250SL won't start

[Mike Hughes]

Dan & Joe -

I put another 5 Gallons in the tank.  Now the fuel gauge reads just about full.  The engine fired up almost immediately but wouldn't keep running for more than 30 seconds or so. Repeated attempts finally got it running nicely for almost 5 minutes, enough to get it almost up to normal operating temperature, before it quit again.  The main thing is that it runs just fine - no stumbling when blipping the throttle and a nice tickover - when it runs!  I gave it a rest for a bit while I took a phone call and when I tried to start it up 15 or twenty minutes later - nothing!

The only filter that hasn't been inspected yet is the one in the pump, so I'll look there next.

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

[Mike Hughes]

Since my last post I've checked the screen in the pump and it was clean as a whistle, then I drained the tank again.  This time 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 then 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 (even though I thought from the good flow that it is clear) and the smaller fuel return line with compressed air and cycled 1/2 gallon of gas several times through the tank, allowing it to drain out the open drain plug hole into a pan.  This collected a small amount of debris flakes that appear to be varnish, rather than rust.  I have not refilled the tank yet.  Next?

- 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

Since my last post I've checked the screen in the pump and it was clean as a whistle, then I drained the tank again.  This time 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 then 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 (even though I thought from the good flow that it is clear) and the smaller fuel return line with compressed air and cycled 1/2 gallon of gas several times through the tank, allowing it to drain out the open drain plug hole into a pan.  This collected a small amount of debris flakes that appear to be varnish, rather than rust.  I have not refilled the tank yet.  Next?

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

Hey Mike,
Did you check the small hole near the return pipe on the 'flower pot'?
Dr Dan describes it in the 'FUEL TANK TOUR' page 2.
Apparently it allows fuel to enter the 'flower pot' when the fuel level is low.
If a tank has been cleaned and re-lined it is often forgotten because it is tucked down under the return pipe.

http://index.php?topic=1712


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

[TheEngineer]

This may be duplicating someone else's suggestion: I'd try to rig an alternate fuel supply, like a container hung up high or a container with a pulse pump and connected to the installed fuel filter. If that corrects the symptoms then you can proceed to the fuel tank. Note that the fuel consumption is much less at idle.

[Ian45]

Just to say that I've noted all the suggestions for the problem with my car, for which I'm very grateful and will feedback as soon as I've tried some of them out.
Many thanks, Ian

Ian
1967 250SL
1998 SLK230
Derby,England

[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)

[ja17]

Hello Mike,

New points will seat themselves sometimes after initial installation. I usually install, test drive then re-check the dwell afterward.  Also make sure the rubbing block and/or the distributer cam  gets a bit of grease or else the rubbing block on the points will wear, closing the points.



Joe Alexander
Blacklick, Ohio

[Mike Hughes]

The cam was dry when I pulled the cap and dust plate.  Blue Streak makes a distributor cam lube that I have used on my M.G.s for many years.  I put some on the cam after I found the points closed.  I only opened up the points by eye, just to see if this might be the problem.  What should the dwell be?

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

[ja17]

Hello Ian, .
The dwell for the 250SL is 38 degrees plus 3 degrees or minus 1 degree (new).  Used points can read 34-41 degrees.

Joe Alexander
Blacklick, Ohio

[glennard]

Ian, In regards to the flow rate out of each of the FI pump nozzles.  Say you burn 4 gallons per hour(60 mph at 15 mpg), that means each individual FI pistons is pumping about 1 oz.(+/-) per minute.  At 4000 rpm that is 1/4000th of an ounce per stoke.  Pretty fine metering.  You will not see much each stroke- but you can feel the pressure with your thumb.

[Joe]

quote:Originally posted by glennard

Ian, In regards to the flow rate out of each of the FI pump nozzles.  Say you burn 4 gallons per hour(60 mph at 15 mpg), that means each individual FI pistons is pumping about 1 oz.(+/-) per minute.  At 4000 rpm that is 1/4000th of an ounce per stoke.  Pretty fine metering.  You will not see much each stroke- but you can feel the pressure with your thumb.

Uh, given the car is a four-stroke, wouldn't that be 1/16,000th of an ounce per stroke?
Joe

[glennard]

Whoops! Joe and Ian.  At 4000 crank rpm, the FI pump is going 2000 rpm in sync with the cam.  So, at an ounce per minute, it is 1/2000th of an ounce per FI piston stroke - I think?.  Pretty fine metering either way.  The HELIX strikes again.  Pagodas had it before DNA.

[Naj ✝︎]

Aah, but then there are six cylinders and six nozzles to feed....

Oh,  :evil:  OK, three per RPM

naj

68 280SL

[glennard]

How about starting with 0.00075 oz. delivered on each individual FI pump piston stroke with the engine at 4000 crank rpm(2000 rpm on the FI pump cam).  So,  0.00075 oz/stroke x 6 strokes/rev x 2000 rev/min x 60 min/hr x 1 gal/132 oz. = 4 gal/hr fuel consumption.   Nanotechnology Pagoda style.   Each engine/pump will have its own oz/stroke vs engine rpm curve.   Flow rate difference between injectors need to fall within BBB guide lines.  Takes about 1333 FI pump revs to fill a shot glass.

[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)

[Ben]

Mike.................glad you found the problem. i had the same thing about 4 years ago. I installed new Bosch points and after a day or two the car ran crap.

Eventually looked at the dwell, I had spent quite some time setting this up correctly so i felt it couldn't be that. Anyway it was the new points, the contacts never hit eachotehr correctly.

Obviously Bosch made in the far East and poor quality.I stuck in another set and no problems !

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

[hands_aus]

quote:Originally posted by 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)

Mike,
Seems like the problem was actually the condenser.
Good idea to replace the pitted points.

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