Starting Issues
 

I recently bought a 1992 300ce sportline in very very good condition. Obviously I did the initial 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??

Fuel accumulator
 

I find it hard to say this but it sounds like you are in the beginning throws of the accumulator going south.Seems like the last week or so this has stood out as a recurring problem.you can find several post on this subject and some good how to info as well.JNT:silly:

Check the fuel pump relay.

i agree the fuel pump accumulator sounds like the problem because the fuel pumps were replaced[along with the fuel pump check valves].

I agree with the accumulator for the hot start issue.

I think your oxygen sensor may be TU. If you can't get it below .7, then the lambda system or EHA (not sure what a '92 CE has) is going to lean the mixture as much as possible based on a false reading. So get the proper (3 wire?) generic Bosch sensor from Phil for $35 or so, then adjust your on/off ratio as described in many posts.

when u say fuel pump accumulator - is this what u are talking about ??
http://cgi.ebay.com/ebaymotors/Mercedes-fuel-accumulator-300SEL-300E-W201-W124-W126_W0QQitemZ320092563566QQcategoryZ33553QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Also where in the engine bay is it located??

yes but it's not in engine bay,it's above fuel pump[s] by right rear axle.

Hot start issue is symptom of leaking injectors flooding the engine.

Try starting with accel pedal down some to verify.

when i depress the accelerator/gas pedal down during warn start - engine catches up earlier ..
does this prove i have leaky injectors ?

It more proves you're flooded.

It also proves you're not lacking fuel, which would be the problem caused by accumulator, etc.

the accumulator being faulty causes a drop in fuel volume which is why your car feels like it's trying to start before it does and by that time the eha which blew out to about 30-40 milliamps has it too rich,hence the black smoke and rough start.

so u are saying the accumulator is fine! !! right?

David - I don't have black smoke during start- also if it was the fuel accumulator failing - then it should also have problems at cold start also - (engine temp <40 C)?

I know it is not an expensive part and can be repalced- but i just want to understand it better how things work..

So far - I have these suspects 1) OVP 2) Fuel accumulator 3) O2 sensor

pls let me know

stand behind your car when someone else starts it [during the time when hard to start] the black smoke will only last 1 or2 secs.

Starting cold without problems would suggest that.

On our previous 300E, replaced accumulator and pump check valves and made no difference in hot starting problems.

Replacing injectors fixed the problem.