230SL engine will not idle after warm up

[Ron]

OK, I did my homework and searched the site, but sill no luck, so I'll ask the group.  I cannot get the engine to idle.

History: Car purchased years ago with engine on pallet, "rebuilt".  Installed (with help from this site), it ran well, but leaked oil at rear main, blue or white smoke (depending on position of certain stars - that is random).  This winter and spring I took it down to the bare block with the help of a local mechanic.  Pistons, crank, bearings looked good.  I changed cam (old one pitted), both were proper number stamped on back, new timing chain, new lower sprocket, new rear main seal, all new Mercedes valve seals, rockers and ball studs, and proper injection pump (R11, sent out for new seals and calibration).  Plus all the missing bits and pieces were found and installed - the car is close to all factory pieces, just used.

Now:  engine in the car, it starts, runs well (no smoke or steam, no oil leaks) with high idle, until warm up, then it will not idle.  I've moved the idle adjust screw on IP in and out 20 clicks each way, with some minor changes, but still no idle, it just dies below 1000 rpm.  20 clicks lean means back firing out the exhaust.  Linkage checks out.  Static timing on the mark, but I can't keep it going long enough to check with a timing light.  Air bleed screw for idle has no effect. 

I'm about ready to remove the R11 pump and put back the pump it came with, R18, at least that one would idle.  Or send back the R11 pump to the rebuilder?

Any ideas?

[ctaylor738]

A couple of suggestions

- bump the timing a few degrees advanced maybe in two five degree increments and see if that helps
- try opening up the idle air adjustment

[michaelgread]

Check for vacuum leaks !!

[ja17]

Make sure your engine linkages are correct. Also have you tried adjusting the air screw on the intake manifold?

[Ron]

Thanks for the suggestions, and here's a bit of update. 

(I'm away from the car (Houston then Baton Rouge seeing family, and happy 4th everyone.)

Here's what i know from a week or so of intense trouble shooting.

1. Fuel adjust idle screw on IP has little effect, it was about mid point from rebuilder.  10 or so turns lean gets back fire out of exhaust.  10 to 20 turns rich gets backfire in intake? but no idle.

2.  The car will only idle, 1000+, cold.  When warm, it will die when foot off of accelerator.  Above 1200 rpm, engine is smooth, getting stronger up to 2,500, the most I'm going right now.

3.  Air control on intake manifold has no effect.

4.  Split linkage, throttle blade not connected, no idle with accelerator in different positions.

5.  Split linkage, IP not connected, no idle with accelerator in different positions.

5a.  I did do the linkage tour and they linkages seem correct. 

6.  I did find some air leaks in the manifold gasket and #3 injector pipe had leak at injector.  Both were tightened and that seems to have helped a tiny bit.

7.  Shorted across the ballast resistor, no change.

8.  Moved timing + and -, a lot.  This would change the starting characteristics, but nothing else.  (went to hard to start, hard to turn over, etc., but still no idle.)

9.  Since it seems to have too lean a mixture, I decided to add shims to the WRD to richen.  It had one 0.3mm shim under it.  I had two shims, one .3mm and another .1mm from the old pump.  I put in the .1mm, and left the .3 mm, so .4mm total.  No difference. 

10.  Then I did something probably not healthy for the pump, but it did tell me a few things.  The IP has the WRD held on with to slotted screws, and the shims are held tight by these two screws.  So I loosened the two, and tightened back until the shims and WRD were are just barely touching.  Then I backed off the 2 screws 1/4 a turn.  Tried car.  No change.  I did this many times, backing the screws out several turns.  NO change!  The WRD was about 1/8" off the body of the IP when I stopped.  So, mixture is not the problem in the usual sense. 

So I think there's something wrong with the pump.

11.  It could be installed (by me) 180 degrees off timing.  So using J.A.'s on the engine IP timing check, I'll find out next week when I return to CA.  (I did get the old pump on correctly a few years ago, so maybe I just missed something this time.)

12.  If the IP is installed with correct timing, I will continue to remove the pipes, and on to remove the pump completely.  Then I'll install the old pump (R18 and incorrect) to see if it idles.  If so, I'll send the new pump (R11) back to rebuilder for a checkout.  So next week maybe I'll have some sort of answer.

I ordered two sets of IP to block gaskets before leaving CA, so things will be ready to go when I returned next week.

Any other ideas would be greatly appreciated.

Ron

O

[wwheeler]

I am thinking that an out of time IP would run better at idle than at higher speeds? My IP was 30-40* out of time and it ran well at idle. Only when I accelerated at higher engine speeds did it start to buck. With the timing back on, the problem went away.

[ja17]

Seems to me that the rack is stuck in the IP.

Check for rack movement through the front access port.

[Ron]

hi Joe and wwheeler, I did check the rack, and it moves freely.  On some of the posts with IP 180 degrees off, I did see some folks complain of poor idle or poor low rpm running.

I'm back home now and will explore the pump timing then post again.  Ron

[Benz Dr.]

It sounds like a really big vacuum leak. Check your brake booster hose or you could remove it at the manifold and plug the port to see if it makes any difference.

[Ron]

It's running and idles.  It was a mixture of issues.

1.  (checking) Timing the IP via Joe A's method showed that the pump was in time.  But removing the #4 check valve was difficult.  I had to try several sets of pliers to get it out.  It was full of sludge, and the flukes? where rough and had corrosion.  So I used carb cleaner and fine emory to shine them.  Then I checked the other 5 valves, mostly ok there.

2.  Check for vacuum leaks (Benz Dr's and Michael Read suggestions), no problems uncovered there.

3.  Upped the setting on the butterfly plate screw, and was able to finally get it running with me out of the car, rough, but running.  Used timing light, finally, and it was too advanced.  Retarded back to proper setting, it ran at idle.  Throttle butterfly back to proper adjustment.  Now I need to play with idle on IP, and air screw on manifold, but I think it will come around.

Thanks to everyone for helping me think - I need lot's of help in that.

[Ron]

PS 'Discovered today the car has an incorrect distributor.  It has a vacuum RETARD distributor, so now I need to find a correct unit with vacuum advance.

[Ron]

After much detective work, i've determined my car should have and does have a "retard" distributor, as it has a vacuum take off on the throttle body at the bottom.  Many useful posts later, I discovered that for this car, the idle timing should be adjusted with vacuum applied, to 2 degrees retard.  I did so, the thing runs great, and now idles.  The linkage split tests, the air screw for idle speed, and everything else, all work as they should. 

Thanks to all who posted on this topic over the years, especially Dan C. and Joe A.

I could have never figured this out alone.

Ron