Rebuilt S50 B32 Starting Issues

Post Mon Oct 19, 2009 2:39 pm

Hi,

Now I know this isn't an engine swap as the engine is now back in my M Coupe, but I thought the more technical minded may be able to help out.

I spun a main shell on no. 3 rod/cylinder back in march and have been rebuilding and tidying the car up since. As far as I can see the engine is back together fine and everything is connected up. However, the car does/will not idle, it turns over fine with no nasty nashing sounds and can run if you massage the throttle pedal but it sounds really rough like the timing is well out or it is missing. All 6 plugs and coils are emitting a spark and the cam and crank angle sensors are giving out the correct resistances.

Can anyone offer any advice to the cause?

Cheers in advance,

Paul

Post Mon Oct 19, 2009 3:07 pm

If the timing was out, you would have had the valves and pistons greeting each other by now..

Was the lump pulled then split to rebuild?

Post Mon Oct 19, 2009 3:09 pm

Is it timed up properly? Assuming you removed the crank for a regrind?

Post Mon Oct 19, 2009 4:01 pm

If you time these up wrong the valves meet the pistons.. So I would say it is timed correctly

Post Mon Oct 19, 2009 4:41 pm

No contact as yet. Phil Crouch from CPC came to my house and refitted the cams and the vanos with the correct tooling, so I'm 99.9% sure it is timed correctly. The block was fully stripped with crank regrind and new over size (+0.25mm) big end shells.

Cheers,

Paul

Post Mon Oct 19, 2009 7:29 pm

Have you definitely plugged all the sensors in and correctly?

Post Mon Oct 19, 2009 7:55 pm

you've connected all the sensors and pipework underneath the plenum correctly?

Post Tue Oct 20, 2009 11:05 am

I've checked all of the vanos and timing connectors and have felt that all of the plenum connectors are correctly installed. I have also by-passed the fuel pump relay and the pump seems to be working fine purging the system. Shall I remove the plenum properly and do a more thorough inspection?

Cheers,

Paul

Post Tue Oct 20, 2009 11:15 am

It would be a good place to start yes..

Post Tue Oct 20, 2009 2:15 pm

I'll do that when I get home this evening, although again I really don't think I missed anything off.

Could the double vanos unit cause this problem if the solenoids are not working or if there isn't enough oil pressure to get the splined pistons to move into the correct starting position?

Cheers,

Paul

Post Tue Oct 20, 2009 6:19 pm

Wav wrote:I'll do that when I get home this evening, although again I really don't think I missed anything off.

Could the double vanos unit cause this problem if the solenoids are not working or if there isn't enough oil pressure to get the splined pistons to move into the correct starting position?

Cheers,

Paul

hello paul,
i'm no expert on the vanos systems but, i believe they default back to 'easy starting' position when the engine is stopped? thats what the accumulator is for?

Post Tue Oct 20, 2009 6:58 pm

Generally with variable valve timing, when the vanos is 'off' (low oil pressure) it is in timing position, so low rpm setting

Post Wed Oct 21, 2009 10:04 am

Thanks for the advice guys. So if say the exhaust splined piston was pushed in too far (i.e. not fully retracted into the vanos housing) then only a small amount of oil pressure is required to push it back to give the correct start timing? And high pressure oil is what's required to get it to start advancing, pushing forward, at high rpms?

I think if this is the case then I can't see it being the vanos unit, I think it has to be something electrical... if all plug connectors are in correctly and all the sensors check out then maybe I damaged the wiring loom...hmm.

Ta,

Paul

Post Wed Oct 21, 2009 12:30 pm

I've just spoken with Phil Crouch and he is now begining to think that it could be down to a faulty vanos issue, assuming there are no big air leaks.

VANOS
So to clarify. When the pistons/splines are fully back into the VANOS housing that gives the maximum retardation of the CAMS relative to the crank. When the pistons/splines are fully forward, into the CAMS, that gives maximum advance of the CAMS relative to the crank.

If this is correct, what should be the exact position of the inlet and exhaust cams relative to the crank/sprockets in starting mode? Are there any documents stating the correct starting advace/retard angle of the cams at crank TDC or other?

Cheers,

Paul

Post Wed Oct 21, 2009 2:01 pm

With the crank at TDC, whip the cam cover off and there are timing marks on the cams and the cam housing.. Check they are lining up..

Post Wed Oct 21, 2009 2:02 pm

Cam timing marks are at the front, viewed from the back of the engine if that makes any sense..

Post Wed Oct 21, 2009 2:48 pm

Yep, it makes perfect sense. I've got the vanos installation and timing manual on my computer and having read through it a couple of times it is starting to sink in.

Will take timing cover off at the weekend to check, although in the manual it states that the starting vanos position is NOT the fully retracted position..

"When the engine is switched off, VANOS moves the
camshafts to a position which is advantageous to engine
starting. The camshaft timing is "not" permitted to be adjusted
in this position. The camshafts must be turned back to their
initial position."

so I assume the markings on the cams are not going to line up if it is in the correct start position?

Ta,

Paul

Post Wed Oct 21, 2009 4:05 pm

I would say that they moved to their correct start position when you turn the ignition on.. How else could you time them correct?

Post Sat Oct 24, 2009 4:46 pm

Managed to get it running on Friday with the help of Phil Crouch and his diagnostic kit. Turns out there were no wiring problems or any other faults, however the fuel injectors I had sent off for refurbishment... out of 6 two of them were jammed shut. After a few taps with a hammer and a drift we got the engine running pretty smoothly. Still have a small miss-fire, but other than that it runs really smooth.

Thanks for all the advice,

Paul