89 300sel

[Izrealromo]

Hey I am new to forums and I have got a 1989 300sel I am having problems getting it to pass emissions tested due to it running rich it’s in good condition and drives well besides the fact occasionally it’ll lung or boggle at acceleration as well as it won’t start the first crank but second or third I have read about it here and there but no definitive answer was wondering if I could get some help I’m new to Mercedes and am trying to learn

I’ve used a spark plug test light to make sure no misfire and it is good I’ve gotten a new fuel pump and filter but no avail as well as a new ignition coil

I read that there could be a leak or faulty cold start injector so I disconnected the fuel line to only the cold start injector only change is it made it harder to start

Any help is greatly appreciated

[Sugar Bear]

I'd be looking at loss of fuel pressure while sitting, try cycling the fuel pump on and off after it shuts off by itself 3 times before cranking.

Bad valve seals can cause this by fouling the spark plug insulators toward one side only, pull the plugs and have a look. The fouling on the insulator absorbs the fuel requiring 2-3 attempts at starting and then a stumbling idle for a few seconds.

[agillot1947@gmail.com]

Been out of this for awhile , retired , but you need to be able to read the on / off ratio at pin 3 of diagnostic socket . You cannot find those handy testers anymore , but a dvom that can read dwell in % , or just dwell and have a chart that convert angle dwell to % . with the engine warm , in closed loop , you adjust that % signal at 50% at idle or 2000 rpm . The oxygen sensor need to work . You adjust at the mixture screw of the CIS .