Cylinders 2 and 4 apparently not functioning

[duffelpud]

My 1967 250sl has never run perfect, but it has been running good over the last couple of months - that is up until about four mornings ago.  I started the car and could immediately tell that it was missing on at least one cylinder.  After pulling plug wires I determined the #2 cylinder was the culprit.  I checked for spark and fuel to the injector and both were good.  I then pulled the injector and swapped it with the #1.  #2 continued to malfunction.  I then determined that #4 was also malfunctioning.

History - The car had been stored for a number of years by the previous owner, and I am unsure of how often it was started or even turned over.  Prior to cranking it I cleaned the entire fuel system including the tank and lines, replaced the fuel pump and then had a mechanic inspect the injectors, replace points & plugs, and do the initial startup.  Since that time I've replaced the brake booster, shifting linkage grommets, water pump, adjusted the air intake butterfly valve to the correct 'closed but unstuck' position, fiddled with the idle mixture on the injector pump (without being able to tell that it had any effect whatsoever), and made repairs to the exhaust.  While the car has never idled smoothly, it has performed better over the last three months as a result of repeated 'Italian tune-ups'. About two weeks ago I noticed a decrease in power after flooring the accelerator during an outing - I had that 'ah-oh' feeling, but the next day the car seemed to run 'fine' again.  That was until the morning it started missing.

The car has been running rich but I've been unsure of where to start tracing down the problem.  Because of this I suspected possible carbon build up on the valves, but the 'event' seemed to come on rather suddenly, so I'm doubtful.  I'm unsure how to proceed at this point - compression test?  Sea Foam through the brake booster vacuum hose?

I welcome input from those wiser and more experienced than myself.

[twistedtree]

In no particular order...

- Confirm you have a good spark at both cylinders

- Check the compression, and inspect the plugs at the same time.

- Confirm you have fuel from the FIP.  Crack the nut that connects the line to the injector and crank the engine to see if any fuel emerges.

- Check for foaming in the oil resulting from antifreeze leaking into the oil.

If something suddenly happened, which is sounds like it did when you floored it, my guess would be a blown head gasket.  A compression test would confirm.

[duffelpud]

I'll do all of the above and report back this evening (including repeating a couple of the steps).

[duffelpud]

Cyls. 1, 3 & 4 (I stopped there) read 135-140.  Cyl. 2 reads 120.  The oil isn't foamy, but seems thin and stains the white towel with a greenish-gray tint.  Good spark at all plugs and fuel at injectors.  Exhaust seems 'moist'.

[twistedtree]

2 is low, but I'd expect it to still fire at 120 PSI.  How did the plugs look on the dead cylinders?

[duffelpud]

They looked and felt a bit greasy/oily.  Interestingly, cyl. 4 was getting compression up around 135/140 along with spark and fuel to the injector.

[ja17]

Good time to invest in a new set of spark plugs.  Your Italian tune up may have dislodged some carbon and sent it to a spark plug. Even if your plugs are new, get a fresh set of NGKs and save the old ones for spares. Spark plugs are a cheap place to start!

[duffelpud]

Pulled all six plugs this evening and replaced them with new NGK's.  Everything is back to normal now.  Good call! 

Now on to debugging the idle and lean/rich issues.  Any pointers on past threads that can guide me through the process?  I'm thinking I read somewhere to start with the timing, then fuel flow, then a laundry list of other items including the butterfly valve stop screw, linkage lengths, injection pump sensors and the like.  I need a clear, step by step guide.

[twistedtree]

OK, this looks like a good opportunity to road-test a Tech Manual contribution I've been working on.  This is a first draft - barely more than an outline - but I encourage feedback.  It's an attempt to organize and summarize what I've learned from this site in getting three cars running and tuned (mostly).

There are notes for me to insert links to other articles, but they are not active you you will have to go find those articles (like the Linkage Tour) in the Tech Manual.

Draft begins here:

Top to Bottom W113 Tune Up

This “tour” outlines the steps to systematically work through all the adjustments on a W113 to get it running properly.  The order of the steps is important as many adjustments are dependent on and changed by adjustments made in previous steps.  Since in many cases changing one thing also changes another, if you go about them in the wrong order you can waste a lot of time chasing in circles.

Embarking on these adjustments requires that the car at least starts and runs.  If it doesn’t, you will have to figure that out first.  These steps may provide clues, but it’s not intended as a step-by-step “how to get my car running”.

•   Check compression (is this better done with a warm engine?)
•   Check and adjust throttle linkages.  Don’t assume they are correct.  Over the 40 years your car has been around, chances are someone incorrectly made adjustments that you now need to correct. (Link to Linkage Tour).
  o   If an automatic, confirm operation of the throttle body switch
•   Check cold start devices when engine is cold (link to Starting Aids)
  o   Confirm that the Cold Start Valve (CSV) works properly.  It should squirt fuel for a second or two when the ignition is activated, and with the wires disconnected and the ignition on, it should not leak or drip.
  o   Check cold start solenoid on FIP?
  o   Check time and temp switch states with volt meter and/or test lamp
•   Check Fuel system
  o   Check fuel pressure.
  o   Check fuel flow rate
  o   Check FIP solenoids (start and shutoff)?
  o   Replace fuel filter
•   Replace air filter
•   Ignition (Link to distributor section)
  o   Replace points, condenser, cap, rotor, and plugs.  They are cheap and will eliminate a lot of possible problems.
  o   Check the points’ gap and dwell.  Changes to dwell will subsequently change timing, so this needs to be done before setting timing.
  o   Check resistance of coil and resistor to be sure they are matched?
  o   Check resistance of plug wires to be sure they are matched to coil?
•   Setup to monitor and check warm up process.
  o   Remove FIP Warm Running Device (WRD) air filter (link to FIP section).  Find something to reach down and cover intake hole.  A metal ruler or paint scraper will work.  You will need to cover the intake at various times while the engine is warming up.
  o   Rig a test lamp or volt meter to check operation of time/temp switches.
  o   Connect a vacuum gauge.
•   Start engine and monitor warm-up process.
  o   Check immediately after starting
•   Check for suction at WRD intake.  There should be strong vacuum at the port.
•   Check for proper vacuum on gauge (what should it look like during warm up?)
•   Engine RPM should be 1100?  Note RPM if different.
  o   As engine warms up
•   Temp/time switch should change state at what temp and what time?
•   RPM should slowly come down, and reach 700-800 by around 150-160 F.  At that point, there should be little to no vacuum at WRD intake port.
•   Misc checks
  o   Confirm stable, correct vacuum (value?)
•   Ignition
  o   Confirm dwell reading
  o   Confirm timing.  Check at Idle, 1500, 2000, 3000 RPM.  Timing should be stable, not wondering around.  If not, you might have a worn distributor.
  o   Confirm vacuum advance/retard is working correctly.
•   Idle mixture adjustment (only after engine if fully warmed up)
  o   Adjust mixture using air bypass screw on intake manifold
  o   Verify mixture using split linkage test
  o   If Idle speed to too high/low, adjust (link to )
•   Full range mixture check/adjust (this is more complicated)
•   Confirm operation of dash pots (which ones, and where are they?)
•   Confirm operation of Idle Speed compensator (automatics and/or AC equipped cars)
•   Automatics
  o   Confirm operation and adjustment of shift controls (link to Auto trans section)

[ja17]

Very nice logical start twistedtree.  It looks like you have put a lot of time and effort into the outline.

Some basic comments.........

The CSV will operate only at certain temperature ranges during starting. It varies from year to year and model to model. I have some good descriptions and graphs in my starting aid tour. You can find your particular version there.

The "Cold Start Solenoid"(CSS) on the IP activates anytime the starter is activated, however it was eliminated altogether on latest versions.  

The coil and ballast resistor should be checked and should be matched to each other. Most coils spec which ballast resistor is to be used and the spec. may be shown on the bottom of the coil. Be sure to use std. ignition coils with standard ignitions and transistorized coils with the transistorized ignitions. Be aware that later M130 engines used a factory transistorized ignition. The spark box for these transistorized units is mounted in a very hazardous location (directly under the battery). A leaky battery will take its toll on it.

The spark plug wire have a certain resistance. Check them to see if they are all close. Since they will not all fail at the same time, you will see if one or more is below specs. 13,000 ohms is max resitance from coil all the way through the spark plugs.  The rotor is 5K, plug wires at the spark plugs are either 5k (resistor style) or 1k (non resistor), the plug wires at the distributor can have a 1K resistor,  the coil wire may have 1K at each end. As you can see resistance adds up fast. Some considerations are .....replacement coil set ups, electronic ignitions, can produce higher voltages than original set-ups so more resistance can be tolerated. In any case when the total resistance starts going over 15k you should replace some parts. Usually the resistor at the spark plug end of the wire goes bad first. So figure that you may have 5k spark plug wire ends at the plugs, 5K resistor spark plugs, 5K at the rotor, 1K and 1K at the coil wire. That adds up to 17K !!! Get rid of the resistor plugs and you go back to 12K. If you are using the 5K spark plug ends you can switch to the 1K if you like, that will make the total 8K which is a very comfortable margin.

More to follow.........

Thanks!

Joe Alexander
Blacklick, Ohio

[twistedtree]

Thanks Joe, that's exactly the kind of feedback I need.  My thinking is to reference existing sections of the tech manual as much as possible to cover details for each part of the process.  As you know, much of the detail is already covered really well, but some could benefit from beefing up a bit.  What I found missing as a newby trying to get through this for the first time was the overview that tied all the parts together into a sensible sequence.  And you can waste a lot of time if you do thinks in the wrong order.  For example, setting idle mixture and speed, only to find later that the WRD is not closing all the way.  Fixing the WRD will trash all the idle adjustments and force you to re-do them.  The same goes for just about anything if you haven't got the throttle linkages set up properly.

[ja17]

The first thing I do before a major tune is, while the engine is hot, I loosen the radiator cap and retorque the head bolts, after the engine cools, I then adjust the valves. If a compression check is to be taken, it could be done first on the hot engine. Leave the plugs out so turning the engine for the valve adjustment can be done easier.

[twistedtree]

A valve adjustment - now that was a glaring omission.  I'll add it in.

[Naj ✝︎]

And clyinder head retorque prior to that?

Naj

[twistedtree]

Can I solicit a few volunteers to be part of a review team?  Joe?  Naj?  Others?  Then we can work it off-line via email, etc.

[Naj ✝︎]

PM sent

Naj