car starts fine runs smooth until reaches norm temp. then a blip of the throttle causes it to cut out ,after that it wont start . changed coil .changed plugs ,ascertained steady spark at plugs ,with a timing light. been suggested may be B11/2 sensor. can anyone suggest test procedure for this i have a good multimeter.also could do with idea on location of diagnostic connector. is this obd2 as i have some diagnostic equipment. is thislikely to show up on a diagnostic check. any help greatly appreciated . fault finding steps etc
thnaksfor looking

* Generally need more information.
* 300sl 24v???? Are you talking about an SL320, '94-'96 R129.063 with HFM 104 engine? Or maybe a '97 SL320, R129.063, with ME 2.1, 104 engine?
* Codes? Ideally, do a short test and write down all codes. Reset (delete) all codes and use car (if possible) through several drive cycles. Then rerun the scan for codes. Those are the codes to pay the most attention to.
* Fuel pressure? Measure it with cold engine. Leave pressure gauge on engine, out of the way, while engine warms up. Watch pressure again when engine is hot, particularly when engine cranks and won't start (right).

__________________
ASE Master Tech
Quality Enterprises
Mercedes Svc. & Restoration
Sheridan, IN
317.769.3536

hi its a 300 sl 1992 model with m104 engine , cant really do anything about codes as i cant find obd2 connection can anyone tell me where diag connector is on this model. i have various connectors with gear ibought a while back,may have to hunt out software for it though, thanks again

* '92 300SL (R129.061) with M104.981 doesn't have an OBD plug. The data plug, I think the rectangular 16-pin rather than the round 38-pin, will be over by the right hood hinge.

__________________
ASE Master Tech
Quality Enterprises
Mercedes Svc. & Restoration
Sheridan, IN
317.769.3536

hi first of all thanks for your time in this, as you probably realise im not exactly an expert on the new breed of electronic orientated cars ,although i have been an pro mechanic off and on for years .think i would be scared to death of working in a garage these days though!
i have found the 16 pin connector ,i also have elm and tachopro interfaces .can i use these to talk thru this 16 pin connector?
dont seem to have a plug that will fit ,but wondering if i can wire it up with the help of a diagram / pin map .
i have a soldering iron etc.
also ive been hearing about a method of counting flashes from a test lamp ,conecting up to this 16 pin connector/
hope im not confusong you too much
thanks again steve

* There are several posts about people taking their Benz to Autozone for a (free?) fault code scan. I've never tried this myself (since I own the test equipment) but it might be worth a try. Since your car only starts and runs until it's at operating temp, getting to an AZ might be a problem. If you've got one closeby, call ahead to make sure your AZ branch can handle the scan (and since a scan is done with the ignition on and the engine off, you may need to plan on a wait while the engine cools down).
* You could probably install a resistor across the coolant temp sensor plug and trick the control unit into thinking that the engine is at a constant 20degC. There used to be a little test harness for the M103 engine that did just that. Incidentally, I replace coolant temp sensors just for good preventive maintenance. They're cheap, easy to install, and get rid of an assortment of irritating, mysterious foibles.
* There are also posts on this forum explaining how to make a rudimentary scan tool. That's likely more of a hassle than it seems, complete with "surprises" and complications, but it's a possibility. Sorry I don't have a reference for you, but a DIY search (homemade scan tool) or a PM to a moderator should get you some references.
* You'll probably want to do the scan in two parts. Read/record the fault codes. Reset (delete) the fault codes. Use the car thru several drive cycles. Be sure to try the unsuccessful hot restart in your driveway. Then scan for fault codes again. Some of the old codes might be gone and there might be new ones.
* You're probably aware that there are fault codes that give you a failed component, and then there are many more fault codes that just tell you a condition (like a cylinder misfire) which you probably already know.

__________________
ASE Master Tech
Quality Enterprises
Mercedes Svc. & Restoration
Sheridan, IN
317.769.3536

hi thanks for all the help and support ,just to let everyone know it was the temp sensor ,bit the bullet and spent a few dollars , running great again . thanks guys