Very rich running and white smoke - 1973 450 SL R107 DJet

Hi All

Feeling very lost chasing a very rich running condition and white smoke from the exhaust on my 1973 r107 450 SL DJet



Smoke tends to be worse upon first start up once warm and then reduces (but still present). Plugs are black (sooty dry plugs)

• Fuel pressure is just below two bar and both air temp and coolant sensor are providing correct resistance readings.
• Map Sensor is holding the correct pressure however looks like it has been tampered with previously (see below pictures) 
• Timing has been checked. 7° BTDC is marked. For some reason when running can only see this mark at 18° mark. However timing is set to 7° BTDC without vaccume (noticed no change in timing when the vacuum line was added. Breaker plate is moving when mightyvac is used)
• Vacuum Smoke Test has been done recently and leaking parts replaced
• The injectors look original and are all firing
• Distributor - When chasing this problem last year, I listened to the injectors and realised 4/8 were not firing. This led me to the trigger points. I replaced some of the blocks and reset all dwell to 120-130 degree range. All injectors are now ticking.
• Can’t see any contaminants in oil
• No loss of coolant or blowback/bubbling in coolant reservoir

Feel it's being massively overfueled. It's been two years chasing this issue since i imported the car, and just want to be able to enjoy it now. Any guidance or diagnostic help is much appreciated! 

Nick





 

Hi Unknown,

we would appreciate if you could sign with fristname so that we can politely address you.

White smoke sounds like ATF. You will find a steel vacuum line from engine to gear box that modulates switching of gears. The actuator there can leak ATF to engine and then you will have huge white smoke clouds from exhaust. Test by removing that vacuum pipe from gear box and close ist.

Hi Dr-Djet,

I will check, however does this also mean i'll be burning rich? The smoke smells (and stings!) like fuel.

Thanks,
Nick

Hi Nick,

Too much fuel should rather make black smoke. But if it stinks fuel, then MPS, water temperature sensor and cold start valve are first candidates to look for.

Hi Nick,

Someone has likely tampered with your MAP sensor. From the factory there is a black cap, but this is now removed and it looks like someone has messed with the screw. That is usually bad news, but sadly not uncommon with US origin cars. Try to locate a “virgin” specimen with the part number 0280100100 that fits your car. Have you checked whether the cold start valve is leaking or stuck open?

Setting timing on your engine should be done with vacuum and then it should be 5 degrees ATDC. You describe that there is no difference with it plugged or unplugged. This suggests a broken vacuum can. The car will still run, but not optimal. I don’t believe it has any effect on your rich running condition. Have you tried measuring your CO values?

Best, Peter