My 89 300SE starts immediately everytime and runs smmothly when it's 50 degrees or lower. When the engine is warm on a day above 50, it cranks a long time and when it does start it idles roughly for 5 to 10 seconds, then smooths out and runs fine. My mechanic says that this car has an older(less sophisticated)F.I. system and the hard start with a warm engine is characteristic of this vintage Mercedes. What do you think?

What happens on a hot start if you depress gas pedal a bit durning cranking? Sounds like fuel bleed off from injectors, f/dist, & or fuel accumulator.

I think your mechanic may not understand how it works and is afraid to tell you . It is not normal.

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by M.B.DOC:
What happens on a hot start if you depress gas pedal a bit durning cranking? Sounds like fuel bleed off from injectors, f/dist, & or fuel accumulator.<HR></BLOCKQUOTE>
M.B.Doc,
Depressing the gas pedal makes the engine crank longer without starting. Why does the engine start so fast when cold vs. hot?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Benzmac:
I think your mechanic may not understand how it works and is afraid to tell you . It is not normal.

<HR></BLOCKQUOTE>
Benzmac,
My mechanic may not understand how it works.
I would like your opinion on why you think the engine starts better cold vs. hot and what will fix it. Thanks.

These may be utterly irrelevant to you, but having recently changed my '89 500SE from a spluttering high idle to a 600rpm purring kitten, I can suggest:

• Check the HT cables and system. Put a meter on each ignition cable and check for 1kOhm continuity on each. Clean and if possible tape up any junctions. Examine the running engine in the dark and look for brush discharges and other signs that the high voltage is escaping.
• Clean the distributor cap and look for unusual signs of tracking around the internal contacts.
• Check the connection to the Rotary Idle Valve. The contacts on the connector may be corroded; clean them if so.
• Check the idle jet operation. I found that unbolting it from the engine allows it to be withdrawn far enough to see the nozzle. Using a piece of wire to the battery, you can fire the solenoid, and if it's working a fine fuel spray will squirt from the end.
• Check the idle switch. On mine it's deep in the bowels, attached to the throttle butterfly, but the connection cable is easily accessible. With a continuity meter you should get a contact closure between two of the pins at fully closed, and another at fully open. Verify this.

In my case the idle switch was defective, and one spark-plug cap was open-circuit. Correcting these two, and generally refurbishing everything else in the system, turned this wheezer into a purrer.

Best,

CD

Could be your coolant temp sensor that sends engine temp signal to ECU and ICU. If this signal is not correct, the air/fuel ratio is messed up. Maybe the ICU thinks your car is still cold and sends in more fuel than needed. I dont know where it may be located on your car, but you can ask people on FastLane or whoever your parts dealer is, try replacing it if you have not replaced it ever. For reference, on my 87, 260E, it is the last sensor on the engine, closest to the windshield, because there are more than one coollant temp sensor on my car and perhaps on your car too.

Intersting...as my car started out running real hot
after radiator change its acceptable

Would this be applicable to a 83 SEC?

I'm having the same hot start problem
starts in a nano second when stone cold

but oooh it struggles when the engine is at or even below operating temp.
Depressing the gas petal a bit does not really cure it
Still have the problems
but it does eventually start
but I am draining battery & starter motor

Its a one run car
After that it wants to rest...LOL

Ole timer....

Thanks

Do you have a red TVV
that opens at 50C

I am assuming you are talking about external weather temp not car?

Odd but maybe it has something to do with that TVV?

Camelotshadow, did you get your problem resolved? Sounds like our's are EXACTLY the same.....

cdplayer
 

Take M.B. Doc's advice. I replaced everything from the fuel pump. accumulator, filter, vapor valves forward to the injector seals and seats. Dist. cap, rotor, and breather hoses that run under the fuel distributor.
Still had warm/hot start cranking issues.

Finally, I bit the bullet and bought a new set of injectors along with new seals. My '84 500SEC starts instantly warm/hot/cold. Ten seconds after shut off or two hours. I have 237,000 on the clock with origonal pistons and rings. And she starts right up each and every time.

The cost of new injectors, seals, and seats is worth cancelling the frustration if you can do it.

Search my other posts (cdplayer) if your SEC has issues. Perhaps the struggle I have endured will help you out some.

Have a great day!!!;)