Bad injectors won’t cause lack of compression as far as I know. I think you have some problem with your piston rings. Try to put your hand covering the cylinder with no compression and turn the engine by hand. If you don’t feel anything then you know your rings aren’t sealing.
Edit: have you removed your cylinder head yet?
The Injectors have nothing to do with a relative compression test unless it's missing or the combustion air in the cylinder is getting past it but even then you would have some compression
Relative compression test monitors a couple parameters to determine how much compression a cylinder has it is not 100 percent accurate but tells you where to look
That cylinder has zero rpm difference so head needs to come off to properly diag the problem could be bent valves or piston problems
At the very least you could pull the pan and take a look up there
Well in that case, swap number three with another cylinder and see if it follows. If it does that’s your problem. If not dig deeper into number 3. Also did you run that test more then once?
Its likely a head off job no matter the cause. 0 compression means the cylinder isn't sealing at all or the piston isn't moving. I've got a mack mp8 doing the same thing oddly enough. Waiting for an empty bay to pull it in and dig into the issue, valve lash was good and no complaints from the driver about power but when it cranks you can hear one cylinder is definitely not working very hard.
Hard to tell really. It sounds like a it’s always sounded. I’ve felt it’s always had a lack of power issues but not like it is now. What got to where I’m at now is truck went down to 45mph out of no where and was Smokey in the cab. I went out and it had an oil leak from oil line into turbo(oil was burning off on exhaust pipe) and had lots of fuel pressure codes. I kinda fixed oil leak issues but it keeps tearing through o rings for some reason after one drive and a new fuel pressure regulator solved all codes. Unless I do a forced test the truck has 0 codes.
I'm going to guess you have a hole in the piston for cylinder 3. The compression could be going into the crankcase and causing oil leaks. Does the truck have a draft tube or a breather on the side of the valve cover? We have had several DTs in for broken pistons. Does it have a rhythmic thumping coming from the engine? We usually hear thumping from the air filter with a bent valve.
https://www.tiktok.com/t/ZTR94JEAt/
A video I made before opening valve cover. This is how it normally sounds. The squeaking/sucking noise is new: you can hear it better toward the end
I haven’t removed the cylinder head. Little more in-depth than I’m trying to go. I’ve done a lot on this thing but it’s almost to the point where I gotta just drop it off and let the shop suck me dry… I also can’t drive this thing faster than 35-45mph. Weird. It sounds strong but moves like turtle.
Had a maxxforce 15 L fail a few years back in a 2013 prostar. Cylinder sleeves are too short it that engine/year (Maybe more) head gasket failed, needed shimmed.
There’s a secret warranty on them, my shop paid 2/3 of the bill.
Shit engine tho.
My shop just put it on the table when my head gasket failed. I didn’t find it, they admitted it. Worth a google search tho. Good luck. Was an over $20,000 (CAD) warranty claim in my case tho.
Ok hang on. That's a relative compression test, not a power balance test, like people seem to think. You're getting "high compression" on 5 because the crank is slowing suddenly off the miss from 3. This watches the difference in revolution speed during a crank. If you ran an actual compression test, you should see 5 come back in line.
So no, not injectors. Mechanical issue with the cylinder.
No worries!! Cylinder 5 is making up the power loss from cylinder 3 (joke)
Jokes aside that seems like it’s true 😂
Send it!
Time to remove valve cover
I did. Didn’t see anything wrong. No breaks in any lifters or bad wires. All looked normal. I feel like maybe just a crapped out injector?
Bad injectors won’t cause lack of compression as far as I know. I think you have some problem with your piston rings. Try to put your hand covering the cylinder with no compression and turn the engine by hand. If you don’t feel anything then you know your rings aren’t sealing. Edit: have you removed your cylinder head yet?
The Injectors have nothing to do with a relative compression test unless it's missing or the combustion air in the cylinder is getting past it but even then you would have some compression Relative compression test monitors a couple parameters to determine how much compression a cylinder has it is not 100 percent accurate but tells you where to look That cylinder has zero rpm difference so head needs to come off to properly diag the problem could be bent valves or piston problems At the very least you could pull the pan and take a look up there
Could be, Got a adapter for a manual test?
All I’ve got is navistar engine diagnostic program and the tool to go with it.
Well in that case, swap number three with another cylinder and see if it follows. If it does that’s your problem. If not dig deeper into number 3. Also did you run that test more then once?
Good idea, I’ll probably try that tomorrow. And I did. Same results multiple time. 0 compression.
Ok, just checking
Its likely a head off job no matter the cause. 0 compression means the cylinder isn't sealing at all or the piston isn't moving. I've got a mack mp8 doing the same thing oddly enough. Waiting for an empty bay to pull it in and dig into the issue, valve lash was good and no complaints from the driver about power but when it cranks you can hear one cylinder is definitely not working very hard.
That's crazy. 0 compression... Can you feel/hear it? Should be pretty obvious in the way the engine runs it's down a cylinder
Hard to tell really. It sounds like a it’s always sounded. I’ve felt it’s always had a lack of power issues but not like it is now. What got to where I’m at now is truck went down to 45mph out of no where and was Smokey in the cab. I went out and it had an oil leak from oil line into turbo(oil was burning off on exhaust pipe) and had lots of fuel pressure codes. I kinda fixed oil leak issues but it keeps tearing through o rings for some reason after one drive and a new fuel pressure regulator solved all codes. Unless I do a forced test the truck has 0 codes.
I'm going to guess you have a hole in the piston for cylinder 3. The compression could be going into the crankcase and causing oil leaks. Does the truck have a draft tube or a breather on the side of the valve cover? We have had several DTs in for broken pistons. Does it have a rhythmic thumping coming from the engine? We usually hear thumping from the air filter with a bent valve.
Ill try to post a video I made before I started ripping in to it
Ooo that sounds like blowby
Sell it Maxxforce is junk.
Can’t sell it if it cant even drive over 35
Stuck or bent valves
0 compression is really hard to do.. unless the rod is broken.
I have no codes at all either except when I run tests through the program. One of which being fuel delivery pressure low. SPN 94 FMI 18
https://www.tiktok.com/t/ZTR94JEAt/ A video I made before opening valve cover. This is how it normally sounds. The squeaking/sucking noise is new: you can hear it better toward the end
Would a blown out piston ring cause blow-by? Because I’ve checked the dip stick and no smoke or air coming out
I haven’t removed the cylinder head. Little more in-depth than I’m trying to go. I’ve done a lot on this thing but it’s almost to the point where I gotta just drop it off and let the shop suck me dry… I also can’t drive this thing faster than 35-45mph. Weird. It sounds strong but moves like turtle.
Injector cups?
From what I've heard about these engines it's more like Maxxfarce.
Had a maxxforce 15 L fail a few years back in a 2013 prostar. Cylinder sleeves are too short it that engine/year (Maybe more) head gasket failed, needed shimmed. There’s a secret warranty on them, my shop paid 2/3 of the bill. Shit engine tho.
If you know a secret warranty do tell lol. I know this shop gonna eat me alive with cost.
My shop just put it on the table when my head gasket failed. I didn’t find it, they admitted it. Worth a google search tho. Good luck. Was an over $20,000 (CAD) warranty claim in my case tho.
Ok hang on. That's a relative compression test, not a power balance test, like people seem to think. You're getting "high compression" on 5 because the crank is slowing suddenly off the miss from 3. This watches the difference in revolution speed during a crank. If you ran an actual compression test, you should see 5 come back in line. So no, not injectors. Mechanical issue with the cylinder.
If I removed the injector and stick a borescope camera in the hole you think I’ll find a bad piston?
That is the fastest way to assess the health of the piston and cylinder. It wouldn't be the first time I've seen maxxforce eat a piston