StarGazer

I recently bought a 1992 300ce sportline in very very good condition. Obviously I did the inital pre-buy check etc and everything looked fine... also the guy had receipts of all repairs since 1993 when he bought it.

Suddenly the car has developed some trouble with regard to starting.
1) when engine is cold (engine temp <40 C) - one crack for like 1~2 second the car just starts up..- idles 800~1000 for some time and the idle drops (i presume this is normal)

but car seems a little resistive as if lacking fuel when you drive out - especially if push the gas a little more - it kind of catches on and is ready to fly!

2) when engine hot (engine temp 85~90 C) the car will start up in one crank - no problem here

3) PROBLEM - now leave the car for 10 mins or so and come back and crack up it takes like 15 sec of cracking and gas pedal pumping/pushing to start - also it starts rough and then evens out at normal idling...and drives fine after that.

I took it to an independent mechanic (C& H auto, Chicago) - where we changed Sparkplugs to Bosch Platinums - no improvement. {receipts say flue filter was changed like 3 yrs back with fuel pumps}


Also a voltage check across oxygen sensor was at 0.7 -0.8 - idly i guess it should be around 0.5 - but playing around with the fuel air mixture is very very sensitive and we could not get it at 0.5.

So next it seems as the oxygen sensor - but I am not sure if I am on the right path.. The independent mechanic comes highly recommended but he is also trying to figure it out. He suggests - distributor and wire replacement (tune-up) and fuel system cleaning.

I know a tune is something I need to get done since the car was owned by an older gentlemen and sat for 3 months -so far have changed oil/oil filter and topped off all fluids. (transmission and radiator flush need to be done).

Anyone has an ideas or know what could be the issue??

NorCal124

Its your OVP relay, ha i win again!

StarGazer

Are u sure it is the OVP relay?

DarkHand

Wait till others weigh in on the details...chuckle

I smell a herring being swung around here...or is that a dirty sock?

shdoug

'92 CE? That's the 3.2 liter but...it's K-Jet, not HFM so I'm thinking not the OVP. Am I right? It sounds like a fuel pressure leakdown or vapor lock problem to me. Even if I'm wrong about the engine you have, the O2 sensor has no function at startup; the sensor must have exhaust flowing and be at full operating temp before it comes into play.

If you do have HFM injection, follow this link:

https://mbworld.org/forums/e-class-w124/25505-95-e320-intermittent-starting-problem.html

NorCal124

It won't hurt to check the 10 amp fuse inside the OVP relay, the pumping of the gas, rough idling, and long cranking are symptoms of a bad relay (or fuse inside it). You're not helping the problem either, W124s were designed to use standard copper bosch plugs. Platinum plugs will feel great at the beginning but will begin to cause very rough idle. In worse case scenarios Platinum +4 plugs have been known to break off tips, not a pretty sight.

jpganman

I have the same exact problem with my 400E. Is it more likely the OVP w/ the 8 Cyl engine

shdoug

Did you check out that link I posted?

jpganman

checking now, thanks

jpganman

shdoug,

read the posts, thanks for the help. I went to mercedesshop.com to buy the part, they didn't list one. do you have to go to the stealership to buy this?

shdoug

I didn't see it either. You might try E-bay.

bjay51d

I was chasing a hard start cold/hot on my car also.I also was getting pretty ****ty gas milage and poor acceleration.some times the car wouldnt even start at all if the temp 85c or more.I ended up tweaking the E
HA valve today and the results are good so far.My car starts with out pressing the gas, and it moves out now, much better acceleration.I'm not getting my hopes up though.Everytime i think I found the golden goose it turns out to be a dodo bird...

fredvillanueva

yeah I put off a neutral safety switch repair for too long by starting the car in neutral ... good interim solution, til it left my wife stranded : ( . I believe that by starting in neutral too much I killed the OVP (also a repair postponed) which finally killed the car on the road. I also replace the fuel pump relay. Goes to show you that one thing leads to another.... a snowball turns into an avalanche. Any replaced all and she's back n the road. A word of warning to the wise. How I got the car to start again: plugged in an OVP from a junkyard and it fired right up. It was also bad, but helped me identify the problem..I ordered from autohausaz.com .