clk55AMG/CL600

First post here. I have a GL that is randomly not starting especially in cold temps. I scanned it. It has good rail pressure as well as good low pressure numbers @ 69.5 psi and it is is syncing just not starting. I have no codes, no abnormal issues. Just a no start when cold as well as a random no start when warm. Upon cold cranking Rpm was 130 up to 140. So I replaced the glow plug control module, new fuel filter and AGM battery. It warmed up weather wise and the cranking speed went up to 170’s still no fire so I hit it with a tiny shot of ether and it busted right off and ran perfect as usual. Motor ran for hours then upon shut off it didn’t restart. So I plugged the scanner back in to check cranking rpm it never went above 170’s so I let it sit for about 30 minutes and came back to it and had it cranking rpm in the upper 190’s and started right up repeatedly each cranking rpm was in the upper 190’s to 205+… so question is, is the firing sequence to injectors contingent upon cranking rpm? This issue is literally running me ragged. No codes nada… everyone I speak with says change your glow plugs or injectors, fuel pumps etc…. I’m thinking stater… opinions???

kajtek1

I still would like to see a number at "rail pressure is good" ?

clk55AMG/CL600

A quick video of a successful start…. In the cold 32F or below it’s around 130-150 rpm no start after three or more cranks.
I’m on a phone so can’t see if video posted so the info is start at 192 rpm and rail pressure in the mid 1700’s or 107 bar, idle pressure is 4900 psi or 337 bar @ 700 rpm

kajtek1

I never had situation when my engine would crank for long time without firing, so could not measure cranking rail pressure, but google gives it 4000 psi.
Also injector opening pressure is listed as minimum 3200 psi.
Google takes that info from the internet, so I would take it with grain of salt, but the numbers would definitely make me searching for Mercedes WIS with precise numbers.

B34chBum

I've read on these forums the minimum cranking speed for 642 is 200 rpm.
I had difficulty starting last winter, and worked through supply voltage testing. Was starting to suspect old/weak starter.

But then I did injector leakdown test and found I had 1 bad, another leaking/black death...
I replace both injectors and car started with sub-second cranking time.
AutohausAZ had best price I could find on reman injectors, I recall price was about $150 per unit with return of cores (prepaid shipping label).

clk55AMG/CL600

Replaced the starter and all is good again! I now know my glow plugs are good, my injectors are within spec, my control module is good, crank sensor and cam sensors are working together, all starting related connections are relays are good and it's getting the fuel it needs.