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Hi all,
I have a 2007 m6 black on black with a little over 90k miles. It spun a bearing so i decided to rebuild the entire engine. Including new piston rings, main and rod bearings, vanos pump rebuild, and so on...
Putting everything back together went well besides the tricky timing set procedure. There is close to no info how to set the timing on the s85 engines. I set it and used the timing check procedure and it looks spot on.

After engine was done i go to start it and it cranks over, catches around 500rpm, then dies and spins from the starter. I tried the DME CAS sync procedure but it doesnt help and i doubt it will because i am not getting any codes. I did get a vanos oil pressure code once so i removed both vanos lines, put them in cans, cranked engine, and they instantly filled with oil. So my problem isnt the vanos pump. Something strange i did notice was the passenger exhaust camshaft is very jumpy when cranking the engine. I was thinking maybe the vanos adjuster unit is leaking so its making the camshaft bounce and not let it run. I changed and it its still the same. No start, Just cranking barely to 500RPM. I have even changed the starter thinking it was weak and still the same. Could it be a shutdown of the injectors for whatever reason?? I get no codes in Ista except for transmission adaptation because i changed clutch and slave cylinder but to continue the procedure it says to start the engine. Any help or tips would help. Thanks
Dmitry
 

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If absolutely everything else is right... my guess is flywheel installed wrong. The S85 is the only engine that I know of that allows the flywheel to be clocked in something other than the correct orientation. You need an optional dowel to make sure it goes in the right orientation if memory is right. WTF were they thinking...
 

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Check fuel and spark. You may also want to verify compression, that helps confirm timing. There’s a counterbore on the crank for the through dowel, I’d assume you indexed that properly when you rebolted it back on. You can check that by looking for the skip at the sensor and looking where TDC is.
 

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If absolutely everything else is right... my guess is flywheel installed wrong. The S85 is the only engine that I know of that allows the flywheel to be clocked in something other than the correct orientation. You need an optional dowel to make sure it goes in the right orientation if memory is right. WTF were they thinking...
Removed transmission and checked the pin in the crank. All lined up
 

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Check fuel and spark. You may also want to verify compression, that helps confirm timing. There’s a counterbore on the crank for the through dowel, I’d assume you indexed that properly when you rebolted it back on. You can check that by looking for the skip at the sensor and looking where TDC is.
I got spark. How do i check if injectors are opening? Compression was a bit weird. both sides were showing 60psi and after a few cranks, drivers side of the engine was showing 160PSI. Im assuming this was just the vanos adjusters being bleeded?
 

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How are you checking spark, specifically, that it’s firing on the ignition cycle of the proper cylinder.

You’re seeing that cylinder pressure for each cylinder on each bank respectively? 160 is good, 60 is really bad. What was done/replaced on the respective heads? Seems you should see where the air is leaking, you may have a partially open valves or bad cylinder head sealing. it could be timing is off by a few degrees. VANOS should have nothing to do with it since default timing with none of the actuators engaged should be spot on. It could be that the actuators weren’t set right. you could have bent valves from incorrect timing or if it was a replacement head, they were already damaged.

The compression variation needs to be addressed otherwise the engine will never run correctly.
Once thats addressed, check fuel pressure first, you can view pressure with INPA or ISTA, it’s a function under the DME.

check fuel pressure first, you can view pressure with INPA or ISTA, it’s a function under the DME. since you had the engine out, there will be air in the fuel line, and it will take several crank cycles for the injectors to open and fuel pressure to bleed out the air. You can check injector opening by back probing the wire connector on the harness and looking for the pulse. This might not register on a DMM, especially a cheap one. A scope would be better and if you have an inductive pick up that would eliminate fussing with back probing. You can also remove the injector tree and look for fuel to shoot out on a rag.

also just to get an idea, how many engines have you rebuilt before? Only asking to be more efficient in replies. Also if you ask the mod to move this thread to the E60 M5 section you will get more people there since hardly anyone goes to the M6 area.
 

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How are you checking spark, specifically, that it’s firing on the ignition cycle of the proper cylinder.

You’re seeing that cylinder pressure for each cylinder on each bank respectively? 160 is good, 60 is really bad. What was done/replaced on the respective heads? Seems you should see where the air is leaking, you may have a partially open valves or bad cylinder head sealing. it could be timing is off by a few degrees. VANOS should have nothing to do with it since default timing with none of the actuators engaged should be spot on. It could be that the actuators weren’t set right. you could have bent valves from incorrect timing or if it was a replacement head, they were already damaged.

The compression variation needs to be addressed otherwise the engine will never run correctly.
Once thats addressed, check fuel pressure first, you can view pressure with INPA or ISTA, it’s a function under the DME.

check fuel pressure first, you can view pressure with INPA or ISTA, it’s a function under the DME. since you had the engine out, there will be air in the fuel line, and it will take several crank cycles for the injectors to open and fuel pressure to bleed out the air. You can check injector opening by back probing the wire connector on the harness and looking for the pulse. This might not register on a DMM, especially a cheap one. A scope would be better and if you have an inductive pick up that would eliminate fussing with back probing. You can also remove the injector tree and look for fuel to shoot out on a rag.

also just to get an idea, how many engines have you rebuilt before? Only asking to be more efficient in replies. Also if you ask the mod to move this thread to the E60 M5 section you will get more people there since hardly anyone goes to the M6 area.
I check spark with the spark plugs out and connected to the coils. how do i know that its firing on the ignition cycle?
All the intake and exhaust valves have been compound lapped with a perfect seal. New Stem seals. A few new lifters that gave out, and new head gaskets torqued to spec. Im still leaning on the vanos adjusters because it was difficult to figure out but i set and re checked the timing 3 times already. Ill check the fuel pressure but i was confused how that would work because there is no pressure sensor on or around the rail nor is there a shrader valve to check it like the 6cyl ones. Ill fire up ista and see what it says.
I have rebuild an audi 2.0tfsi engine in the past. Did multiple head gasket jobs on e60s and ive done a stem seal job on an n62 545i. As well as rebuilt a transmission for a 07 328i.
Thanks for the help, I really appreciate it!
 

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Ok great to know, the stock stem seals seem to be junk. there is a built in pressure transducer that measures line pressure in the driver side wheel well. The only way to get to it is pull the wheel liner but no need, they don’t really fail. Yes there’s no schrader. The tree connectes to the stainless line with a 3/8” quick release, you can just put a hose on that into a bottle and key on and that should force most of the air out of the line.

the fuel pressure can be read under ECU functions button when you have the DME highlighted in ISTA. I seem to remember spec is 6 bar, 3-4 bar min.

I think if the security conditions are not met the DME will not open the injectors, but fuel pressure will exist and it will crank. Pretty much the same BMW routine.
 

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“how do i know that its firing on the ignition cycle?”

I assume the S85 doesn’t do wasted spark, if it does, it’s gonna spark every 360 deg instead of 720 doing this doesn’t matter unless it’s sparking at the 180.

The way to figure this out I s kinda hard, the only way I know this can be done is with a 2+ channel scope. One channel on one of the coils (prolly cyl 1) to log and see the waveform collapse indicating spark discharge, the other channel on crank sensor. This channel will show every impulse on the reluctor, you have to do some math and plot tracing to figure out the what the pulses correlate to the 720 deg of the cycle. You have to figure out where the skip in the reluctor ring is in relation to cyl 1 TDC. If you have a 4 channel, hooking up to the next 2 in the firing order helps you figure it out slot quicker.

I assume the S85 doesn’t do wasted spark, if it does, it’s gonna spark every 360 deg instead of 720 doing this doesn’t matter unless it’s sparking at the 180.

hopefully it’s just that the fuel pressure hadn’t built up yet, but the big swing in cylinder pressure is still worry some.
 
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