Checking timing on M103?
 

How can I check the timing on an M103 motor?
Factory spec should be 9deg at idle right?

I have a timing light, but not sure how to use it exactly.

Thanks guys.

Ah spotted the marks on the crank pulley....

Looks like its reading 19deg at idle :confused: Isn't it supposed to be ~9deg @ 650rpm?
Its somewhat difficult to tell though...I spot a 10 mark, but not the next notch -- does the pulley go: -10, 0, 10, 20 etc...? So could I have been technically spotting a -10 making it a -1deg retard?
Either way though, its definitely -1deg, or +19deg so it doesn't quite seem right?

Does that seem very wrong or is it just me?
For reference: I DO have that R16/1 timing resistor plugged in. It has not been removed.

I used this as reference too:
http://www.w124-zone.com/downloads/p...Timing/spr.JPG

Yes, it does have minus/negative marks. Once in a land far away I carefully checked TDC with the head off against the damper marks and the little tang.
As I remember, it was off a bit, but can't recall which way - big help Huh?

But, the system works off the rear crank position sensor, not the front one, and it's all adjusted electronically. So, in theory, timing should not be a problem; nothing to move or wear.

Of course, the cam can get retarded due to chain stretch; but tht won't affect the crank timing.

DG

So then for my low power issue I should probably get the crank @ TDC and make sure the cam is aligned in the correct position too (the hole and line lined up?)

Worth verifying the cam is timed right. Just a thought on the timing. How about the hose running to the ignition module on the driver's wheel well. It is supposed to affect the timing when vacuum is sensed. Should this be on or off when checking the timing?

Yeah, always good to verify the cam position; but....
- highly unlikely a 103 chain will stretch enough in 200k miles to appreciably affect cam timing (very rugged) - unless it's been worked on and reassembled wrong.
- still gotta find that exact piston TDC, and not knowing exactly where the damper/tab marks should align makes it a bit of a guess. The best way is to use a piston stop and go forwards-measure, backwards-measure, like when degreeing a new cam. But, I don't think the experts recommend turning a 103engine backwards, as it really stresses the chain tensioner.

I glanced thru the book, and the timing spec for the 103 at idle is 7-11 with the vacuum line either attached or plugged. Easy to check, though, just check the timing and then plug it and see if it changes.

One commet, years ago I did unplug my resistor, and the timing at idle did not change. It also didn't change at 2500 RPM in neutral. I assume it might cause a difference under load.
Comment - I left the resistor in and switched to regular fuel about 12 years ago - zero issues.

DG

When I was testing out different trim resistors for my turbo install I found that they all idled at the same timing 8-9 degrees. They were all pretty close at 2000 RPM without load. To simulate load at 2k I pulled the vacuum line from the EZL. That's where you see the difference. I measured a 10 degree spread between the different value trim resistors with a simulated load.

FWIW 750 ohm is stock for our US cars and it tested nearly identical to an open circuit (resistor removed) at the points where I was testing.

I suggested it because IIRC, the head was off this engine recently. I could be wrong because PS2CHO has been working on both of his W124s and I know one of them had a cylinder head refresh. I would agree, chain stretch wouldn't impact cam timing enough for it to be felt on acceleration.

I had the head off my 300TE, so not the engine I am dealing with.

Chain stretch on 95k mi engine is unlikely wouldn't you say so?

I would agree. Chain stretch has no doubt occurred but it would be measured in microns ;-)

From my own experience I can relate that my 88 300E Daily Driver has been a dog for most of its life. Interestingly it never suffered the dreaded EHA failure until it got to 290k miles late this past fall. I replaced plenty of parts trying to get better acceleration but never found the cause until replacing the EHA.

I had replaced two on the wife's 89 300E and never had to adjust them. But when I put the new EHA on the '88 I never thought to adjust it and didn't. The car woke up! It would chirp the tires on the third gear shift at WOT! It also, however was running too rich and overheated a cat.

I had always attributed the difference between the '89's strong acceleration to the dogginess of the '88 to the '89's low mileage (115k vs 290k at the time for the 88). But it was fuel that made the difference.

Although I believe you have gone through much of the fuel system if not all of it and have adjusted your EHA, I would suggest richening it all up to see what the reaction is.