Dimitri,
In reading your well answered responses to my questions, I'm now perplexed as to why/how the problem focused on a fuel delivery issue? Though that's still one of the possible reasons the idling symptoms don't sound like a fuel delivery source to me.
In particular ---
- car ran just fine all warmed up and everything, with no idle problems, then just dies while driving down the road.
- thereafter idle is poor and difficult to maintain at all, and then only by careful throttle... too much or too little it dies.
- fuel in the final filter container would let car idle from start without issue even if fuel delivery from tank were extremely poor... so not a fuel problem in delivery from tank to pump.
- you get smoke after maintaining a poor idle for 15 sec's or up to a couple of minutes ... with backfiring too boot.
quote:
It never has good idle. After 15 secs and a little more throttle, the idle will smooth out a bit but the car will put out a profuse amount of white/gray smoke and then backfire a few times.
My first inclination is to think these symptoms sound like a valve timing problem.
The backfire occurs with an ignition during or near the start of the exhaust stroke (intake, compression, ignition, exhaust). This indicates the spark (ignition) occurs too late (too retarded) or way too far advanced relative to valve timing (ignition occurring too early in compression stroke so intake valve isn't completely closed... so not technically a back-fire from the exhaust but backfire into the intake manifold)... or put another way, spark's too retarded, or exhaust valves opening too soon or aren't closing far enough.
Have you checked compression? ... which would indicate a valve timing or seating, or valve guide leakage problem if it exists --- though you wouldn't be able to distinguish from warn compression rings.... the symptoms would allow you to focus on the valves.
What's the state of your timing chain? How many original miles on the cam sprocket and timing chain?
Was the cam replaced when the head was overheated, warped and replaced?
My thinking runs like this --- it starts but idles with difficulty .. probably (my guess) having to add a little bit of throttle to maintain an idle as time goes on. The white/grey smoke at the end, before it finally stalls out sounds like incomplete combustion ...i.e. ignition occurring too late in compression cycle or after exhaust valves open (or if poorly seating). This symptom is consistent in reason with the backfire symptom. The reason this doesn't occur immediately on starting probably (just my guess) has to do with combustion chamber and valves heating up while trying to maintain an idle.
I see no reason why a fuel delivery problem to the engine would
1) cause a poor idling condition in the 1st place (unless some cylinder's were getting fuel and others not), &
2) create grey/white smoke as fuel depleted, &
3) force a final back-fire or two before engine died.
Furthermore, you've now checked the CSV's function and find no issues, so sounds like it's either fuel timing (injection timing) or valve timing. .. .and fuel timing should be constant and wouldn't suddenly change to cause back-firing.
So my curiosity is aroused as to how and why a fuel delivery issue is or has been the primary diagnosis thus far?
An expert on these symptoms and causes with the W113's should chime in at this point.
I'm not an expert on this by any stretch though --- I've worked on VW & Porsche engines years ago (rebuilt them from scratch), my truck's former 283 & now 327, but not on the W113's. My primary experience with valve timing comes from playing around with my 327's valve timing and ignition timing combinations.... advancing (mostly) or retarding things (by error) to maximize acceleration and power at the expense of fuel efficiency. It was during those experiments that I frustrated with poor idling, grey/white smoke, etc.... and I was working with my 327 with unknown but umpty-ump gazillion hard miles on it, and my old high compression heads before I decided I had to have the entire mess rebuilt from the ground up. I'm also not a gear-head.... I worked on the VW engines for want of money to pay anybody else to fix the one I nearly melted.. initially for economic necessity as I'd never, ever done anything more with an engine that put oil and water in them. I worked on Porsche engines for a couple of friends (356's) because they're no different from VW engines in principle, and it was just fun in my spare time (this was after I'd attained a level of economic freedom). I worked on the 283 and 327 engines in my truck because I wanted to learn more about water cooled big ("real") engines and systems... and again it was for fun and learning (by which time I could easily afford to have somebody else do the work... which I eventually had them do... built from scratch to my spec's).
I've timed my W113 myself a couple of times, and will do so more often now that I retired, but getting the engine to tdc (or where-ever I was supposed to get it) is a **** compared to VW's and GM engines.... and neither of those have to deal at all with fuel delivery timing.... just the mixture. I'll offer that my distributor is the car's original Bosch and that the rotor shaft cylinder bore is slightly warn, hence I have to offset my static timing slightly to get the dynamic timing right... the bore wear causes a bias in point set point compared to after driving the car around the block. The offset's not enough to hardly matter and I can't really notice the difference except under a hard accelerations.... certainly not at idle.
Longtooth
67 250SL US #113-043-10-002163
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