confusing- engine running bad

[Basil]

My 230 SL 1964 is running very well when cold. After 2 miles or so, when the engine heats up, it runs very bad. Lack of power misfiring etc. The "engine starting aid" in the Technical manual mentiones that relais I is responsible for activating the solenoid on the injection pump. Underneath that line is a diagram that tells that relais II is responsible.
When i got the car the relais of the cold start was down. It ran very bad with a for to rich mixture. Black sparkplugs. In a garage, they fixed the mixture to the right CO content.
After that, the car drove much better. Back home I changed the relais for a new one . After that , when cold, running very well, when warm very poor.
Sparkplugs are white .
Can anybody help me on the way ?
Paul.

[garymand]

Yes confusing.  It was running good? All you did was remove a bad relay and replace with a good relay?  Which relay is it?  Maybe the Cold Start relay?  It opens the Cold Start Valve?  If the CSV is leaking or on all the time, it will be very rich and run very poor. 

W113 has a 'split throttle linkage'  disconnect the shaft to the FIP.  Push the shaft down for richer, open the air butterfly for more air: see if too much gas for sure.  If too much gas AND the relay did it 1) put the bad relay back in
2) find where the gas is coming from.  Sounds like your CSV is leaking (not stopping the extra gas when it should.)

[GGR]

Looks like you had a fault that wasn't corrected and adjustments were made for the car to run with that fault. When you corrected the fault the tuning was now off. What did the garage do to correct the CO? Did they act on the injection pump main rack? Ask them precisely what they did, this may help us understand better.

[Basil]

@Garymand: Is the CSV opened untill the engine is warm ? I thought from reading the manual, that the small round timing relais allows opening for only a second.

@GGR: This morning I checked the CO myself. 8,9.  So the garage did NOT corrected the percentage. With engine shut off I clicked 9 points to the left untill it was at 3,1.
Engine was running better when warm, but not optima forma.
I called the garage to ask what they had done. Answer was only a lot of bla bla. (not my garage).
I let the engine cool down and started it to let let it run on idle.(not driving). Sounds good and after a few minutes, rpm goes down , doesn't run well and even shuts down by his own.

     

[Basil]

Of coarse, it might be, that the adjustment on the FIP was right, but that the high CO value comes from a leaking CSV

[GGR]

That adjustment you mention is only richness at idle, it does not influence richness over the whole rpm range. Do not touch that adjustment while engine is running, or you will damage it.

I think you should diagnose precisely and methodically what's wrong rather than modifying adjustments that will be all be off once you find the fault. People here will help you. If I were you I would start by making sure the ignition it right (advance, condition of points etc.). Then I would do the linkage tour. Once you're sure all that is in order you can then narrow down item by item.

[garymand]

The FIP has a cold start solinoid that is only on while starting.  It is controlled through a relay.  The CSV controlled by a relay and is held open by the Thermo Time Switch until the engine warms.  There is a small inspection screw on the CSV to see if it is leaking with no voltage to it.  The CSV brass needle and seat age and leak, allowing gas to continue once the engine warms but the supply voltage is gone from the CSV.  Carefully remove the little bolt, don't loose it.  With a cold start and the voltage on the CSV, gas leaks out the hole.  With a warm engine (I'm forgetful here, but I think the CSV is not activated on starting) no voltage (use a meter or just remove the wire with the motor warm) You should see no gas leaking at all.  I had a bad CSV, I tried to reseat the needle but gave up, I couldn't stop the leaking -R&R CSV fixed it.  

Its nice you have a CO meter.  "With engine shut off I clicked 9 points to the left" must be the idle screw on the FIP.  That was a lot rich, but you need to make sure your fix was fixing the right thing.  Doesn't sound like you have found the problem yet.

[Cees Klumper]

Any possibility you have contamination in the fuel tank / system? Rough running after a while is oftentimes caused by debris in the tank that gets unsettled and plugs things up  when the car starts to move; then settles back down after the car has sat for a while.

[Basil]

Thank you for your quick answers.
I will adjust back to the startingpoint and go from there , checking ignition , csv etc.

Once I turn on ignition, I hear and feel the fuelpump running. It keeps on filling the fuel filter for quite a while. Is there a fuel return to the tank ?
Is there besides this big filter on the engine another filter ?

[garymand]

Good, the pump runs all the time, recirculating fuel through the whole system.  there are screens and a nice big filter.  What Cees is getting at is the engine stalls when the filter plugs with rust. The pump keeps running but the filter is plugged so the engine dies.  In a few minutes the rust falls off the filter and the car can start and run until the aggitated rust covers the filter again.  It doesn't sound like your problem.  Follow GGR's advice and start fresh at the linkage tour, then test the csv and Warmup device for gas and air on the FIP.  These all need to be working right.  The other solenoids only activate at starting and you say it sarts fine, its after it warms you have the problem. 

[Basil]

Cees, fuel filter is clean, no debris at bottom of the housing.
CO setting for idle back to what it was.
Now able to set idle at the airscrew.
Set idle up to 1100
CO at 1100 6,2
         2500 0,26
         3500 5,4

Poor CO at 2500 and I got the feeling the engine is missing power, hickups and backfires in that rpm range when driving.
I will check that tomorrow.

Enough food for thought ?

[enochbell]

This is a long shot, but I had warm running issues that baffled me for the longest time.  I went through everything, testing and adjusting until I was out of ideas.  Finally took it to an indie (first time in the shop in 14 years) and he diagnosed the problem just by listening.  Bad spark plug wires.  Replaced them and problem solved.

Good luck,
g

[ja17]

An experienced ear is hard to beat.  At least you have everything else checked out now also!

The Pagoda Golden Rule..........  "Before altering the expensive and complex injection system, make sure you have a perfectly tuned engine, a tested WRD, a leak proof starting valve, correct engine linkage, and a clean fuel supply with adequate pressure and volume".

I guess ignition wires fall under "perfectly tuned engine" .

[Basil]

Circuit breaker points hardly opened :'(

Engine runs much better now, but is still missing between 2000 and 3000 rpm where CO is 0,24

With more than 3000 rpm it picks up well.
What could be the cause of low CO in that rpm range

Now we have a tested WRD, a leak proof starting valve, correct engine linkage, and a clean fuel supply with adequate pressure and volume".

[GGR]

It is difficult to measure CO other than at idle. A well tuned engine should have its CO as close as possible to 0 under load, but you need to embark the CO meter in the car while driving.

Always have ignition sorted first, as otherwise all else you alter will be off when you put the ignition right. So you made sure your points are now opening correctly. Did you check advance at idle and at 3000 rpm as per workshop manual? Then check spark plugs and HT wires. You should measure resistance through all of them and they should all be the same.

You say your linkages are now OK. did you follow all the steps of the linkage tour? This may be something your garage has altered. Also a common mistake is to "tune" idle at the throttle body instead of the idle screw. Make sure your TB closes properly, but I think this is described in the linkage tour.

[Basil]

All the leads have the same resistance 2k Ohm  1 for the lead, 1 for the cap.  1 cap has 11 k Ohm.
I measured different caps, but everey brand seems to have its own resistance . Champion has 4 k Ohm
Better to renew all the caps , no matter what the new resistance is, as long as they are the same ?

Paul.

[GGR]

I don't have the figure with me, but it should be rather low resistence. Look into the workshop manual if you have access to one. Spark plugs should also be non resistance ones. Try to get as close as factory standards. Usually increased resistence happens on the lead towards the spark plug. If all your leads have the same resistence try to replace the faulty cap by a used one which has same resistence as others and see if it improve things.

[ctaylor738]

11K is definitely high, and that cap should be replaced.  The book says not more than 16k ohms resistance from the coil through the spark plug.  There is probably 5K in the rotor, 1k in the coil wire.  If you have 2k on the wire and cap, that's 8k, so you should be OK with another 5k in the spark plug.

[garymand]

Still confused.  I didn't know the cap has a resistor built in, funny, I've never tried to measure cap resistance.  There is a spring-loaded carbon brush inside at the center.  It contacts the rotor.  I would ASSUME it would measure no more that 1 or 2k ohm.  11k through the cap is strange and suspect to me.  Are you measuring just through the cap or through the cap to ground.  That might explain the 11K.  The secondary of the coil is at least 8k.  If you measure from grund to a plug wire socket on the cap with the cap in place on the distributor AND the coil wire in place, yes you should get 10k to 20K depending on your coil and the integrity of the connections between.

There is a resistor built into the rotor, 1 or 2k I think, and no resistance in the wires, The wires are stranded copper, there is a 1k resistor built into the plug boots so the plugs are not resistance plugs.  If you have resistance wires, the boots should not have the built in resistance.  Careful what you measure and make sure your measurements are repeatable. 

"The book says not more than 16k ohms resistance from the coil through the spark plug."  That measurement should be from ground to the center electrode of the sparkplug.  That would be measuring ALL the resistance including bad connections, from the coil ground at the chassis to the very tip of the plug.  Funny, I've never measured that either. 

[Basil]

Did not have early sparkplug caps have much resistance because of lower interference with the radio ?
Resistance was measured through the cap.
I put in one with zero res. but that doesn't help.

[ctaylor738]

By "cap" I am assuming that Basil means the "boots" on the plug end of the wire, not the distributor cap. 

There is 5k in every rotor that I've measured. 

Some coil wires may have 1k.

All of the plug wires both early and late are supposed to be 1k according to the respective BBBs.  But the early cars are supposed to have 5k spark plugs. "Spark plugs with suppressors (5 k ohms)" See page 82-20/1.

[garymand]

So what do you call the rotor cap? and what was measuring 11K

[Basil]

Boots are made for walking and that's just what I will do, if I don't solve this little problem.

11 KOhm was measured in one of the 6 sparkplugboots
1 KOhm was in the wire from the distributorcap to the boot

[garymand]

What?  11k on one boot, what did the other 5 measure?  Unscrew the boot from the wire.  Look close at the wire, I think it is stranded.  The screw inside the boot connects to the wire by screwing into the end of the wire. 

[garymand]

MB uses stranded wire core wires not resistive core wires.  at each end of the wire is a resistor.  If you have resistance wire, you do not need the resistors at each end.  I don't have my meter with me or Id test mine now.  I'll check when I get home, but I'm 90% sure the wires should be stranded copper core, non-resistive wires.  Each boot should measure the same 1K give or take a few hundred.  None should be higher than 2K.  If youhave one at 11 you found a problem.