engine stalling after good rpm run

[Sven]

Need some help.  Drove my 68 280sl for the first time in about 6 months.   Took it out, filled the tank, drove gently for a few miles, then hit the interstate for 10 miles or so at 70 mph, and it ran great.  once off the interstate, the car stalled three times in only 2 or 3 miles.  each time, it wouldn't start right away.  let it sit for a few minutes (3-5), then it would start and run just fine.

What's going on? i have had the car running for a year or so and it never did this before.  could it be vapor lock?  any thoughts would be most appreciated.  thanks

[ja17]

Hello Sven,

Sounds like the ignition points may have closed up on you. Re-gap them if so.

Joe Alexander
Blacklick, Ohio

[Naj ✝︎]

Hello, Sven,

 

quote:could it be vapor lock?

I would also check that the fuel return line is not clogged up, especially the bit in the tank. The lines rust from the inside and the debris ends up in the tank.

http://www.sl113.org/forums/uploaded/ja17/200611475414_fuel%20tank%20with%20fp%20ill..JPG

naj
68 280SL

[hands_aus]

There is a lot of this about.

Local friend is going through the same thing. He has been re-miss about driving his 230sl.
The tanks is being cleaned out with the hope that new filters will also help his cars condition.

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

[Sven]

update:  drove the car today for about 20 miles. drove fine, but will stall at idle.  i have a vacuum leak, so as long as i am applying brake when idling, it will not stall. let off the brake (i.e, true idle) after warmup, and it will stall. also, kickdown is sticking.  this started the same time i started after the first stall yesterday. don't know if they are connected or not (kickdown stuck for a while last summer). any better clues for the experts?  i dealt with the fuel system last year (new lines, replacement tank, new pump, inline filter) so i think the fuel system is good, so am leaning to joe's points needing to be gapped.

[Shvegel]

A couple of things cone to mind:
If you kickdown is sticking you might be dragging the engine down causing the stall.
Fuel in these days of high fuel prices is becoming less and less "gasoline" and more and more a blend of evapoative crap. It is becoming far less stable than it was which means that you might want to drain and fill your tank. What could be happening is that your car is stalling and you are indeed experiencing a form of vapor lock due to some increased volitility in the fuel in your tank or your injector check valves are dirty or shot.

[hands_aus]

quote:Originally posted by Sven

i have a vacuum leak, so as long as i am applying brake when idling, it will not stall. let off the brake (i.e, true idle) after warmup, and it will stall. also, kickdown is sticking.  this started the same time i started after the first stall yesterday. don't know if they are connected or not (kickdown stuck for a while last summer). any better clues for the experts?  

The auto transmission has a vacuum connection to the Modulating Pressure Diaphragm so if you are having vacuum problems it seems highly possible you will have auto trans problems too.

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

[Ben]

I would checkj to see if the 3 position solenoid is still working correctly !

Also concur with the vacuum leak stuff !

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

[Sven]

update: haven't had the opportunity to do anything of merit.  however, started the car yesterday just to see how it started.  it took a relatively long time (5-6 seconds) to start.  when it stalled on me this past weekend, it was also taking about the same amount of time to restart (after sitting 5-10 minutes of course).  this relatively long crank time is new.  up until last weekend, it would always start after only a second or two of cranking.  leads me to believe it could be an ignition problem, that then propagates the shifting/kick-down problem. does that seam reasonable, or can the shifting/kick-down problem pull down the engine and cause it to stall?  chicken vs. egg.

as always, thanks in advance for any thoughts or suggestions.

[Ben]

It seem logical to check the dwell and timing before going any further IMO, and before making other adjustments/assumptions !

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

[Sven]

update: seems to be the fuel system after all. I have a clear in-line high performance fuel filter between the tank and the rear fuel pump. When the car stalled today on the way home from work, I looked at the filter and was able to observe it empty, slowly filling back up over a few minutes.  Obviously, there is a blockage in the tank, but it only happens under low fuel demand (idling at a stop light).  

btw, i replaced the tank a year or so ago (old tank rusted and full of holes) with a used tank that appeared relatively clean and rust free.  Any hints or easy approaches on clearing the blockage?

[ja17]

Hello Sven,

Assuming fuel delivery pressure and quantity is correct try the folling procedure;
Remove the fuel tank drain strainer first make sure it is clear. Remove the fuel line between the elec. fuel pump and tank, run a steel cable, long brush or such down the fuel outlet tube of the tank to the drain opening at the bottom of the tank. Also snake the fuel return line. It must be clear into the "flower pot".  You may want to remove the fuel gauge sender so you can watch what is going on in the tank.  Also remove the fuel line intake fitting going into the electric fuel pump it has a screen it it which is easily clogged. Finish by blowing compressed air throught the fuel tank tubes.

Clearing the fuel intake opening in "the flower pot"  requires a little more work. The opening is directly below fuel return line going into the "floweer pot" This is deep within the fuel tank. It can be cleared with a long compressed air nozzle or wire from the fuel gauge sender opening. However you will need to know exactly where to find the opening. view the information on the "fuel tank tour" first.  I will post a picture of it if you cannot find one on "the fuel tank tour".

The fuel tank vent must also be functional. Test for a problem here simply by loosening the gas cap the next time your car shuts down. It should re-start after loosening the cap.

Joe Alexander
Blacklick, Ohio

[Mike Hughes]

Hi, Joe -  I'm following this thread, too, as my 230SL quit running under similar circumstances.  I originally posted my problem in the topic "250SL Won't Start."  So far I've cleaned the screen in the tank, checked the screen in the pump (which was pristine), and changed the main fuel filter at the engine.  The second time I drained the tank (after cleaning the in-tank screen and refilling) the flow out the tank to pump line was like a garden hose until the last 2 gallons, which was barely a trickle.  Occasionally, one would hear  some gurgling within the tank and there would be a greater flow for a short time, followed by more trickle.  After the tank was empty I blew out both the large fuel feed line and the smaller fuel return line with compressed air.  Next?

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[ja17]

Hello Sven and Mike,

As Dan has mentioned in past posts, make sure the return line going from the engine compartment back to the fuel tank is clear.  Remove the gas cap and blow some compressed air from the engine compartment back into the fuel tank, make sure the gas cap is off!

Now onto the flower pot.  Assuming, fuel pressure and delivery is correct, all fuel lines are clear, fuel tank screen is clear, electric fuel pump screen is clear, main filter is clear, and the fuel tank vent is clear you can check the "fuel fill port" in the flower pot. this is independant of the fuel return line. Look closely at the photo. the port is along side and beneath the fuel return line.  It does not take much dirt to plug it up since it is in the lowest part of the entire fuel tank. You cannot get to it unless you remove the fuel sending unit and go in from above. Use a long compressed air nozzle to blow it clear or a wire to clear the port. Caution, fuel vapors are dangerous, use a safe trouble light or flashlight. Sparks from lights and static electric must be avoided. It's best to do this work outdoors with plenty of ventilation, good sealed containers to hold fuel, with fire extinguisher and garden hose near by.

Look at the photo of "flower pot" closely to find the port and learn how the fuel deliver and return lines work.


Download Attachment: fp.JPG
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Joe Alexander
Blacklick, Ohio

[rwmastel]

Sven,

Read these threads:

http://index.php?topic=1712

http://index.php?topic=5639

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

[Mike Hughes]

The 230SL is running again, just as if nothing had happened.  This after cleaning and/or replacing all three fuel filters, Checking that the fuel pump was delivering fuel, blowing out the return line, and removing the fuel sender and poking any debris out of the flower pot orifice.  Satisfied that fuel delivery was no longer a problem, the engine still would not fire for more than a few seconds.  Turns out that the plastic rubbing block on the points had worn down and they were closed up!  A minor adjustment and she is purring again. Even so, I am a bit mystified why this would be the resolution to a problem that clearly seemed to like a fuel starvation issue...  it simply behaved like it was running out of gas!

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[hands_aus]

quote:Originally posted by Mike Hughes

Even so, I am a bit mystified why this would be the resolution to a problem that clearly seemed to like a fuel starvation issue...  it simply behaved like it was running out of gas!

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

Mike
When the rubbing block of the points wears down this changes the Dwell angle of the timing.
So the car was not running under ideal timing.
Are you planning to change the old points for new ones?

I had this exact problem occur over night...car going great before switching off, next morning engine would not start.
I checked the points gap and they were almost closed up at 0.003" instead of 0.012".
Points changed and car almost jumped off the floor of the garage when started.

2 weeks later I replaced the points with a Pertronix unit and have never had to worry since.

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

[Mike Hughes]

I show the car occasionally and MBCA judges look for non-standard stuff under the hood, so points are fine with me.

Of course my real issue is that it stranded me again yesterday after going only 8-9 miles!  I had just set the dwell at 38º and was road testing.  Acted just like it was running out of gas (with a full tank!), intermittently cutting in and out and then just dying in the middle of the road in less than 15-20 seconds.  Fortunately I had a little inertia and some quick reflexes and was able to coast into a handy parking lot.  

I'm thinking that I may have a bad condenser.  There is one on the side of the distributor but there also seems to be another one on the coil, something I've not encountered on any of my British iron.  What is its function?

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[hands_aus]

quote:Originally posted by Mike Hughes

I show the car occasionally and MBCA judges look for non-standard stuff under the hood, so points are fine with me.

Of course my real issue is that it stranded me again yesterday after going only 8-9 miles!  I had just set the dwell at 38º and was road testing.  Acted just like it was running out of gas (with a full tank!), intermittently cutting in and out and then just dying in the middle of the road in less than 15-20 seconds.  Fortunately I had a little inertia and some quick reflexes and was able to coast into a handy parking lot.  

I'm thinking that I may have a bad condenser.  There is one on the side of the distributor but there also seems to be another one on the coil, something I've not encountered on any of my British iron.  What is its function?

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

Mike,
The condenser on the side of the coil is for radio noise suppression.
You could disconnect it and do a trial run.

Can I ask? have you checked all the screws on the ballast resistor and the coil and any other electrical connection in the start/run wiring of the engine including the ignition switch?

There was a loose screw on one side of my ballast resistor which caused lots of problems for me on the motorway. Driving at 100kmph, hit a bump, engine spluttered and died, hit another bump engine started again and off i went as if nothing wrong, hit another bump same thing, eventually stopped.
I thought about it and figured it had to be electrical. Checked all the screws and found the loose one had no lock washer under it. Added a lock washer, tightened it up and no more problems.

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

[Mike Hughes]

One of the first things I did was bypass the ballast resistor - and I did find one lock washer missing, too!  When it was running, it ran the same with or without the ballast resistor in the circuit.  I also checked all the coil and distributor connections, but I haven't checked the ignition switch connections.  However, the fuel pump continues to whirr merrily away back there when the engine stalls and won't restart, so I think that I probably have continuity at the switch.

quote:Originally posted by hands_aus
Can I ask? have you checked all the screws on the ballast resistor and the coil and any other electrical connection in the start/run wiring of the engine including the ignition switch?

There was a loose screw on one side of my ballast resistor which caused lots of problems for me on the motorway. Driving at 100kmph, hit a bump, engine spluttered and died, hit another bump engine started again and off i went as if nothing wrong, hit another bump same thing, eventually stopped.
I thought about it and figured it had to be electrical. Checked all the screws and found the loose one had no lock washer under it. Added a lock washer, tightened it up and no more problems.

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

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[Mike Hughes]

I am finally able to close the loop on the stalling/won't restart issue with my 230SL.  It was a set of nearly brand new points that were so badly pitted that they would read a reasonably correct 35 degrees one moment and effectively be closed up completely the next.  I discovered this after checking continuity of the ignition circuit all the way from the switch to the coil and the distributor.  The engine would fire, run for a few seconds and quit.  Once it quit there would aften be no spark again until I "fiddled" with the distributor.  Then it would fire up, run for a few seconds to a minute and quit again.  Hooking up a dwell meter to the distributor would show a reasonably normal reading while the engine was running but it would flicker towards 0 degrees during any intermittent misfire or go straight to 0 degrees when it stalled out.

I pulled the points out to examine them and found a HUGE pit on one contact and corresponding cavity on the other.  After replacing the condenser, filing down the pit and reinstalling and adjusting the points I now have no misfiring or stalling, and the stumbling that I was encountering when putting it in gear and/or starting off from rest at a stop sign or traffic light is also gone!

I'll be picking up a new set of points and installing them on the weekend.

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[Benz Dr.]

I like to run a slightly different dwell angle than what's called for - usually about 40 to 42 degrees. This will make the points close up a bit and a lot of higher RPM problems can be cured this way. The wider you set the points the the more they will bounce in a worn distributor.
I find that any wear inside of the distributor will make the points bounce above 3,000 RPM. You can't see this with a timing light; only a distributor tester will find these problems. Wear in the bearings or main shaft is the usual problem but you can also have wear at the moving plate that the points sit on as well as
the shaft that holds the rotor.

I did a dual point distributor for a 300SL last week and it had only minor wear at the top bearing but the cam was really worn. This unit is very different than anything you will ever see because it has dual points and dual coils. The cam only has 3 lobes on it so each set of points feeds 3 cylinders fed by individual coils. It's possible to have 3 cylinders fireing sooner than the other 3 and that was happening here. These cars have 2 carbon brushes inside the distributor cap so the rotor is sort of cone shaped with one brush touching in the centre as usual and the other rubbing on a ring inside the cone of the rotor. The rotor is held in place by a screw and this is were the problem started.
Under the rotor is a felt wick that needs to be oiled but probably never got lubed. Eveything was rusty and tight in there causing wear. The late 280SL has the same problem - few people oil the wick because the points last so long in later ignition systems.

You won't find replacement parts for a 300SL distributor so I took it apart and placed the end of the shaft where the rotor would fit on top of a slightly opened vice. The metal on this shaft is very hard so it's very hard to peen it but light taps with a small hammer will start to spread the metal a little bit. I test fitted the two pieces until it started to go tight and then filed it a bit to smooth off any rough edges. Owner claims it's never run this good.
 
These distributors have a 86 degree dwell angle ( done by setting each set of points 43 degrees )  and will run up to 8,000 RPM without any point float. Before I rebuilt it I only got about 4,500. Wear will cause the points to close up and the shaft will vibrate causing the points to bounce.

You can go to electronic ignition and still have running problems such as sticking fly weights. Move the shaft sideways to see if you have any play. Only complete tear down will tell you if the cam shaft is loose on the main shaft.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[ja17]

Hello Dan,

I think a new ditributor cap and rotor for a 300SL Roadster is over $1,000.00 these days from Mercedes!!
It is a strange looking animal with two coil wires going into it and three lobes on the distributor shaft! As you know besides setting the dwell on each set of points separately, you also need to get the points firing exactly 120 degrees opposite each other!

Joe Alexander
Blacklick, Ohio

[Benz Dr.]

Joe,
wouldn't that be 180 degrees opposite each other? The distibutor tester showed that one set had closed up and when I set it back to 43 degrees all 6 hit exactly 60 degrees apart. This is VERY imporant in dual point units with 3 lobe cams ( 6.3 has four lobes ) so that all cylinders fire at the same place in rotation. It's critical on a 300SL with cylinder heads over $30,000.00

I check this on the type of distributors our cars use but it can't be fixed unless the cam is changed to one that's not worn. 2 or 3 degrees difference between some cylinders isn't uncommon. A 6.3, 300SE,or a 300SL is a much better unit than what's used on our cars. The precision is very high on the 300SE unit which is what I use on the Red Rocket. This dual point unit runs at 52 degrees. I found a BMW cap that will fit this distributor so I can use regular plug wires. Points are the same as used on the 6.3 and kind of exspensive at about 25 bucks each!

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[ja17]

Hello Dan,

I was figuring 120 degrees at the crankshaft (half the rotation of the cam and distributor). At the distributor, you are correct it is 60 degrees.

Good to know your tip about the BMW distributor cap!



Joe Alexander
Blacklick, Ohio