SL/R129 SL320 Hot Start Issue - MBWorld.org Forums

Jul 31, 2019 | 07:42 PM

Midnightsun

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Junior Member

Joined: May 2009

Posts: 25

Likes: 3

From: Montreal, Canada

2017 GLC43 AMG

SL320 Hot Start Issue

I seemed to have developed an issue when I start the car when the engine is warmed up or has been in the hot sun for several hours. Seems like the cold start injector is getting a signal to activate as the engine starts then quits. I once again turn the key and it turns over several times before it starts rather roughly with a small cloud of black smoke from the exhaust. Once it runs smoothly which is only a few seconds later it runs like a top. Cold start there is no issue whatsoever. Plugs, wiring, filters and even the MAF sensor are new. Car is mint with only 38,000 miles. Engine is the in-line 6 which I believe is the M104.

Got any ideas on what to check out. Air intake temperature sensor?

EDIT: Ordered the intake temp sensor for the heck of it, just makes sense this may be the issue. Will post back once received and installed.

Last edited by Midnightsun; Jul 31, 2019 at 08:09 PM.

Aug 1, 2019 | 08:40 AM

bobterry99

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Joined: Jan 2006

Posts: 1,982

Likes: 393

From: Atlanta, unfortunately

'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55

The engine controller looks at the coolant temperature sensor -- not the air temperature -- to determine whether to enrich the mixture for cold start. Cancel the order if you can, or return it in its unopened box once it arrives.

You can test both sensors very quickly and easily by measuring resistance across their electrical terminals and referring to charts. All the information is in the diagnostic manual: http://manual.startekinfo.com/manual..._1/content.jsp

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SL/R129: SL320 Hot Start Issue

SL/R129: SL320 Hot Start Issue