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marketstar 01-24-2015 05:02 PM

cold start hesitation & rough idle 560sel
91 560SEL - cold start takes awhile to fire up, once running into the store 2 mins later - fires up immediately .. e.g when warm, car starts right up with no hesitation . . when cold, takes about 10 secs before it starts - battery is AOK.

I also have another issue which may, may not be related. The car has now starting idling ROUGH when in park. It runs like a beast when I have it on the go but it's starting cold slow and idling ROUGH when at a traffic stop.

I am new here so look forward to whatever insight and guidance you can provide . . thanks

Elektri 01-25-2015 11:11 AM

I would start with the factory service manual fuel pressure test. One of those tests is pressure. Another test is to turn the car off and see if the fuel pressure holds for a specified period of time.

Harbor freight sells a fuel pressure test kit which includes adaptors for KE-Jetronic fuel pressure testing (and seems like EVERY other fuel system ever made - I think there may be an adapter for the Space Shuttle in there too!)

An "internal leak" in the fuel system could be the trouble with the cold start issue.

bsmuwk 01-27-2015 01:07 PM

Read over this:
What to do when my M103 is giving me trouble: A beginners guide | Artisan

I realize it's M103 related, but it's not M103 specific. A lot of the M103 components are in similar use on your M117. You don't have to do any parts replacing just yet, but do yourself the favor and systematically go over your car (if you're capable). Basic tune up parts can be cleaned for testing, so on and so forth.

From previous experience, simple is usually the best way to go.
When was the last time the fuel filter was changed?

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