450 SL in Denmark

Hi Peter,

wrong injector pulses would affect mixture - meaning A/F ratio - but not vacuum level. Pistons moving down create vacuumwhen exhaust valves are closed and intake valves are open. If air can comes from another source, vacuum level will be low too.

So sealings under injector are a source, but injectors are not.

Well, I finally got around to pull the valve covers off - initially to adjust the valves. Before I got that far I went to check the timing chain. Here I discovered that the chain has either stretched or maybe even jumped a tooth as the timing marks on the cam do not line up with the TDC mark on the crank pulley. I think that I may have found the culprit of the low engine vacuum. It seems indeed that the valves and the pistons are not playing the same accord at the same time.

The first picture is of the RH cam with the crank pulley at TDC and where the timing marks do not line up. The second is the same place but with timing marks lining up at the cam but now the crank pulley is several degrees retarded.

Best, Peter

Hi Peter,

well that is of course a reason for wrong valve timing and vacuum. Did you not tell that you have been to a garage to look after your car? They should have checked that.

Now check chaing guides whether they are broken. You should still have steel guides. Those you can continue to use. If they are plastic, replace them. Then insert a new chain. If a tooth jumped over, it means 18° difference. You should also replace chain tightener.

BTW I received my ECU back and also another nice package. I say thank a lot you and will test soon. I am a bit tight in time as I had a lot to do and will now go for a motorbike tour in Alsace.

I’m glad to hear that both items arrived safely. The original steel guides are unfortunately no longer there, so it must have had a chain job done in the past. I wish you a good trip to Alsace. I myself are going to Munich tomorrow morning for my personal inauguration to the Bavarian Oktoberfest.

Best, Peter

Hi Peter,

have fub on Oktoberfest and do not forget your leather trousers (Krachlederne) ! I hope that you have a reserved table.

Good morning everyone,

The weather here in DK is nice so I took the Merc for an early run for the first time this season and I am still experiencing that the engine jerks/sputters under acceleration. When giving it some more throttle it evens out (for the better but not 100%) and begins to run more evenly. Under full throttle there is no problem and when cruising at 80-90 km/h it also runs OK. At idle at operating temperature it sputters/phuffs from the exhaust and it smells of gasoline.

When it is cold and during warm-up (while driving) there are no symptoms whatsoever - it seems to only show when the engine has reached full operating temperature.

Since it apparently is temperature sensitive I have checked the air and coolant temp sensors to see what ohm they read when warm:

Air = 180 ohm at 28 degrees and 340 ohm at 17 degrees
Coolant = 230 ohm at 90 degrees (operating temp)

Ignition has been checked and verified. Dwell at 30 degrees and timing at idle is 5 degree ATDC and absolute timing also OK. New NGK BP5ES spark plugs and BERU ZEF406 wires.

Fuel pressure is exactly 2 bar. I've also done a leak test to verify if the/some of the injectors are stuck open. It shows a fuel pressure of 1.8 bar after 20 minutes i.e. a loss of 0.2 bar. That should be OK.

The trigger points have been adjusted using Norberts tool. 

The potentiometer on the ECU is turned completely to the lean side (counter clockwise seen from the mounting position) and remember that it is still running rich also at idle. It have no ability to make a CO reading, but I am quite sure it is running rich.  

Any ideas?

Best, Peter