Variable valve timing - PeachParts Mercedes-Benz Forum

adrianruk · #1 08-23-2002, 06:32 PM

Is there an easy way of checking that the variable valve timing is working correctly? My 300TE-24 (3 ltr M104) does not seem to pull any better than my 300TE (3 ltr M103) until about 5000 rpm.
Can I safely unplug the solenoid connector?
Is the timing varied progressively or is it either in or out?
What voltage is applied to the solenoid by the CIS system? I'm wondering if I can rig up a bypass switch for test purposes.
Any help appreciated.
Thanks
Adrian

Gilly · #2 08-24-2002, 12:13 AM

Yes, you can test it by jumping power and ground to the solenoid with the engine running. You will here it click and also the engine at idle will run poorly, almost stalls. It's either on or off, not variable. If I'm not mistaken it's always provided power, the engine control unit will provide a ground when it wants it activated.

Gilly

Mick J · #3 08-24-2002, 04:19 PM

On my M111 engine you can sometimes see the oil pressure guage fluctuate when the timing changes - I think that's because the timing solenoid uses engine oil pressure to act hydraulically on the camshaft drive advance mechanism.

adrianruk · #4 08-24-2002, 06:22 PM

Many thanks Gilly & Mick
Tested it in the garage today - you were exactly right in all that you said Gilly. It certainly appears to be working. It operates at a no-load engine speed of about 1900 rpm - there is a slight change in engine note to accompany it.
I understand it cuts out again at a higher rpm but it didn't seem to up to about 4000 rpm (didn't want to rev it much higher off-load!). I'm sure it does cut out as it pulls like a train at high revs, its just at lower revs that it seems to lack the power I would expect.
As regards the oil pressure fluctuation I shall watch the gauge with interest in future, though I would be surpised if I saw anything - the oil pressure is always on maximum at anything over 800 rpm (despite its 197000 miles!).
Thanks again
Adrian

Gilly · #5 08-25-2002, 09:58 AM

Adrian:
Ther is one other possible problem, the cam position sensor. I'm sorry I can't quote how to test it without looking it up. It's the round black conector near the connection for the solenoid, on the side of the front chain cover. This picks up on a magnet on the side of the cam, I belive the control unit needs to see this signal to make the change to the position. I hope I'm right on this, usually these systems use the cam position for the ignition system, but I believe it's also used on this engine for the variable cam timing.

Gilly

puzzler · #6 03-11-2017, 05:09 PM

just want to add my notes here. I know its a long gone conversation..But the lower pin supplies 12V at all times and the continuity through the solenoid supplies 12 to the other wire and pin. The solenoid is activated by grounding the upper pin lead through the ECU it seems to me..Now MY question is how much magnetic force should result. I grounded the pin and no click in the cam. A very weak amperage seemed present and I sensed a very weak magnetism at the center of the coil instead ot the strong pull one might expect, say enough to make a washer stick tigltly to the coil....Im wanting to ask Pelican staff and looking for the right page for my question..