Massively rich mixture

[twistedtree]

Thanks to everyone's help I got the throttle linkage problem sorted out on my '64 230.  After a bunch more fussing, I finally got it started, but it barely runs.  A split linkage test shows a massively rich mixture - I can get it up to around 3000 RPM just by opening the throttle flap and with the FIP lever against it's idle stop.  Here's what I've done so far:

- Performed a complete linkage adjustment

- Checked CSV for proper operation, especially leakage.  It checks out fine, and there is no leakage.

- Removed fuse #6 to kill power to both the CSV and the start enrichment solenoid on the FIP.

- Put an M4 bolt in the rack end and confirmed that it moves freely.  I can push it in and it will gently spring back.  And I can pull it out and it will stay out.  Moving the FIP control lever doesn't seem to change the rack position at all, but I'm not sure if it should.  Does this sound like normal operation?

When running, if I push the rack in it leans out the mixture and the engine speeds up.  I'm not sure what to make of that.

I think my next steps are:

1) Get the engine warmed up and confirm that the WRD is shutting off properly.

2) Change shims on the Barometric compensator to lean things out.

3) As a last resort, start adjusting the rack screw, but I'm very reluctant to do that until I've ruled out everything else.

Anyone have any thoughts or suggestions?

[ja17]

Sounds like your WRD is stuck. Do not change any shims until you make sure it is working.

[twistedtree]

I fixed and/or ruled out a number of things today, but I still have a massively rich mixture.

Checked the oil level in my FIP.  Others have reported that over-filled reservoirs can result in excessively rich mixture.  The oil was indeed over filled.  I pumped out about 300ml, and replenished with about 150.  It now reads full on the dip stick.  The oil I pulled out smelled of gas, so I'll need to monitor it, but that's a problem for another day.

My WRD was indeed seized up and I got it cleaned up, tested, and reinstalled.  Ran the engine until it warmed up and the valve shuts off properly. 

Unfortunately, none of the above made any appreciable difference.

Next I tried removing all the shims from the BC.  This made a noticeable difference, but I can still open the throttle flap to admit extra air bringing the RPMS up to 2000-2500 RPM.  At that point more air causes it to start to stumble.

Next I removed all the shims from the WRD.  These are the oval shims between the WRD and FIP - I have an old-style WRD with no internal adjustments possible.  This made a slight improvement, but not much.

Last, just as an experiment, I backed off the idle mixture a total of 20 clicks, but it made no significant difference.  I plan to set this back to it's original setting before doing anything more.

So what's next?  I remember a post by Dr Benz (I think) about a FIP that had been installed at 20 BTDC instead of 20 ATDC and the result was a hugely rich mixture.  I believe this engine is newly reinstalled in the car, so this is possible.

Other than that, I don't think there is anything left to do except start adjusting the rack screw.

How would you experts proceed?  Go through the long process of removing the FIP to confirm the timing, or start adjusting the Rack screw.

[jeffc280sl]

Check your barometric compensator. 

[Benz Dr.]

Yeah, I did post about that quite a while ago. 20 degrees ADTC is a long ways from 20 degrees BTDC. I believe you will be removing this pump anyways so turn the engine over to 20 ATDC before you pull the pump off and check the timing marks on the pump. In the remote chance that this is the problem you can always put it back on the engine and try it. I believe however, that your pump is worn out.
 
You said the engine has been rebuilt? What about the IP? When I rebuild an engine I have the IP, injectors and CSV looked at. Injection pumps have a way of wearing out and going rich. Fueling the engine oil in a rebuilt engine isn't a good idea and I'm trying to avoid that.

  If everything you try gains you nothing, then it's time to have the pump looked at. If it's never been done, my guess is that it's very much out of calibration. Aside from general tips about external adjustments, none of us are going to be able to help you. Our hints are fine for pumps that have a stuck WRD or some other easily fixed problem, but I believe yours is so far out of adjustment, it needs to go in for servicing.

You'll be happy you did once it's fixed.

[twistedtree]

Check your barometric compensator. 

As best I can tell the BC is OK.  I have the one off this car, plus another full injection pump complete with WRD and BC in my parts collection.  I've compared both BCs and they both have the same pin extension.  I've tried the BC with all washers removed, and that improved things (as expected) but it still has a long way to go.

I think next I'll play with the rack adjustment, keeping track of the changes I make so I can get back to where I started.

If that fails, I'll pull the IP and check the alignment.

If the alignment is good, then I'll probably try the spare pump that I have.  It's condition is unknown (just like everything that I've got), but I don't think I have much to lose other than a bit of my time.  I've got 6 other pumps too, all in unknown condition, but I don't think I want to randomly try them all.

As for the history, on one hand I have none and can assume nothing as this is all part of a giant barn find.  On the other hand, the previous owner had worked extensively on MBs and I believe generally knew what he was doing, however he's quite old and I think was starting to overlook things.  I say this because I've come across a few things that were quite messed up.  He also was apparently quite skilled with FIPs and had built a calibration rig.  This car supposedly had a new (rebuild, as it's the original # motor) engine.  Based on what I've encountered, I'd guess it's never been run, and this "new" engine could have been done 10 years ago.  The FIP had a tag on it with handwritten notes which I'm guessing are his calibration notes, so it's very possible that he worked on the IP prior to installation.

I think the bottom line is that I need to assume that everything has been worked on, and anything could have been done wrong.

[ja17]

I think everyone has assumed you have gone through "the linkage tour"?  

[stickandrudderman]

He states in his OP that he's done the linkage game....
The best and quickest way to get to the bottom of this is to remove the pump and check the timing. If the timing is OK then install the pump on an engine known to be running well and see if you can introduce the problem. If you do then you know you've got a pump that needs attention from a specialist.
Personally I would just send the pump for testing. If the pump tests OK then there shouldn't be much charge from the specialist, and if it's not then you're on the right path anyway....

[twistedtree]

Yes, linkages are all sorted out, and it was the most messed up I've ever seen - but all correct now.

My operating theory right now is that the previous owner recalibrated the FIP when the engine was out, and that it either wasn't reinstalled correctly or just needs a major initial adjustment.  The car has pretty low mileage (60k) that is well documented all the way back to the original owner, so a badly worn pump doesn't seem likely, though others with more experience than me may feel differently.

My next best guess is that the PO worked on the pump and did something wrong that can't be corrected with adjustment.  Attempting to adjust will confirm or dispel this theory, and lead me as a last resort to swap for another pump and/or send this one out for service.

I want to exhaust all adjustment possibilities, before I remove the pump for swap/service.  On the way out, I'll check the alignment and if it's way off then I'll correct it and reinstall.  Otherwise the pump stays out.

[paults1]

I have heard that many times a common error is to re-install the FI pump at 20 degrees off.  I don't know if this would cause a rich mixture.

[twistedtree]

Here's the latest.

I checked the fuel pressure and it's fine (about 12 PSI).

I restored the idle fuel to its original setting, and replaced the shims under the BC.

Then I went after the main rack adjuster.  After a total of 22 clicks CW, the engine runs pretty well.  Not dialed in by any means, but it runs, revs, and otherwise runs OK.  It's still a bit rich, but I then discovered that I had maxed out the rack adjustment.  From this, I conclude there is a more fundamental calibration problem with this FIP.

Next I removed the FIP after setting the engine to 20 ATDC on #1.  After the pump was out, I checked the alignment marks and they are correct - mostly.  It might have been off by one cog, but no more.  I also might have moved it a bit during the removal process.  It's definitely not off by 40 deg which would be the case if it had been mistakenly installed at 20 BTDC.

So, this FIP needs to go back to Santa's Workshop for proper calibration.  I'm guessing the PO wasn't quite so good at calibration, or at least made a significant error on this one.

In the mean time, just for kicks, I might try installing the spare R11 FIP that I have.

[twistedtree]

Here's a quick follow up on this topic.  I got my FIP and CSV back from H&R a week or so ago and today got in installed.  I also replaced the fuel tank, changed the fuel filter, changed the engine oil which reeked of gas from the leaking FIP, and changed the oil filter.  The oil filter was a bit of a diversion because I discovered it was missing a key internal part and hence not really working before.

With all that sorted out, I bled the injector pipes, tightened them up, and presto, the engine fired right up.  It sounded pretty darn good - way better than before.  Now I get to go though and do a proper tune up to really get it running right, but at least the FIP, CSV, and WRD are in tip top shape.

The best part is that 3 of my 4 SLs now move about under their own power.  I've been getting pretty tired of pushing, shoving, towing, and winching them around.

Oh, and the pump looked spectacular after Hans's work.  It looked brand new with new screws, everything plated and shiny, and little paint dabs marking the screws.  I couldn't be happier, and he turned it around in less than a week.

[glenn]

 re: oil filter 'missing key internal part'.
Might that be the washer on the stub at the top of the cartridge?  That's probably missing on 50% of engines......

[twistedtree]

Yup, that's the part.  Fortunately I have three other oil filter assemblies in my parts collection so I was able to salvage one and keep going.