R107 Turns but won't start

[MYMB350SL]

Hello,
My R107 350SL (1977) has always started on the second turn of the ignition key virtually every time over the last 2 years .

Recently, when I drive it for an hour and leave it sitting for 2/3 hours it turns but refuses to start. Consistently! but still starting from cold (after the second turn of the key).

I have found myself having to jump start almost everyt time I go out for a length of time and it starts immediately. So thought it's definitely an electrical problem and changed the brushes on the alternator with a new battery in. It's turning a lot more healthily but still won't start if I try to drive off after a couple of hours somewhere... pain in the neck as I'm always wondering if I'll ever get home... or do I need to leave it to sit there till the morning...

Electrical? injectors? f. pump? who knows... any help would be appreciated.

Thanks
H.

 

[alabbasi]

Sounds like vapor lock to me and that you're constantly cranking to get new cold fuel back up to the fuel rail.

 

[219]

Fuel accumulator ?

 

[alabbasi]

Fuel accumulator ?

Yes, very likely. For some deranged reason, I read the year as 1972 when I first looked at the post. As 1977 makes it a CIS car, I would look at the fuel accumulator as the first thing to replace.

 

[MYMB350SL]

Thank you both. Will go ahead and replace it.

Any good places to look for replacement instructions?

 

[219]

It is worth watching this video showing the process on a W126 , essentially the same job .

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Also , you can go to your local library and borrow , or go online and buy , the Haynes manual for the W123 series which in many aspects is mechanically similar to the R107 , and for this item will be just the same .

 

[219]

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102 103 104 Gas Engine Difficult or Slow to Start | Fuel Delivery Problem | MercedesSource.com

mercedessource Tech help - Begin with the "back end" fuel delivery system first. For many owners of 1984 to 1995 102 (4 cyl gas) 103 (6 cyl gas singe cam) and 104 engined Mercedes (6 cyl gas twin cam), clean starts are becoming a fading memory. By “clean start” I mean the engine starts quickly...

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[MYMB350SL]

Thank you folks. The accumulator did the job but only lasted less than a week and now back to having to pump the pedal a few times to help it start... changed the plugs and old ones only showed slight fuel leakage from a couple of injectors otherwise look ok and also changed ignition cable set. Apart from taking out all injectors and cleaning/replacing them, not sure what else to try. Not sure if the current heat wave has anything to do with it either...