Starting issue

[martinmayer]

I've never been comfortable about the way my 1966 250SE coupe cold starts. The owner's manual says to turn the key to let the fuel pump run for a few seconds and then turn to engage the starter and don't release until the engine is running smoothly. That sounds as if it would wear out the starter motor in no time. The manual then goes on to say, if that fails, press the accellorator half-way and release, then start again. When I step on the accellorator half-way, I feel some sort of mechanism engage and when I take my foot off the accellorator, I don't have any sensation that this mechanism releases. Then when I turn the key, foot off the accellerator, the engine bursts into life, full throttle, and I've got to slam my foot on the gas to get the throttle to release and go down to a normal idle. This can't be good for the engine, to start at very high revs with no oil pressure. Anyway, am I doing something wrong or does it sound as if there is something wrong with the starting mechanisms? After the car's been running and shut down, starting again is no problem at all and does not require any use of the gas pedal.

[BenW111Coupe]

I have a 280SE, and a 230SL and the manuals for both state the same thing !

Generally I never have to use the throttle, hot or cold on the Coupe, but I do with the SL only when hot.

It sounds to me lick something is sticking or else you are missing a return spring as the car should not start up and rev away like that !

Usually when hot I would have to apply half throttle on tyhe SL and the minute it fires I remove my foot and the engine hardly races at all.

Check the linkages and the various joints but also the cross shaft which is bolted to the bulkhead may have semi sezied. maybe an accomplice could help you recreate the symptom with the engine off, since nothing changes as far as linkages go !

Good luck !

[martinmayer]

This week when I started the car I just let the fuel pump run longer, maybe a few minutes, before I tried to start. I slightly depressed the accellorator, but not enough to engage any mechanism further down. The car started immediately and idled slowly. So maybe I just didn't know what I was doing. If I could find a competent mechanic anywhere near Montgomery, Alabama, I would have the thing checked out.

[Don350SDL]

MB starters all have an overrun clutch, which prevents the engine from overdriving the starter pinion. Kind of like a ratchet wrench. So, they really do mean that you should not release the key until the engine is firing regularly. In very cold weather (like -40) I have held the key as long as 10 seconds after the first cylinder fired. (I once let it go after 4-5 seconds, the engine stopped and wouldn't restart for a few hours... I learned my lesson)

Don

[martinmayer]

I didn't know that about the starter. I'll keep in in mind and not be so stingy when starting...especially now that we're getting some cold weather in Alabama. I usually don't start any of my older cars unless it is above 50 degrees outside, but I realize that is a luxury most of the country does not have.

[wbain]

When the engine is hot, the key must be turned to the ON position for at least 5 seconds. This is because the fuel vaporizes inside the injection pump when left standing for any period of time. Fresh fuel flows through the injection pump and you can hear the tone of the fuel pump change from a high tone to a lower tone. Then start the car.

I would suggest taking all the linkages off one by one and inspecting the ball joints and sockets and the action for binding. Add a small amount of grease to each socket. When you find a part that binds, take lubricate it. There are various springs so a spare parts table would be good to look at or ask for some pics from folks of the various W111 Pagoda SL forums.

Use a good quality grease or a synthetic grease.