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'81 280CE had rough idle...now won't start at all

3K views 12 replies 4 participants last post by  Nutz 4 Benz 
#1 ·
So here's a weird one: When it's cold, my 280CE typically can be tough to start and then runs pretty rough until it warms up, usually about 5 minutes and then it runs perfectly fine. Maybe a slight hesitation here and there, but nothing crazy.

Lately, that rough start has become no start.....for a while....then it would start and take the typical 5 minutes to warm up, then it would be fine.

Today, it would not start at all. It cranks like normal, but it sort of slow chugs while cranking, and maybe chugs for a beat or two after I stop turning the key, but it will not catch.

Here's the only other caveat to this issue: for the last year or so when I idle I'm noticing the battery light lit up, and then as I'm cruising along it goes off. I also have the worst belt squeal that I've ever had.....primarily when it's cold, and primarily when it's raining.

I'm wondering is it a valve adjustment issue? AAV (although why the no start/slow chug start)? Coil? Wires? I mean I'm really at a loss!

Anyway, I'd really appreciate any feedback that anyone has!! Thanks so much!!
 
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#6 ·
WUR is in charge of the cold and warm control pressure of the fuel injection. Upon start up, the control pressure is low and as it warms, control pressure increases.

It is located under the intake manifold towards the rear of engine. The electrical connection to WUR is shared on the fuel pump relay.
 
#9 ·
Just as a quick update: it's been unseasonably warm here in NJ for the last few days, so I went outside to see if the car would start and indeed it runs fine.

I'm leaning towards the WUR as the culprit seeing as the no-start is really related to the cold. Does that sound about right?
 
#10 · (Edited)
There's a great thread on Pelican Parts BBS in the 911 technical forum. I think the first issue brought up was problem when the weather turned cold. It all has to do with air density and air:fuel ratio. In the winter adjust the mixture to rich and lean it out in the summer. You are probably correct, the issue could be related to the cold.

If it gets cold again, adjust the mixture to rich. I think 45 degrees of turn as an initial adjustment. That's what I would do on my K-Jet 911. Worked great.

Also, and I may have missed it, have you checked the CSV (cold start valve)? My CSV quit working and the car would only start after great difficulty and even then it ran horrible. It was NLA from Porsche but I found one for a BMW with the same displacement and voltage. Plugged that in and bingo! Car ran perfect. That little extra gas made all the difference.
 
#11 ·
Thanks Nate!!! I'll have to check out that post on Pelican (I've used them religiously to keep my '83 944 running all this time)

As far as the CSV......I haven't checked it, nor do I know how to. This is really my first venture into the fuel system on this Benz. Up until now this car has been, engine-wise, absolutely trouble free. I've done basic maintenance since buying the car 2 years ago, but all my repair efforts have been focused on the exhaust (replaced from the header back) and the "rolling stock", essentially I've replaced everything that rolls (and stops) from the axles out.

The car had been horribly neglected when I bought it, but the body was straight, the interior largely intact......and it ran really strongly!

I've done the rest, had it resprayed and just now it's started in with this cold start issue. Usually I can get it running and it will warm up and run just fine, but on Saturday it refused to start.....Sunday and Monday too.....it wasn't until yesterday when it hit 55 degrees outside that I tried it and it started without hesitation.

In the past, when it would finally start (after having sat idle for 1+ week or in the cold) it would have a tremendously rough idle until reaching operating temps, then it would smooth out and if I drove it consistently throughout the day, would be fine.

Since it started yesterday, I have put it in my climate controlled garage.....figuring if I couldn't resolve this issue I'd at least be able to drive it to the repair shop on it's own 4 wheels rather than towing.

I started and drove it this morning, without issue or episode, and now I'm trying to figure what's next.

Thanks so much for your input!!
-Sean

There's a great thread on Pelican Parts BBS in the 911 technical forum. I think the first issue brought up was problem when the weather turned cold. It all has to do with air density and air:fuel ratio. In the winter adjust the mixture to rich and lean it out in the summer. You are probably correct, the issue could be related to the cold.

If it gets cold again, adjust the mixture to rich. I think 45 degrees of turn as an initial adjustment. That's what I would do on my K-Jet 911. Worked great.

Also, and I may have missed it, have you checked the CSV (cold start valve)?
 
#12 ·
Sure. I have a page from the 911 repair manual. It most likely is the same for the MBZ as Bosch made both. Do a search for the CSV or start enrichment valve. That'll give you an idea of where it is and what it looks like. Per the 911 Workshop Manual:

"1. Remove start (enrichment) valve; the fuel line remains connected.

2. Hold the start (enrichment) valve in a receptacle and connect to battery B+ and to ground with a piece of jumper wire. Briefly swicth the ignition on. The start (enrichment) valve must spray fuel in an even conical pattern.

3. Remove jumper wire and switch the ignition on. After waiting about 10 seconds, wipe nozzle of valve dry. No fuel should come out."

My guess is if you don't get a spray pattern on the jumpered test, it's not working. Or, you could have WitchHunter Performance clean and test it for you. They do all fuel injectors.
 
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