I've replaced a lot of parts to fix that car (wires, plugs, injector, coil, EHA...), it's getting really better now but I'm still having a starting issue.

If I have to re-start the car less than 15 minutes after I turned it off, it will start right away.

On all other times (cold or hot...) when I start it, after 1 or 2 seconds of cranking it looks that it's starting for like 1 second and then die. If I re-crank just after that: it starts right away!
If I initially crank it for a longer time (like 3 to 4 seconds) it starts fine also.

Fuel pump check valve have been changed without success. Any ideas?
I've eared about mass plate position adjustment?

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From 300CE to SLK230K

That car has CIS injection & runs approx 85-90psi of fuel pressure. Any fuel pressure bleed-off will cause long cranking times to re-build that fuel pressure.

The fuel pressures should be checked & then with the engine off watch the fuel pressure for bleed-off.

The most common problem is the fuel accumulator, also the fuel pressure regulator.

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Thanks for the input. I need a little bit more information here to understand correctly (forgive my ignorance on this).

I thought about fuel pressure bleed-off and did the following test: I turned ignition ON and OFF many times before cranking, which ignite the fuel pump for about 1 second each time, thinking that it will rebuild any pressure loss in the fuel line. Am I right or missing something here?
When doing so, it doesn't change anything to my starting issue, that's why I thought... please help me to understand this probably bad troubleshoot.

Other questions: how would I check for pressure drop? Hooking a pressure gauge to the fuel line? On the distributor? somewhere else?
How can I distinguish between pressure regulator and fuel accumulator, which one is the faulty?

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From 300CE to SLK230K

So I replaced my fuel pressure actuator which was leaking: fuel bleeding through the return line when off, so I thought that's how I was bleeding gas, causing the car to require a long crank to evacuate air in the system.
The new one is not leaking but... it didn't solve my problem!!! Still the same issue.

I'm getting frustrated here.

What can cause that? Bleeding cold start injector?

Any ideas guys?

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From 300CE to SLK230K

wut about your pump ? is it noisy ? have u checked the pressure ?

The pump doesn't seem noisy (to me).

I was not able to measure the pressure yet, because the fuel pressure gauge set I've got is working for GM, Ford... no Bosch fitting.

I was trying to build an adapter by buying and extra set of screw + joint which close the top of the fuel distributor (to thread it and have my gauge adapted to it) but MB doesn't detail that screw...

What kind of fitting is required to monitor fuel pressure?

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From 300CE to SLK230K

Something new to my problem here.

We've got a cooler winter here in Southern CA and it's been few mornings when I have to start the car at temp around 40 to 45F : the car is starting without issue.

Basically I get this problem if the temperature is over 55F on the morning or if it's been seating for more than 30 minutes...

I was not able to check fuel pressure yet (didn't receive any suggestion on my previous post).

I understand that the cold start valve must start injecting some fuel at those temps, helping to start the engine, but I was just wondering if it could really mask by problem if it was related to bleeding like I've been told?

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From 300CE to SLK230K