Ignition playing up

[karmannghia60]

This is on the wife's '69 280SL. I adjust the dwell angle to 40 as recommended in the handbook. Runs like a dream for awhile then it loses all power and runs like a dog. Most likely when gets hot but not everytime. Last time it did that, I checked the angle and it changed from 40 to 27. I took it to the mechanic who set it to 40 again and confirmed timing was spot on. I drove more than 350klms last weekend with no problems then it played up again today. It stalled and wouldn't start then after a while no probs. I am going to replace the points AGAIN and condenser as well. Would it be the condenser or the coil or something else? The points themselves don't seem to have moved at all.
help please

[Cees Klumper]

It's worthwile to check the resistance in the spark plug wires & caps. Two years ago a faulty wire caused similar symptoms to yours, and the wire set was only two years old then. Do you have the emission controls?

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[bayleif]

Raf,
I second Cees' suggestion. In addition, make sure you have the correct electrical components, coil, ballast resistor/s etc. for your car. As I remember, 1969 was when they broke in the electronic ignition. My car, also a 69 did not have the electronic ignition but someone along the way installed the coil and ballast resisters that were supposed to go with the electronic ignition. The result was that I also had intermittent problems which seemed to be temperature related.

Chuck Bartlett
1969 Signal Red 4 Speed

[karmannghia60]

OK, I replaced the condensor and points. Angle stayed at 40 but car still played up big time today. I disconnected the plug leads one by one while the engine is running, revs dropped with each of them and I can hear the spark between the end of the lead and the plug. When warm and I accelerator hard, it would misfire bady and stays running rough afterwards. Could it be the dizzy vacuum advance stuffed? So it would misfire badly at acceleration then stays bad for a while?
Thanks for the advice
Raf

[Malc]

Sounds silly but if you get the same problem, open the bonnet when it's dark and see if you see any arcing from the plug leads, coil or distributor cap.

Is the rotor arm ok??

Make sure that the engine earth (ground) is in good condition

THe advance could be sticky, especially the weights. I have not dived into my 230 yet However if it's a Bosch distributor like the one on my BMW 2002 you must put a drop of oil under the rotor arm every 3000 miles or so otherwise they will start to seize and display the symptoms you have. I actually had to build one good distributor out of three
HTH
malc
Scotland

[George Davis]

Pull the rotor off and try to move the end of the shaft side to side.  If it moves perceptibly, there is wear in the shaft or bushings that will cause the points to degrade rapidly.  Rebuilding any 40 +/- year old distributor is probably worthwhile.

George Davis
'69 280 SL Euro manual

[ja17]

Hello,
Sounds like your car rus great while the points are correctly adjusted. Be sure to grease the cam on the distributor when replacing points. Also original equipment Bosch points seem to last longer and work beter than any others. There may be an exception or two, but you cant go wrong with the Bosch points. As Cees recommends, use an ohm meter to check the spark plug and coil wires.

One other thing which can fail after running hot is the coil.
If you get some numbers off your distributor, coil and ballast resistors we may be able to check some things. What is the history of this problem?

Joe Alexander
Blacklick, Ohio

[ja17]

Hello again,
You may have a fuel starvation problem. Do a volume and pressure check, then read fuel tank tour.

Joe Alexander
Blacklick, Ohio

[karmannghia60]

Its definitely happening when the car is warm. Stalled in the middle of the hwy twice today and wouldn't start. I had to leave it to cool down for 1/2hr or so then it will start ok and runs for a while. Yeah, checked the rotor and shaft OK. I think I will replace the coil next and see what's the go
Raf

[ja17]

Hello,
Find out whether it is fuel or ignition first.
Try a test drive with a full fuel tank, or check the fuel return line to the tank for blockage. A fuel pressure check will  show too high a reading if the fuel return line is blocked!
The ignition could still have q problem (coil) or the factory transistorized ignition  (if your car is equiped) could be acting up. Just check to see if you are still getting spark to the plugs when it is acting up.
Start with the inexpensive things first. Replace the main fuel filter if it has not been done recently. Take a fuel pressure and volume reading. Check for spark, when the car acts up, Try a temporary ignition coil. Keep us up to date! Good luck.

Joe Alexander
Blacklick, Ohio

[karmannghia60]

Thanks for all the advice. I put a new coil in it this morning as well as coil/distributor lead. Seem to be running ok although I need to take it for a longer drive to be sure. Will keep you up to date
Raf

[karmannghia60]

Good news and bad news. The coil didn't make a difference played up again this morning after being stuck in traffic for 15 minutes. The mechanic reckons it was just the spark plugs. So will give it a try tomorrow.
This is the good news, the bad news now I have a steering problem. When it stalled last week, I had to push it and steer it while the engine was off. Now I have a sizeable (scary) amount of steering free play. Is there some kid of a rubber cupling between the steering wheel and the box somewhere that could have hosed itself?
Thanks again
Raf

[n/a]

This is more of a question on this subject.  Could the above problems be replicated in the shop by running the car at idle say for 2-3 hours reving the engine once in a while?  That way you could trouble-shoot in the shop and not on the hwy somewhere - please correct me if I am making wrong assumptions somewhere.  Having this would really help my situation out and maybe even Raf's.

Workineh Yemesgen
1952 Chevy Styleline
1954 BMW 502 V8 Ex-Haile Selassie
1957 Mercedes 190 Ponton
1957 Mercedes 220 Ponton
1961 Mercedes 180c Ponton
1964 Mercedes 220SE Fintail
1965 Mercedes 230 SL
2003 Mercedes G 270

[hands_aus]

Raf,
You say your problem happens when sitting in traffic.
Normally the system uses the flow of fuel to cool the injection pump and all the components of the fuel system.
If the "return" fuel line is blocked the fuel sits in the fuel lines and can boil causing air bubbles in the injection system.

This will cause problems with the way the engine runs.

You can check the return fuel flow by removing the hose from the return line that connects to the fuel tank and put that hose into a container and measure the amount of fuel delivered in 15 seconds.

The correct fuel flow will deliver 1 litre.

Also make sure that the return inlet to the fuel tank is not blocked.

I also suggest you do a search for the Topic "FUEL TANK TOUR". You will be able to see what the inside of the tank looks like and it will help you identify the correct hose connection.

There is a flexible coupling between the steering wheel and the steering box.

Do another search on the forum here and you should find lots of info about this problem.

Bob (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[karmannghia60]

Same crap this morning again. Called the mechanic, he is telling me I must have some water in fuel. He's recommending I put a bottle of metholated spirits with a full tank of petrol. Anyone has done this before? I am a bit reluctant

[graphic66]

I use "dry gas" in my fuel in the winter to help with moisture in the fuel. Use only the isopropanal 99% alcohol version and not the methanol type. You can also buy the alcohol at the pharmacy, just make sure it is 99% pure. Add about 8 ounces to your full tank and see if it helps. A little bit of water can go a long way in an engine. The alcohol may help but if you have a lot of water in your tank you may need to remove and flush it and ckeck for rust. Always when storing your car add the proper fuel stabilizer to your fuel to avoid this and other fuel problems. Stabilizer stabilizes the fuel and acts like dry gas to help any water accumulated from condensation pass through your system. Always store with a full tank also to avoid condensation.

[J. Huber]

Hi Raf.

I would take to heart the previous suggestions about fuel delivery as the culprit. It is essential that the lines are clear and the fuel is circulating (especially when the car has warmed up). Have you tested it yet? Have you checked all the fuel filters? Benz Dr and others have commented a lot on how debris and air pockets can cause warm-running issues. Try a keyword search. Good Luck.

James
63 230SL

[Cees Klumper]

Also, with the engine warm, it would be useful to check the functioning of the ignition with a timing light, at the various engine RPM's. If the distributor, points, plugs, coil etc are functioning ok while the engine is nonetheless running poorly, then it would have to be the fuel supply?

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[blairwag]

I'll bet you have a combination of problems. From my reading, you definitely have a temperature dependent problem. They fact you got stranded on the roadside - left the card to 1+ hours to cool - then it started and ran fine is a HUGE clue.

What does your engine temp guage read when it runs good and when it runs bad?

There are (atleast) 2 temp sending units on the engine. One up by the thermostat housing, the other on the block, behind the fuel injection pump. I'd start by testing them both for proper operation (or blindly replacing them). Then I'd check those 4 relays all for proper operation. There are actually 5 relay like things to test / work on: the 4 mounted on the driver side fender under the bonnet (US model cars), and the shutoff mounted to the rear of the fuel injector pump. I HAVE TO BELIEVE that something is malfunctioning in this arena. Use the test procedures outlined in the BBB to test these.

Once you have isolated and resolved any issue with these, I believe the symptoms that remain will be more indicative of the other half of your problem --- as others said, likely fuel supply.

...I doubt your problem is water in the fuel - because there's no way that letting the stalled engine cool for 2 hours would resolve water in the fuel and allow the car to start and run well. I suspect a delivery problem - maybe something as simple as a clogged fuel filter, or something.

Remember, the speed relay works closely with the other relays and talks to the distributor for vacuum retard (or advance - depending on the model), and it talks to the intake manifold (in the form of vacuum pull). These relays are covered in the engine emissions section of the BBB - and can have a HUGE impact on engine performance.

good luck, and keep us posted.


--
~~~~~~~~~~~~~~~~~~~~~~~~~~~
William Blair Wagner: blairwag@earthlink.net
Education is not always knowing the answer,
...but rather knowing where to look for it!
1971 280SL US Automatic
~~~~~~~~~~~~~~~~~~~~~~~~~~~

[karmannghia60]

Hi All, just an update. The problem seem to have gone away after replacing the plugs and putting some metho in the tank. So I am not quite sure which fixed the problem.
Thanks for all the advice

[Malc]

quote:Originally posted by karmannghia60

Hi All, just an update. The problem seem to have gone away after replacing the plugs and putting some metho in the tank. So I am not quite sure which fixed the problem.
Thanks for all the advice

If it appears again you might want to concider change the spark plug leads, they do break down after a couple of years
Malc