Checked injection timing, just about died laughing - OM606 content - PeachParts Mercedes-Benz Forum

bsmuwk · #1 02-28-2017, 11:03 PM

97 E300 - OM606.912 - 280K miles

I bought this car some 2 odd years ago and brought it up to snuff. Has a few cross country trips under it's belt (all on the blog) and has overall done pretty well...albeit, being fairly asthmatic and somewhat smokey all the time. I didn't get any service records for the thing, but from the autocheck report - some 8 owners and 3 tiny accidents - I'm not expecting much lol The car is just a beater for me, even with it's AMG interior, body kit, suspension and brakes.......

I just about redid the entire fuel system, just never cared to check injection timing. Well, it's stormy out tonight, have nothing better to do and nobody's car to work on, so I decided to take the ole girl apart a bit and check out where she's at timing wise.

I about fell over from laughter. Freaking thing made it to the top of Pikes Peak (barely) like this!

Factory should be 14* ATDC with the tool. We're at 2* BTDC here.

I'll stick an order in for some IP seals with my weekly MB order. I'll take an hour out of my day and yank the pump out, reseal it and stick it where it should be. I've never taken the valve cover off, at this point, I'm afraid to haha

tyl604 · #2 03-01-2017, 08:50 AM

What is that Positionsgeber thing? A tool to find TDC? Interested to hear how it runs after adjustment.

Diseasel300 · #3 03-01-2017, 09:51 AM

That is the A/B timing light. On IP's with the RIV tang, that tool tells when the IP is at its reference timing, which should be ~14˚ATDC on the OM60x engines.

It's amazing how well these engines run with even major blunders in timing. My SDL came to me with the IP 1 full revolution out of time (crankshaft 360˚ out of time) and still ran (albeit poorly)

tjts1 · #4 03-01-2017, 10:16 AM

Quote:

Originally Posted by Diseasel300

That is the A/B timing light. On IP's with the RIV tang, that tool tells when the IP is at its reference timing, which should be ~14˚ATDC on the OM60x engines.

It's amazing how well these engines run with even major blunders in timing. My SDL came to me with the IP 1 full revolution out of time (crankshaft 360˚ out of time) and still ran (albeit poorly)

Injection timing within its allowed range of adjustment is not nearly as critical as some people make it out to be. Its mostly for emissions. These injection pumps can't even adjust timing based on RPM, load or temperature.

Zulfiqar · #5 03-01-2017, 11:06 AM

There is one very "gotcha" item in this whole setup. The pointer scale for the harmonic balancer is actually moveable over a range of about 15 or 20 degrees. This can throw you off mark quite a lot.

Its quite a lengthy process to get it to show true TDC at 0 mark as you need to remove the prechamber first and use a dial indicator. I beleive one can make a piston stop and do it the old fashioned way to find exact dead zero TDC like on all other engines - but MB say do not rotate the engine backwards.

86-300sdl · #6 03-01-2017, 11:19 AM

Quote:

Originally Posted by Zulfiqar

There is one very "gotcha" item in this whole setup. The pointer scale for the harmonic balancer is actually moveable over a range of about 15 or 20 degrees. This can throw you off mark quite a lot.

Its quite a lengthy process to get it to show true TDC at 0 mark as you need to remove the prechamber first and use a dial indicator. I beleive one can make a piston stop and do it the old fashioned way to find exact dead zero TDC like on all other engines - but MB say do not rotate the engine backwards.

I'm glad you mentioned the movable scale pointer. Some five years ago I was replacing the water pump, vacuum pump and so on...accidentally loosened the bolt holding the pointer in place...it moved...haven't been able to use it to reference timing since. Guess I'll wait to set it when it's head gasket R&R time.

bsmuwk · #7 03-01-2017, 08:18 PM

Quote:

Originally Posted by Zulfiqar

There is one very "gotcha" item in this whole setup. The pointer scale for the harmonic balancer is actually moveable over a range of about 15 or 20 degrees. This can throw you off mark quite a lot.

Its quite a lengthy process to get it to show true TDC at 0 mark as you need to remove the prechamber first and use a dial indicator. I beleive one can make a piston stop and do it the old fashioned way to find exact dead zero TDC like on all other engines - but MB say do not rotate the engine backwards.

Yup! In addition, there's always a huge possibility the damper actually shifted on itself, moving the timing markers on the damper itself in relation to crankshaft.

Luckily on this engine, the damper position isn't shifted and I know the pointer is in the correct position. So we're effectively 2* BTDC on this motor. I think before I actually make it a point to adjust it, I'll whip the camera with mic out and take cold start videos of how it sounds/revs before and after. Still funny and would explain why the car struggled so much in altitude with injection timing so far advanced