*sigh* stalling *sigh*

[RickInTex]

I'm hoping there's a quick, inexpensive fix for this that will keep me from having to go to the mechanic, but the more I search the forum, the less sure I am.  

So:  coming home today, having driven the car off and on for a couple hours, I began to experience problems with stalling as I came to a stop or even when shifting between gears.  By the time I got home, the only way to keep it from stalling was to hold the engine around 1500 with the accelerator.  It would start instantly but stall immediately unless I depressed the gas.  I also felt like there was marginally less power when underway and maybe a little rougher/louder than normal--but I could be imagining this.  In between stalling and restarting I could smell a strong fuel odor from inside the car--I wasn't imagining that.

Context:
4-spd. 67 250 (orig. 230, but previous owner rebuilt with 250 head), which I've had for about 4000 miles, since last May.  Previous owner had injection pump rebuilt as well--perhaps 2000 miles before I bought it, but 7 years earlier.  Because it was driven so little in the years since the rebuild, it smoked a lot when I bought it.  So I had the valves redone about 3000 miles ago, which cured the smoke.  At that time, the ignition wires were replaced, as well as standard tune-up items, filters, oil in inj. pump, etc.  Also, had linkage and other items cad-plated, lubed, etc.


Maybe relevant, maybe not:
I drive the car not quite daily.  Since the valve job, it's run beautifully, with the following exceptions.  I've always had intermittent idle issues, since before the valve job.  Starts and idles fine from cold--a little high, then settles down to about 800 after a minute or so, which I gather (maybe wrongly) is what the CSV should do.  After driving maybe five minutes, the idle will start fluctuating up and down a few hundred rpms--perhaps because I've got the idle adjustment on the air intake too low (I've never fiddled with any other adjustment).  But that's been my way of dealing with the following, which may or may not be related to the stalling issue:  when fully warmed up, the idle is stable, but it can settle at anywhere from 800 to 1400.  I've felt certain about any pattern to this at all, except that longer drives at higher rpms seem to be followed by a higher idle speed.  Still, this has not been troublesome.  A final, perhaps irrelevant detail: under hard acceleration, I sometimes smell fuel faintly.

So, as to the stalling:  any thoughts about what to check first?  CSV?  Injection pump/linkage?  I'm assuming--perhaps wrongly--that this is a fuel, not electrical problem.  I'm hoping this isn't the first evidence of an injection pump about to check out on me.  I don't have the time or expertise to do a whole lot on this myself, but even if I can't sort things out on my own, I'd like to have a sense of what the nasty possibilities are before taking it to my mechanic.

My pagoda is my therapy these days, and this has me bummed.







Rick
Dallas TX
1967 250SL, 4-speed

[rwmastel]

Rick,
If you want to start troubleshooting with fuel, do a flow rate test where the line returns to the fuel tank.  Do a search, but I believe the electric fuel pump should disperse 1 liter in 30 seconds?  A fuel pressure test would also be in order, but I don't recall how to do that.  Your suggestion of testing the CSV on the intake manifold for leakage is good, it's a simple test.

If you have a document or manual that states all the proper fuel injection linkage lengths, you could check to see if they are in spec.  If not, other FI Pump adjustments were probably made to compensate and this makes troubleshooting the fuel system difficult.  I mention this because the WRD (warm running device), shims under the FI Pump thermostat, richness adjustment, and so on could be off if the linkages are not right.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[Cees Klumper]

Maybe we can separate the longer-standing idle etc issue from this new problem. I would do what Rodd suggests first: check fuel flow and pressure, because it sounds like fuel starvation to me. Could be a leaky line or hose somewhere, the electrical fuel pump becoming defective, contamination in the tank or (return) lines, fuel filters etc.
There is lots of information here on this fairly straightforward system. You should be able to do at least this diagnostic work yourself. You can also check the technical articles where there is quite a bit on the fuel delivery system.
Good luck, and I'm sure others will chime in and keep us posted!

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[Ben]

I would firstly ensure that the ignition timing and dwell are spot on. there is no point trying to set up a smooth idle if that first basic step is wrong.

Also whilst looking at the distributor you should ensure that you dont have a broken spring or stuck weight. This can cause irregular idle speed, if the weights are stuck then at high rpms they will fly out centrifugally but they wont return when you slow down.

Also a broken spring can cause all sorts of irregularities with the idle and you'll need a timing/dwell light to check. You can physically check if you look into the top of the dizzie you can just see the spring tags at either side.

Anyway I would start here and definitely check that CSV for leakage !

Regards,
Ben in Ireland.
'64 230SL 4sp.

[RickInTex]

Thanks for the suggestions, and I appreciate you guys weighing in.  I hope I'll have time this weekend to start checking things.  Assuming they're unrelated, if I can take care of the stalling problem, the idle issue can wait.  We'll see.

Rick
Dallas TX
1967 250SL, 4-speed

[ted280sl]

Rick,
  Checking the CSV is the easiest test. I believe it has been discussed many times on this site but, it merely requires you to remove an easily accesible bolt and turn the ignition to the on position to see if the valve is closing. The points can be tested a number of ways but, if you have not changed them recently, change them.
Good luck,
Ted 1969 280Sl Traveling to Dallas 3/12

[ja17]

Hello Rick,
It sounds like you have one or more spark plugs fouled. Start with the cheap easy stuff first. Read your spark plugs they will give you the first clue.

Replace them if they are suspect even if the ones in the car are fairly new. Try to get the correct non-resistor type. Test the plug wires and ends with an ohmmeter.

Once the car is hitting on all six again, go onto system checks as suggested by the others.

Keep us up to date we can be more specific  with the diagnosis when more information is available. Good Luck!

Joe Alexander
Blacklick, Ohio

[Klaus]

Maybe relevant/maybe not:
It's an earlier car and should not have that, but when they reconditioned the engine and injection system, did they equip it with deceleration shutoff?
(a switch in the system could be stuck)

Klaus
1969 280 SL

[hands_aus]

one litre in 15 seconds

definitely replace your points

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[George Davis]

Rick,

my car had a fluctuating idle problem for a while, too.  In general, idle speed, idle air/fuel mix and idle igntion timing are all very intimately related.  In my car's case, with 3 degrees ATDC idle timing, the idle mixture adjustment became "insensitive".  By that I mean that when the idle air/fuel mixture gets too rich (too little air) or too lean (too much air), it is supposed to slow down; fastest idle is at the correct air/fuel ration.  In my car's case, I could keep opening the idle air valve and the engine just ran faster and faster instead of slowing down as it got too lean.  Before I figured out what was going on, I'd set the idle speed around 800-850, but the mixture was off and after a drive the idle speed fluctated all over, from 600 to 1000 rpm, and it occassionally stalled.  Since you have played with the idle air (but not the idle fuel) adjustment, I'm thinking the idle mixture may be set way lean resulting in the same kind of "hunting" and stalling that my engine did.  The solution for me was to back off the idle ignition timing to 2 degrees ATDC, and at that point it began behaving properly and I could adjust it correctly.  This was done by adjusting the control rod on the distributor's vacuum advance mechanism.

So after all that blather, start by doing a good tune up and making sure your timing is on spec at all points, and then adjusting the idle air/fuel mixture to the correct mixture.  If it settles down and idles right, great; if not, consider backing down the idle timing a degree or two and try the idle adjustment again.

George Davis
'69 280 SL Euro manual

[A Dalton]

<<By that I mean that when the idle air/fuel mixture gets too rich (too little air) or too lean (too much air), it is supposed to slow down; fastest idle is at the correct air/fuel ratio. In my car's case, I could keep opening the idle air valve and the engine just ran faster and faster instead of slowing down as it got too lean.>>
 GD,
 If one opens  the air bleed valve [attemptimg to lean a/f mix] and the RPMs continue to increase past spec., the problem is the pump adjuster is set too rich. By leaning the bleed , you are adding more air to the mix, but because the pump is rich, the RPMs just increase as you attempt to get proper a/f mix.  If the fuel  metering adjuster is correctly set at the pump , the air bleed should collapse on both too rich and too lean settings [ both directions, in/out- as you stated].
 . When the 1/2 way point [best RPM, or better yet, best vacuum] is found between the lean/rich settings of the bleeder air valve, one then looks for the correct idle RPMs. If the Rs are too high, the pump is rich, if the Rs are low , the pump is lean.
 I alway set the pump just a hair rich so that I can bring the idle down a 100 RPM from its highest setting with the bleeder, as highest rpm w/no load is slightly lean.
 An easy DIYer test -- If one can not get the engine to drop RPMs with air bleeder either turned both in AND out too far, then the pump adjuster is not correctly set.
 [ assuming ALL others specs are met , ie-timing , links, etc]

[RickInTex]

Update:
This weekend I checked timing, plugs, points--all looked good.  The Cold Start Valve seems to be operating properly as well.  I kind of reached the limits of what I can do and took it in this morning to my mechanic.  He's confirmed that ignition seems to be fine and timing correct, but it runs way too rich.  He's tried adjusting the mixture and says he's done this as far as it can go, and it's still too rich.  He's going to try completely disconnecting CSV and see what that does, but if that doesn't change things, he's thinking that the injection pump needs to be rebuilt.  Big bucks for that, of course.  
So, what am I forgetting or overlooking that might cure it without going down the injection pump rebuild road?  Any thoughts?


Rick
Dallas TX
1967 250SL, 4-speed

[George Davis]

Arthur,

I agree it should do you described.  On my injection pump (rebuilt, so I'm not anxious to have it rebuilt again), with the idle adjustment set to give about 650-700 rpm, the too rich/too lean behavior was correct, that is, it slowed down as it got too rich or too lean with the air adjuster.  But just one more click on the inj. pump to try to raise idle speed and the rpms just kept climbing as I opened the air valve, to 2000 rpm or more.  Very baffling behavior.  This might not be a problem if a CO meter is used to set the idle mixture, but it really makes life difficult if you're using the tach&vacuum gauge method.  After trying to puzzle out what might be wrong, a friend and I concluded that the inj. pump was running out of idle adjustment and the flyweights were taking over.  Don't ask me to explain our theory, it's the kind of crackpot thing one comes up with when one doesn't really understand what's going on.

At any rate, we also guessed that backing off the timing would help, and incredibly enough, it did.  Retarding 1 degree at idle made it possible to set the idle speed and mixture in the 750-850 rpm range.  If the car behaves as above and everything else is ok, it's something to try.

George Davis
'69 280 SL Euro manual

[A Dalton]

G,
 I see..
 One would not expect that big of a change with one click on the pump..
 You may want to watch the timing with a strobe when the Rs increase , as I would suspect a timing change increasing the Rs more than the new pump setting. You may have one broken spring on the mecahnical advance ...giving early advance, which would equal higher RPM..

?

[n/a]

Hi Rick,
Check the simple things first, as Joe Alexander suggests, before messing with other things.  I'd bet that you have a fouled spark plug, not uncommon if your fuel mixture is too rich.  The fouled plug would explain the stalling,the fuel smell, and the perceived loss in power.  I believe that a "searching" idle is usually the result of an overly rich fuel mixture.

Check to make sure that the linkage isn't sticking.  Use some WD-40 to clean away the junk and buildup.

Lastly, there is an adjustment for fuel richness on the injection pump.  Adjustments must be made with the engine OFF.  But, before you attempt any fuel adjustments, you need to be sure that your plugs, points, timing and dwell are correct.

Keep us posted as to your progress.

Best regards,
Don

[n/a]

Hello Rick,
I sent my previous post before you posted your most recent update.

Tell your mechanic to cancel that rebuild.  The fix is done very simply by removing some shims.  Ask Joe Alexander for more advice on this.

quote:Originally posted by RickInTex

Update:
  He's tried adjusting the mixture and says he's done this as far as it can go, and it's still too rich.  Dallas TX
1967 250SL, 4-speed

Good luck,
Don

[rwmastel]

quote:Originally posted by RickInTex

I kind of reached the limits of what I can do and took it in this morning to my mechanic.  He's confirmed that ignition seems to be fine and timing correct, but it runs way too rich.  He's tried adjusting the mixture and says he's done this as far as it can go, and it's still too rich.  ... he's thinking that the injection pump needs to be rebuilt.

How competent do you believe your mechanic is?  Have you been using him for years?  Does he work on the 1960's vintage MB Fuel Injection a lot?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[RickInTex]

Rodd, et al:
I've worked with this shop and mechanic before, and they seem to know what they're doing; I'm also talking to Will Samples, who's worked with them before, and the shop is in touch with Pacific FI.  Will feels that there are lots of cheaper and more likely causes for my idle and stalling problems than the injection pump:  CSV, but also warm running device, relevant relays on these; starting relay on inj. pump; broken or weak advance springs in distributor; problematic condensor.  I'm trying to chase down all other possibilities before rebuilding the pump.  I'm putting everyone's suggestions into the list as well.


Rick
Dallas TX
1967 250SL, 4-speed

[RickInTex]

Just got off phone with my mechanic.  I'm encouraged by him, but not what he told me.  Ignition is fine, distributor fine, csv fine.  He tried adjusting fuel mix screw, with no effect, and it's clear that the rack doesn't return.  The pump, he feels sure, has never been rebuilt within living memory, whatever adjustments were done by the previous owner.  It seems, in other words, that a rebuild is in order.


Rick
Dallas TX
1967 250SL, 4-speed

[RickInTex]

Took the plunge today and committed to a pump rebuild.  It wasn't in my plans for the car this year, but it seems unavoidable if I want to cure my idle problems and stop the engine from running rich.  Let's hope I'm posting happy news when I get it back!

Rick
Dallas TX
1967 250SL, 4-speed

[Ricardo]

Hey Rick
I'm reviving this thread to see what your final results were, weather your pump rebuild did the trick or if you are still dealing with stalling issues. Some words from experience are always appreciated.....
Richard

[RickInTex]

Thanks for prompting me, Richard.  I should've let everyone know how the story turned out, but I've just finished moving and it slipped my mind.  

In short:  it's running great, although getting it there turned out to cost a bit more in time and money than I'd anticipated--a pattern I'm accepting with this car, after a year of ownership.

A bit longer:  with a rebuilt pump, the stalling went away, the mixture is spot on, idle is stable at about 800, and it runs terrific.  Even mileage is improved; I get 14-15 in city driving, even though I find myself pushing it harder than before, since it's so much fun.  My only gripe is that now that summer is here in Dallas, with no a/c I'm limited to early morning or evening top-down drives.

Longest version:  A couple surprises along the way meant that it was late April before I got it back.  First, there were problems connecting the fuel lines and linkage to the new pump; evidently someone in the past had done some . . . eccentric . . . work on these connections, presumably when the 250 engine was put in to replace the original 230.  So, some searching to get the correct parts (closest supplier was in Germany, apparently).  Once these arrived, the pump went on, and the car ran terribly and fairly soon wouldn't start at all.  Investigation led to the conclusion that the new pump was itself bad.  Hard to believe, but even the supplier agreed it had to be.  So another pump ordered, which arrived (by ground, of course; high altitude will ruin it, I was told, so no air-shipping).  On goes the pump, it runs great, I pick it up, and I smile.  

Coda:  One week later I get hesitation, hiccupping, roughness, loss of power.  Given my recent history, I don't even think about the simple things--I can only imagine worst-case scenarios that will me more time without the car.  I take it in, and it's all instantly cured by a quick tightening of a plug wire that was loose from the boot.  Could've done it myself, had I kept my wits about me instead of being alarmist.  But, a Happy Ending.

The new pump, I have to say, is a lovely piece of machinery.  Once I get my digital cam back from its borrower, I'll take some pics and post them.

Rick
Dallas TX
1967 250SL, 4-speed

[Ricardo]

That's great Rick! Glad it all worked out. Hard to believe a fresh rebuilt pump would be defective, you must have been convinced you had some other major issue  
That's where I'm at....my pump was rebuilt last year and I'm now considering that it may be the cause of my sputtering, since nothing else seems to work  :evil:
Richard
'67 250 , 4 speed
#1834 May 3/67

[Ricardo]

I found my problem and it wasn't the pump! I decided to check my injectors and the first one I pulled was a replacement that I installed last year. It was dribbling fuel without a spray. Turns out there was a fine hair like piece of wire coming from the screen on the input side and hanging through the actual port. Pulled it out and the screen layed down in the bore and I got a nice spray pattern.
Voila the car runs like a top again. I knew no.6 was running a little rich, but I thought it must have something to do with the new R2 injector, the rest being old R1's....nope just a piece of crap (as Neil Young would say)    
That's me and the wife there
Richard