hard start!!!

[autoshop302]

i know this is a common concern and lots of question,,, a little history first.. My Boss  bought car a few years ago , its a 67 sl250..  ran great first year or ownership..no concerns... started warm or cold perfectly.. had the engine rebuild,(engine noise) trans , injection pump injectors, basically every thing was new or rebuilt on the engine and trans, I'm talking complete!! local Benz "expert",, he is very knowledgeable on the car and such, cost huge money to get done.. I myself am a lic tech for over 30 years, first time working on one of these, large learning  curve to say the least, I have gone over and adjusted everything possible 2 0r three times, however after a hot soak, say 40 min after driving, when trying to start, it cranks and cranks, gas, no gas, half throttle, nothing seems to work,, when it does start, its "loaded" up and I must rev up to clear , lots of black smoke, starting really rich.. I have adjusted every adjustment possible.. . when it does start it and clears out it purrs like a kitten, ideals 900rpm,runs down road perfecto, hesitations, stalling nothing I mean perfect!  but this damn long crank hot soak start is driving me crazy!!!any direction would be great, 

Rob..

[mrfatboy]

Have you tried disconnecting the starting/fuel enrichment solenoid? This solenoid enrichens the FIP at all temps when the engine is cranked.

There is lots written about it on this forum.

[Peter]

CSV is leaking or gets current also above 35 degrees C and floods the engine.
Testing see Technical Manual.

[autoshop302]

thanks for the help, yes I disconnected the sol at the pump.. I have had the csv apart, reset the seat, tested seems ok .. there is a 1 sec voltage at the csv when first crank and then its gone,, thinking of capping fuel line to csv for testing , to see if uit makes a difference, I have gone through all the testing in manual... I did pull the small 1/4 inch plug at the csv to see if there is fuel, and there was a a little drip at first and then nothing... if  disconnecting csv fuel line for testing and it solves the concern, is it advisable to leave disconnected? rthe car is only driven maybe 1 time a week in the summer, less then 500 km a year only in warm weather..

Thanks again..

[Peter]

I would not disconnect the fuel line, I would like to understand the problem.

If the engine is > 35°C is the CSV then still opening when you start the engine? If so, this could explain the issue.

[Cees Klumper]

Could it be the coil is going bad, when warm/hot? Check spark when starting hot.

[Taleb]

it happened with my w111 , I dismantled the thermostat on top of FIP it was full of water salt over the years I cleaned it properly and now running perfect .

[ja17]

Make sure the starting solenoid on the injection pump works every time the starter is energized. Make sure your fuel pressure and volume is correct. Fuel must flow through the system and back to the tank so that the fuel cools and does not boil in the system when the engine is hot. I agree, try disconnecting some starting aids, one at a time (just for diagnostic purposes) to see if the system is flooding.

[autoshop302]

So ,, just a update.. I have installed electronic ignition from pertronix,, (nice and simple kit, don't need to worry about the points now). removed and capped off fuel line to  csv to make  sure it was not leaking into the intake. disconnected wires from pump as a test as mentioned above, started right up drove around runs like a top, allowed to hot soak for 45 min,, no start long crank, really hard to start, it will start after trying for about 10 trys(cranking for 15 sec each time),, and then once started, runs like a top again!,, everything on car is new or rebuilt,  I have ordered a new coil, maybe bad when it gets hot?
one thing I forgot to mention, was the plugs were always fuel fouled! not one or two but all six, that's why I was thinking fuel concern,, now thinking lack of good spark..will keep ya up to date,, feel free to leave some more suggestions...

[mrfatboy]

What type of plugs do you have in there now?

[autoshop302]

I have tried diffent heat ,, right now I have ngk bp6e
have tried champion rn9yc
tried autolite 63
and also ngk bpe5

all have same concern.. after a long run I check the plugs and they are prerfect,, the only foul after hot soak..

[mrfatboy]

You said all the injectors are new.  Did you test them? Could they be leaking down during/after the hot soak? However, I find it hard to believe all are bad. 

I'm just throwing out ideas at this point.

[autoshop302]

Thanks everyone for the help.. now that every thing is set and adjusted, I think I have it figured out..i had a verity of   problems,, I went back over all the starting tests, tested csv for voltage, while cranking all good, warmed up engine let sit for 45 min retested, no power!.. installed ground to time switch in the intake, grounds relay, started right up,, after further testing I discovered this car has the optional time relay, for starting , should supply 12 volts to csv on every start for 1 sec,,, guess what nothing!,, took apart to check using info from this forum. The contacts were stuck open all the time,  cleaned adjusted , now works perfect!.. the confusing part was the plugs were always fouled, so I assumed it was over fueling,, I am guessing all the other things that weren't adjust properly all stacked up to this concern!! I will drive for a few days, and report back... on another note , if I want to buy new one I cant find one anyplace!  am thinking on adding a digital adjustable relay, in its place..