I have a 1989/90 Merecedes Benz 500 SE, and all the time since I purchased it the car has had a starting-problem. When it is cold or it has been stopped for 15 minutes or so, it takes up to 10 seconds before it fires properly enough to start. Then it starts on 6 or 7 cylinders and runs roughly for another 10-15 seconds before it starts to run smooth on all 8 cylinders. If I turn off the ignition when the engine has already started, and then try to start imediately, - vrrom!! it goes right away. The performance is 100% when it is already running, - there is only this starting-problem. Any ideas?

jaypee@organizer.net

It sounds to me that you have leaking injectors. The column of fuel between the distributor and injector must be maintained while shut down. If the injector leaks, that cylinder or cylinders doesn't get fuel or gets it in too lean proportions for a period.

Since CIS injectors are fairly cheap (not exactly sure what you have with that model), its probably cheaper to replace them than to pay for diagnosis to find the culprit.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Thanks a lot for your answer. Here is some additional information that maybe can be useful: The fuelpump/filter/valve are all brand new. When I turn on the ignition, I hear the fuelpump starts, - and it never stops! Shouldn´t it when the pressure is right? Further, - when I turn the key to start the engine, it fires right away (maybe on 1 or two cylinders) - but it doesn`t start before after 10 secs. or so. Also, if I hold the gaspedal down when starting - the engine starts quicker, but with black smoke from the exhaust and smell of unburned fuel. Does all this this also indicate a leaky injector?

Since both my MB and myself are located i Thailand (where tempearturs are always over 25 Celcius), - do I really need a choke on this engine, - or can I just in any way cut it out?

I would not think that the fuel pump should run with the engine not running. The usual sequence is that the pump comes on for a second and then shuts off if the motor isn't running 300rpm or if the starter isn't engaged.

Even though you are from a warm region (I am from Florida), the temp of a cold engine is still very different from a hot one. The cars system will work well in all temperatures when performing properly. I do not know what system you have as your year is very close to some major changes. I am not even sure what engine that car has. I presume it is a 126 body 117 engine with a KE-Jet fuel system.

Read the DIY section about evaluating engine controls and find someone in your area that understands the testing, or get the tools and give it a go. (all the tests can be done with a $30 multimeter, a LED, and some wiring)

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician