Engine running terribly (too rich)

[Miloslav Maun]

Please help me with some good advice, I am starting to be desperate. I have a problem with my second pagoda which I can't solve since two months.

I can't make the engine run smoothly. I did almost everything that came to my mind but still no luck.

The car sat for a long time (15Y) and according to the previous owner it ran fine before.

Now it runs very badly. The idle is not perfect but at least it is constant. Without load the engines revs up ok (but could be better). The problem is acceleration under load. The engine seems not to have enough power, it goes into revolutions with hesitation and "chuckling" or "bubbling" sound. Taking the foot off the gas pedal results in slight backfiring sometimes.

The spark plugs are sooty black (only in about 2 km ride they are not firing well anymore and the ride gets even worse).

What did I try:
Change the spark plugs (twice, NGK, Champion - the original old champions seem to work best)
Exchange the ignition wires with my other pagoda, which runs fine - no noticeable difference
Change the injectors (got brand new ones but no noticeable change so I think I'll put the originals back)
Valves adjusted
Timing advance
All the linkage is set correctly
New Air filter, new engine oil
The distributor seems to be new (replaced before those 15Y of standing) - I have inspected it for any sign of wear or light in a dark garage - no light leaking anywhere
Coil also changed not long before

I have tried to adjust the idle screw on the back of the injection pump - turned it even 30 clicks CCW without any noticeable change - spark plugs still black and sooty.
The engine has a weaker compression (8 to 9). I ran for about 100 km and it consumed half of the tank. BTW: The fuel feeding pump was dirty with fuel residues - I have opened it, changed all the seals and cleaned the dirt. It seems to be working fine - the fuel flow is strong and constant. I also cleaned the filter mesh in the pump (the tank filter is non existant and the inside of the tank is a mess - I shaked out lots of sand and debris).

I ran out of ideas. If anybody has some hint, please tell me.

[Peter van Es]

Have you done a search on the forum? Use the Search box and search for "Running Rich"  and then check those threads...

Peter

[Miloslav Maun]

Yes, I have searched the forum, now I have about five browser panels open with different threads but unfortunatelly I was not able to find the right answer yet  :'(

This forum is a great help to me. All I did so far with the engine was based on the information gained from the forum.

[menesesjesse]

Muf
There could be several culprits but I would check the cheapest first.  Make sure all the vacume hoses are intact and not cracked.  I would then check the CSV for major leakage and then I would move towards the injection pump and fuel lines.  Make sure the return line is not restricted. Hope this helps a little.
Jesse

[Miloslav Maun]

menesesjesse,

I have inspected the fuel lines from the pump to the injectors. They are through (I tried to blow with my mouth). Unfortunatelly I did not manage to clean them with a wire (the wire I had was too hard and did not go all the way through). I do not know how easy it should be to blow, I kind of expected less resistance - but they were all about the same and all through. And there is petrol going through, if the car runs, isn't it?

The vacuum hose to the brake booster is not perfect but can this result in such richness and misfiring? Anyway, the other hose from the valve cover seems to be ok. Are there any other vaccum hoses? All the rest is water, is it not?

I fear for the worst - the injection pump.

[ja17]

Hello,

It sounds like the classic symptoms of a stuck warm running device "WRD".  If it stuck when the car was stored 15 years ago, it will be extremely rich running. Make this your next item to check.  A simple search should bring up lots of info.  If not let us know and we will talk you through it!  Good Luck!

[230slhouston]

Muf,
I also woke up my 230sl after 20 years. Besides doing the normal items like cleaning the tank, changing fluids, renew fuel lines etc, I went through 3 sets of spark plugs and did not even drive 5 miles. I did not even drive out of my garage and had to change it once. On Joe's advice and other member input I realised even a new set of plugs can foul and fool you.

My symptoms were, it started right up with the fresh plugs, idles fine, burnt rich. Idle was fine, it dropped, lost power and disappointed me. On my third set of spark plugs, drove a couple of miles, every time slowly increasing speed and gaining confidence. One more thing I did was remove the breather pipe from the valve cover and fed it into a bottle just in case it was fouling the plugs.

After 50 miles, I could start hearing and feeling the difference. Everyday was a new awakening, I now can cruise at 80MPH, engine sounds great (uses a little oil though). Over the last year I have proudly done 2000 miles.

I also took out the IP and freed up a plunger that was stuck in position.

Subsequently, I did tinker with the adjustments and WRD, added shims etc. My car is not perfect but good enough for me.

Cheers and good luck
Maistran

[Benz Dr.]

The WRD can be free and still the car will run very rich. The CSV can be leak free and it will still run rich. The IP might be working properly, and the ignition is OK, yet the plugs foul out so you won't really know that some things are working until you find this simple problem.

 The inside of the small cyinder that holds the thermostat for the injection pump you need a constant flow of coolant. As the temperature rises from a cold engine the hot coolant will make the wax type thermostat move the slide valve and also the rack inside of the pump to the full lean position. Well, if the housing is plugged no coolant can flow around the thermostat and it won't move. PLace your hand on or near the thermostat housing once the engine comes up to temp. If it's working it will be very hot. If it's not working it will be cold or just a bit warm and you should be able to hold on to it. I found this problem on the 300SE I've been working and once I got it cleaned out it was a whole different engine. It was really plugged with stuff that looked like old dried up mud.

If it's not working take it apart and clean it out. You will find that the engine will slow down once it gets warm and it might even stall. That's OK, it's lean now. You will have to reset your pump at idle and do a few adjustments to get it running.
If it won't run right after that you have some other problem and you will need to go back through and look for smaller things. I attack each part of the system one piece at a time and fix everything as I go. Once I've done that then I look at how the complete system is working and adjust individual units until I dial it in.

Idle speed is a comprimise between ignition timing, air, and injection pump idle adjustment. Move any one of them and it affects the other two.

[glenn]

Muf, I think the 'Group' should plan a PPP - Prague Pagoda Passage for diagnostic actions  and PPP - Pleasant Pilsen Potions (no driving).

    Also, 8 miles to the gallon???   This usage has its own symptoms  Smoke?  Leaks? 
.

[Miloslav Maun]

So... Today I spent the whole day working on the warm up regulator. I have checked the thermostat (I have the long brass type - early?). I tested it in boiling water and the pin seems to be working fine. It has extended by some 4-5 mm.
It was sealed in the housing by some silicone, so I sealed it the same way when reinstalling.
The WUR base with the air filter seems to be working fine. Actually, I can't imagine what could get stuck here.
I also checked the thermostat housing for temperature, as Benz Dr. sugested, and itgets really hot, I cannot hold my finger on it.

But the spark plugs are still becoming sooty. Interesting is that cylinder nr. 2 is not. Strange. (But I cannot guarantee that the cylinder gets fuel after all... )

[Miloslav Maun]

I have made a test: disconnected the rod to the injection pump and pushed the gas pedal (i.e. added air with no extra fuel). The car goes up in revolutions like before. Is it normal? I think not.
In the same time I've disconnected and plugged the auxilary fuel supply to the intake manifold to be sure no fuel is going through here.

The WRD seems to be working - the pin is out when the water is warm. BTW Do those barometric regulators ever go wrong?

Two days ago I've removed the starting solenoid to see what is inside. It seems that the lever in the pump (that the solenoid is supposed to move when starting) is not linked to anything and has no function. Maybe I am just wrong but it seems to me as if the "rack" was way too in the front all the time. I tried to move it backwards with my finger but it always returned back (to the front).

Any suggestions? Should I start diassembling the pump?

PLEASE HELP - I am going to disassemble the pump tomorrow

[Largeowner]

MUF,

On the 230 SL's the IP has a closed oil system...It does NOT get oil from the engine!  Chances are the IP oil is 15 years old and pretty mucky!

I use a cheapo hand suction pump with an attached 4 oz cup to suction out the old oil (4 oz at a time).  I took out and replaced 12 oz last time I changed it.  You will probably need to run it for a while with the new oil, and change the oil again.

Fixed my "runablilty" issues right away!

Large

[Ulf]

Had a similar problem an tried the same things as you have, finally it turned out that my timing chain was 14 degrees off - a replacement and following valve adjustment cured that and now the car doesn't use as much fuel as before.

Ulf

[Miloslav Maun]

I owe you the solution of the problem. The main control rack was stuck after all those years of sitting. It did not move and control the amount of fuel so the pump delivered maximum all the time. The trouble was solved by removing the screw on the front part of the pump. Then we used a size 5 screw and screwed it on the end of the rack. Then we moved it back and forth till it was loose enough.

[Cees Klumper]

Congratulations on solving this problem Muf ...