[BIG 500SEC]

Hi,
Got a question about starting my car. Its a 1990 500SEC. Heres the thing, when the engine is warm the car ALWAYS starts without barely turning the engine over, as i would expect, but when its cold, the engine turnes over fires once....turns over a bit more.....fires again....turns over a bit more....(does this overall for about 4-6 seconds)then starts, and runs silently, perfect idle ect. Sometimes when cold it starts like when its warm, without hardly turning over once, but more often than not it starts from cold like this! Its as though its not getting enough fuel when the cars cold (like its not being "chocked" like you did with really old cars).

Ive only had the car a few weeks, and I purchased it off the original (seriously rich) owner, its got Full main dealer history and has been mantained regardless......so Im assuming its something simple thats gone wrong- I just dont know where to start!

Any ideas? Ive heard that the cold start injector might just need cleaned??? The local Mercedes specialist was NO help, firstly saying that the car was "getting on a abit" and that they would have to charge a full hours fee ....£85 minimum just to look under the bonnet, and wont even tell me where abouts the cold start injector is without looking.....the idiot mechanic at the desk reckoned it might need a new engine management computer (which is a load of garbage!)! I guess its because Im young they dont take me seriously with a car like this!!

Any help would be greatly appreciated....
Alastair.

 

[jhodg5ck]

next time you go to start cold put the gas pedal to the floor..if this helps w/ things your injectors are shot..cleaning them won't help much (if at all) they'll need to be replaced. I'm wagering that your injectors are leaking down creating a grossly rich situation, stepping on the gas pedal will introduce significant amounts of air bringing your A/F ration back to the realm of combustible Much quicker.

Let me know how you make out.

Jonathan

 

[Jammerkiller]

Sounds to me like the cold start injector. Even though mine never "activates" since it never gets that cold here in Arizona, your problem sounds like the injector is not working properly. Try checking the fuel line to it and the injector itself. You could remove it and then test with some pressure and a small battery to open the injector valve. But, this may be a bit much for you.[8)]

Also, there is a sensor on your engine that tells the injector when it is cold enough to operate. I don't know where it is on your engine, sorry. Try mb.braingears.com to see if they have a schematic or diagram of your engine and CSI system.

 

[jhodg5ck]

My cars have started just fine w/o the cold start being enabled. The cold start valve only comes into play when it's Quite cold, ie 30-40 degrees.

Jonathan

 

[BILLSONG]

I thought 500sec where only produce from 1984-85

 

[jhodg5ck]

you could get a Euro 500SEC through 91 if I'm not mistaken.

Not terribly popular but available none the less.

Jonathan

 

[BIG 500SEC]

Hi,
Thanks for the ideas...OK, I tried starting it with my foot down this morning, didnt make any difference really...still turned over for a while before firing. Yesterday morning and again after work, I tried turning the ignition to position 2 and when the seat belt arms were almost extended I turned the key to the start position and it started first pop, no problem?

Could it be the fuel pressure isnt being held, but when you leve the key in position 2 for a second or two the fuel pump presurises the lines so there is fuel at the injectors.....dont know if this car works like this, but others Ive had did????

The night I started the thread the car was cold, and it started without any hesitation just turning the key straight to start...argh!

Yeah you could get the 500SEC in the UK anyway till late 91 (might even be very early 92...not sure) Ive seen a couple of J registration cars running about?! Like you say, not very poular....do you know the fuel over here is touching on 96p/l!!!!!!!!!!!!!!!

Alastair.

 

[jhodg5ck]

might be the accumulator bleeding down. I'd see about getting your fuel system pressures tested... W/ those numbers in hand shouldn't be all that hard to diagnose.

Jonathan