) - injector pop (psi)
1- 365 - 1975
2- 380 - 2025
3- 375 - 2010
4- 380 - 1980
5- 385 - 1990
6- 365 - 2020

haven't seen a compression test spec, but these seem to be a reasonable range and close to what most people are seeing. The injector range is 1958 - 2030psi from what I've seen.
When your pop pressure test, there should not be much if anything coming out of the return barbs. I would check your mating surfaces the injector body and nozzle seal washer. The pop off pressure could stand to be a little more uniform, Usually 25 PSI difference between them is the norm. When the engine is running the return hoses bleed off the excess fuel and relieves the delivery valve when the injector closes. Check your prechambers for cracks when you get them out if you have had a injector dripping. I had one come apart in the cylinder and it was not pretty, engine rebuild time.

yeah it kind of made me suspicious that i need to lap the internal parts. I've certainly seen what i thought was a decent amount flow out of the return hoses when I first started it up the last time (watched as the air bubbles got pushed around). The injector bodies didn't leak at least.

b/c it didn't really "drip" until right before it would pop open i don't think I was getting alot of extra fuel out of that injector, nonetheless though I'll certainly look for cracks when i get it apart

What happens it will drip after the engine is shut off onto a hot prehamber and cause it to fail after some time. The return line from the injectors to the fuel filter will have fuel coming out of it when it is running, under low pressure.

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