MB 380SL Cold Start Valve

[Por_sha911]

3.8 V8. When first shut off, the engine fires with half a crank of the engine. If I let it sit more than 30 minutes, it turns and turns and then fires and runs rough until I blip the throttle and clear the motor (running rich?).
Sounds like classic cold start valve. Can anyone tell me where its located?

[Por_sha911]

Does no one know about the CSV on a Benz?

[daepp]

Where I'm from we called that "dieseling". I thought it was remedied by means of a positive fuel cutoff solenoid???

[Por_sha911]

Sorry, I didn't make myself clear. The problem is when trying to start the car. Typical CIS usually requires a turns for the car to fire but lately it is having to turn over many times before it will fire and then it runs rough until I clear it out with a few blips of the throttle. What tells me its the CSV is that when I shut it off and then restart after 5 minutes it fires right up.

[Por_sha911]

Last bump in the hopes that someone can help.

[fingpilot]

Joe;

Have had a number of V8 MB's over the years. My recollection is that it is a 'momentary enrichment path'. As I remember, if it is bad, it allows the stored fuel pressure after shutdown to leak past and duplicate what you are describing.

Would I trust my memory to validate a new CSV purchase in your case? Probably not. But that same Bosch system is in our 911's, and perhaps one of the guys here will be able to validate as well. Perhaps a question posted in the 911 forum (from the mid-80's FI point of view) would get a response. I see you have an '87. Don't remember if it was the II or III Bosch system.

I had a spectacular MB guy, but he retired, and I got rid of the MB's right after. If experience is anywhere close, the enrichment valve is located exactly within $400. of the injector pump.

[KNS]

Do you feel the CSV is operating even with a warm/hot start richening your mixture? Not sure I understand your question. I have found that even with a non functioning CSV, summer time first starts are usually not a problem. What is the outside air temp when you are doing that first start. I ask because it might not be your CSV.

[fingpilot]

Joe;

Just dicovered that PP has a MB tech forum. Might post there too.

[spuggy]

If it's like the CIS cold start valve circuit in the 930, it only operates

* when energized by the starter solenoid circuit
* until the thermo-time switch reaches 45 degrees

Note the TTS also has a 3w heater built into it to prevent the CSV flooding the motor; folks have observed this working for as little as a second or two, and I've seen 7 seconds quoted for -20C.

Ran my car for 12,000 miles without the TTS connected - hence no CSV - and it started as usual with ice on the windshield/ground. Hooked up the TTS, and can't detect any difference in cold-starting.

I'd be looking at the cold control pressure first, so long as the CSV doesn't dribble fuel when cranking, likely not the problem.

[Por_sha911]

Originally Posted by spuggy

If it's like the CIS cold start valve circuit in the 930, it only operate until the thermo-time switch reaches 45 degrees......
....I'd be looking at the cold control pressure first, so long as the CSV doesn't dribble fuel when cranking, likely not the problem.

I was under the impression that the CSV was activated when the motor was not up to operating temp as opposed to it being cold outside. If this is not the case then I need to move on. As far as the CSV dribbling fuel; thats why my initial question is if anyone knows where it is located. Also, how would I check the cold control pressure?

Thanks everyone for the input. If anyone has an idea where its located let me know.

[spuggy]

Originally Posted by Por_sha911

I was under the impression that the CSV was activated when the motor was not up to operating temp as opposed to it being cold outside.

On a 930, powered off the solenoid circuit when the car is cranking only - and only if the thermo-time switch is below 45 degrees.

[quote]As far as the CSV dribbling fuel; thats why my initial question is if anyone knows where it is located. Also, how would I check the cold control pressure?

With a set of CIS gauges, same ones as you would use on a 911. PP sells them, although a lot of folks prefer the $60 Sears set.

Thanks everyone for the input. If anyone has an idea where its located let me know.

Heck, I don't even know where mine is...

Here's a picture of one though, might help.



It's even the correct one for your car, from http://cgi.ebay.com/ebaymotors/Mercedes-cold-start-valve-280-380-450-560-SE-SEC-SEL-SL_W0QQcmdZViewItemQQ_trkparmsZ65Q3a12Q7c66Q3a2Q7c 39Q3a1Q7c72Q3a1205Q7c293Q3a1Q7c294Q3a50QQ_trksidZp 3286Q2ec0Q2em14QQhashZitem4cea24004eQQitemZ3303457 42414QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessori es auction.

See it's got an electrical connector AND a fuel line? You'd think it shouldn't be all that hard to find

It'll be on the inlet manifold somewhere...

[Bert38]

[QUOTE=spuggy;4793176]On a 930, powered off the solenoid circuit when the car is cranking only - and only if the thermo-time switch is below 45 degrees.

As far as the CSV dribbling fuel; thats why my initial question is if anyone knows where it is located. Also, how would I check the cold control pressure?

With a set of CIS gauges, same ones as you would use on a 911. PP sells them, although a lot of folks prefer the $60 Sears set.



Heck, I don't even know where mine is...

Here's a picture of one though, might help.



It's even the correct one for your car, from Mercedes cold start valve 280 380 450 560 SE SEC SEL SL | eBay auction.

See it's got an electrical connector AND a fuel line? You'd think it shouldn't be all that hard to find

It'll be on the inlet manifold somewhere...

Thanks for posting the eBay link. I've got the same problem on my 83 MB 380 SL. I've been searching for a CSV, but didn't want to start with a new one. Just picked up one used from the link you posted.

[Mrmerlin]

I would add a bottle of techron to the gas,
do lots of short drives so it has time to work,
your injectors may be clogged or leaking,

also add about 6 oz of MMO
this may take a few treatments to see full performance

[Bert38]

Originally Posted by Mrmerlin

I would add a bottle of techron to the gas,
do lots of short drives so it has time to work,
your injectors may be clogged or leaking,

also add about 6 oz of MMO
this may take a few treatments to see full performance

Thanks! I'll do this too. The car sat for awhile, about a year, so it wouldn't surprise me if the injectors do have some clogging/leaking. I had been trying Sea Foam. In my case other than the ocassional hard starting warm or cold, the car runs perfectly.

1983
380SL

[Bert38]

I added a can of Techron to the gas, have gone about 200 miles now with it including fair amount of starting and stopping of engine.

I picked up a used CSV off eBay which was said to be tested and all. Apparently was, works great! Thanks for the link posted in this group for the CSV. I also replaced, of course, the gasket.

What I did notice was my CSV was a bit loose ... apparently over the years the gasket had shrunk some ... I think.

So, after many starts, the starting is much better. And the Techron has not only made the engine run more smoothly, but the flickering of the gas gauge has calmed down. I think that's the Techron cleaning up (hopefully) the sensor some.

Thanks to this group I got my hard starting problem fixed!!!

1983
380SL

[speeder]

Originally Posted by Por_sha911

3.8 V8. When first shut off, the engine fires with half a crank of the engine. If I let it sit more than 30 minutes, it turns and turns and then fires and runs rough until I blip the throttle and clear the motor (running rich?).
Sounds like classic cold start valve. Can anyone tell me where its located?

No, it sounds like a classic *lack of stored fuel pressure* problem. The cold start valve would have nothing to do with these symptoms. The "cold start valve", (really an extra injector), merely squirts additional fuel into the engine when you start it cold. When it malfunctions, the engine will be difficult to start when cold. It's the choke.

Lack of stored fuel pressure is a common problem on Mercedes with CIS. It is usually caused by a bad check valve at the fuel pump or sometimes a bad accumulator, also near the fuel pump under car near tank/rear axle.

I don't have time to read all the responses here, so maybe someone already said this. And yes, the Peachparts forums are very good. Pelican bought them out last year.

[slow&rusty]

From the described symptoms you need a new Fuel Accumulator or EHA not a cold start injector.



Located adjacent to the fuel pumps.

[Bert38]

I ended up with two problems. I had a problem with the CSV, replaced it as mentioned earlier in the thread and started perfectly in cold weather. Now, warm weather is here, my 83 380SL would not start if out in really hot weather sitting after a run, like in a parking lot. I replaced the accumulator and now it starts OK all of the time ... thanks to this forum!