Advice for Cold Start and Warm up settings please?

[Ben]

I have ensured that the timing and dwell are spot on, the plugs, cap, rotor and points are new and the wires are good, I have checked the mixture (4%CO hot), the CSV doesnt leak and DOES squirt when cranking, yet I still have a few small issues.

Firstly from cold it will always fire up in around 3 seconds, but ALWAYS stall, then when I repeat it will fire again but threaten to stall again, yet it manages to keep running.

This is to do with the lines not being pressurised , right ? What's the most effective and/or cheapest cure for this.

Then after this the rpm's will rise to about 950rpm at which point it will hunt up and down about 50rpm's untill fully warmed. I have discovered it is running slightly too lean at this warm up stage as disconnecting the fuel pump rod and moving it by a fraction results in perfect high cold idle. Moving the throttle air rod results in a drop of rpms.

So its lean when cold. Is it possible to richen it up ONLY whilst cold ?  If I ADD a shim under the air valve this will richen it up but throw out the hot idle CO also wont it. And if I add shims but adjust the screw on the back of the pump so the CO reaad correct when hot then I have just undone the effect of adding the shims ??

This isn't a major problem but if there is a nswer i'd try it !

Anyone ??

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

[Naj ✝︎]

Ben,
Does the cold start magnet (solenoid) on the back of the F.I. pump work?

naj

65 230SL
68 280SL

[rwmastel]

quote:Originally posted by Ben

This is to do with the lines not being pressurised, right?

Ben,
Have you done fuel pump tests for flow rate and pressure?

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

[ja17]

Hello Ben,
It sounds like you are getting very close.  As naj mentioned, check the cold start magnet on inj. pump.
Next if  the ball check valves in the injection pump are worn fuel will drain back out of the injection lines. The engine will start for a second then die until the fuel injector lines are fuel filled again. This may take one or two starts.
These check valves can be changed easily by loosening the metal injection lines at the pump, remove the 19mm fittings, and thread a special tool or metric fitting onto the check valve and simply pull them out. (I found a metric clutch line fitting which was the correct size  to thread onto these checkvalves.)
I am not sure how expensive these check valves are these days. The replacement valves are supposed to be larger diameter and improved. The  nylon-like seals should be replaced also. If someone can supply a Bosch number for these they probably can be ordered from a Bosch outlet for a lot less.
The later BBB has a description of the job on p 07-13/1 and 07-13/2. Don't let the special tools scare you, they are not really needed.
The R20 and R21 injection pumps were the last with the small check valves. Later puumps had the larger 4mm diameter check valves which can be identified by the groove around its circumference.

Joe Alexander
Blacklick, Ohio

[A Dalton]

Your pump should have the old style cone valves
 The replacement ball valves are Benz Part # MB  000-074-17-15

 The start sol. on the pump does aid in start by moving the rack foward anytime the start circuit is energized, [ regardless of temp], but only with starter..nothing during run. You can check that with a test lamp or screw in pump rack just to verify it's operation. If you find that is not working, a fix would help in a better/faster start , but this would have  nothing to do with your warm up running condition...
The warm up a/f mix is dependant on warm up thermo and you have found the mix to be lean .   What you want is for the thermo to cut off intake air at the air filter intake port between 65C and 70C .. you can verify  this by simply checking when it closes and checking  your temp indicator when it does .. if it is not in range ,  shim changes will bring it into spec range. It is pre-determined at the factory how much a/f they want throughout the warm up  temps [ declining as temp rises] and if the heat sensor is working, but out of temp range, [ +/-] you can not get correct warm up a/f mix as needed for that engine temp.
 In you case , I would do this test for findings .. if this proves to be in spec/range , then [ due to your case of leaness ] you want to be sure no false air is leaking during the warm up .. suspicions here are the throttle plate not completely closed and other vac leaks [ I always plug the booster line when doing this type of work, just to take that possible out of the equation]
 If anyone finds the same complaint, but richness caused [ vs lean], then a dirty pump intake filter is suspect.. an easy test here is to simply take the filter off as car is in the warm up range and see if the engine speeds up w/out the filter installed .. that would be filter confirmation .  
 

[Ben]

Okay thats great guys........thanks for the advice !

I admit I never checked the solenoid, basically because I never have anyone to crank when I'm testing !  I can see the test light at the CSV when cranking. I'll do this first !

Having ensured the solenoid is working next I'll check and play around with those shims and washers again, noting what I've done in case I need to revert to previous set up.

After that I'll figure out if those valves need replacing ! We have a Bosch agent hjere close to use but despite the fact that the same guy has run it for 30 odd years he said he's never seen a 113 pump or similar, so that doesn't inspire confidence !!

Anyway thanks again !

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