I did some searching,and before I replace the fuel pressure reg,I thought I would ask...the symptoms seem odd.

85'500sel us,takes about 3-4 seconds of cranking to start...Just started doing this after a long trip so did not happen gradually.I have good vacuum at idle and have fixed about 10 leaks..It is getting colder here,about 40 in the morning.Also runs perfect once started,no funny idle,no hesitation,no sputtering-which kinda rules out fuel filter/ignition for me.

Now the odd part...once started,you can shut it off and it will start repeatedly almost instantly..The longer you wait to start,the longer it takes.This leads me to believe maybe fuel is leaking down from the regulator/injectors.But that shouldn't make it hard to start in the mornings,Right?

It cranks normal speed,and runs like a top otherwise..Any direction on where to start would be helpful.I have already changed out the fuel accumulator/fuel filter/plugs/wires/cap/rotor...

The rear fuel pressure regulator does leak down pressure..But I doubt it would cause this problem.
\Thanks guys...

Fuel pump check valve?

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

Ordered the check valve...hope thats it.

You would probably want to do the accumulator as well.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

already done it....2 days old.

Missed that one, sorry.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Ok,changed out the check valve and the fuel pump relay...but still slow to start.

Will start better if I pump the pedal,like it has a carb...takes a few seconds to smooth out the idle,but then runs fine.Anything?

At 40 degrees, you should get shot of fuel from the cold start valve that would cause the engine to fire. So I would check out the valve and the relay that energizes it, next.

Lots of posts on both.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

it was 60 degrees today,and it is the same.

To go back to your original description and question, you are obviously losing pressure slowly. The longer the car sits, the more pressure it loses. Now that I think about it, if there's not enough fuel pressure, then the cold start valve won't do much good.

AllDataDIY suggests reconditioning the pressure regulator in the fuel distributor with new o-rings if there is a pressure drop below 2.5 bar after 30 minutes of sitting.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Hi there,
I am sorry to say that mine does pretty much the same. When I come back from a trip and start it after it stood for 3 weeks, it starts within 1/2 second. But the next morning it will take it's time. Within 15 minutes of parking, it will start immediately, but anything longer and I need to crank with or without pressing the accelerator.
My theory is also leaking injectors. With time, the leaked fuel evaporates and it will start easy.
One of these days I'll replace them all.
If somebody replaced the injectors, maybe he can chime in.
Good luck

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Reinhard Kreutzer
1987 420 SEL (126)