Dear All
I am helping a Pagoda-friend, who is not technically capable, with his late 230SL.
Car runs pretty ok, but cold start is very poor!
I have checked the following:
- Cold start electrical system works - it opens the cold start valve (CSV) a few seconds. But I am not able to check, if the CSV actually sprays fuel - but it seems so, based on the smell after repeated cold start attempts.
- All ignition cables checks out ok with resistances between 0.9-1.1 kOhm.
- Ignition adjustment was on the mark, and the car pulls nicely in all revs, as far as I could feel.
- The car currently has an original Bosch 0 231 185 009 JFU6 distributor (dizzy) with new points, combined with the green Bosch ignition coil and a 0.9 Ohm pre-resistance, which seems to be the standard configuration in a 230SL, as far as I can see (I have two 280SL myself and are not fully familiar with the 230SL on the ignition conf.).
- Spark plugs (NGK BP7ES) are all mixed black / while, and one is very black, indicating uneven fuel delivery by the fuel injection pump (FIP).
- Idle warm fuel mixture was 9.5% CO, and I adjusted it down to 6.5%. But there are problems with the idle fuel mixture screw, which is difficult to operate, and I did not dare turn it more than this.
My initial conclusions are as follows:
- FIP need to be taken out and bench calibrated, and the issue with the idle fuel mixture screw fixed. Though this may first happen after the season is over, and in the meantime a counter-action should be taken to improve the cold start.
- The NGK BP7ES spark plugs should be replaced with some warmer plugs. Try first with NGK BP6ES plugs and see if they can keep the plugs cleaner. If not, try BP5ES plugs instead.
- As it seems the ignition is weak at cold start, I am thinking that a stronger red Bosch ignition coil + a 1.8 Ohm pre-resistance can be used instead of the current green one.
What do you think of these counter-measures? Can we use a red coil in a 230SL with a standard 230SL Bosch dizzy?
Are there other things you would try, to improve the cold start under the current condition of the FIP?
Looking forward to hear your views on this.
Cheers,
Christian
