Author Topic: engine runs rough when warm between 2k -3k Rpm???????  (Read 13171 times)

olaf

  • Guest
engine runs rough when warm between 2k -3k Rpm???????
« on: February 11, 2009, 02:35:23 »
I am a new proud owner of a 1970 280SL and want to get everything running perfect.
just recently added the pertronix ignition and was hoping it would solve my problem but it did not.
when cold, the car runs good. as soon as it warms up it starts jerking and hesitating at low RPM.
Can anyone help me with some tips here.
also i wish to adjust the valves, does anyone know the cold clearance recommended for exhaust and intake?

Thanks for a very informative website.
Olaf


jeffc280sl

  • Guest
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #1 on: February 11, 2009, 03:21:43 »
Welcome to the W113 site.  I hope you enjoy your new car. 

The FIP or fuel injection pump has a thermostat that helps to enrich the fuel supply to the engine much like a choke.  There is also a TTS or thermo time switch used as a starting aid.
There are many discussions on this site addressing the function and operation of the CSV or cold start valve.  It is a fuel enrichment device that helps the initial start a cold engine.  These devices sometimes break or work intermittantly.  Do a search on "FIP thermostat", "TTS" and "CSV" to learn more about the devices.   

I would focus on the FIP thermostat first.  There is a filter that you can remove o determine if it is operating correctly as the engine warms.  Read up do some tests and give us some feedback.  Most of us have been where you are and are eager to help.

There is a great write up on adjusting valves at the following:
http://www.sl113.org/forums/index.php?topic=10218.0

If you can't access it via the link search for "adjusting valves".  Again there is a wealth of information on this site.


Peter van Es

  • Honorary Member
  • Platinum
  • ******
  • Netherlands, North Holland, Nederhorst Den Berg
  • Posts: 4070
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #2 on: February 11, 2009, 08:22:11 »
If you are a Full Member you can access the Starting Aid Tour, which explains how all these thermostats work together and can be adjusted.

http://www.sl113.org/wiki/pmwiki.php?n=Restricted.Engine-starting-aid-tour

Much of the content is also here: http://www.sl113.org/forums/index.php?topic=5486 but less well organised and not as detailed.

Peter
1970 280SL. System Admin of the site. Please do not mail or PM me questions on Pagoda's... I'm not likely to know the answer.  Please post on the forum instead!

ja17

  • Full Member
  • Platinum
  • ******
  • USA, OH, Blacklick
  • Posts: 7410
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #3 on: February 12, 2009, 04:20:58 »
Hello,

Sounds like it is running lean when warm.  Start with the inexpensive items first. Make sure the fuel filter is clean.  Then check back for more ideas.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

olaf

  • Guest
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #4 on: February 13, 2009, 02:39:52 »
Thank you all for the great info. I am impressed with all the info that i can find on this site and how
knowledgeable you guys are. I thank you for your understanding and time.

Today I started with the least expensive part. I changed the fuel filter.  I needed a new one so it was a good start.
It did not change anything as far as the engine performance and the missing and rough running when warm.
It feels so good driving it when it is cold so i cant wait to really get it to where i want it.
The last owner of this car told me that the engine had just been rebuilt. I will learn how right or wrong he was when i start digging into it. tomorrow I will do a compression test and I will keep posting my progress to bring this car back to life.

My goal is to change every part, or upgrade every part that can make it run smoother and better. think of it as bringing a car that has been in storage for 20 years back to the new century.
I will look forward to any input you all can give me.

First thing first. I need to get the car running the way it should.
I tried accessing the starting aid tour but my log in name did not work there. I use the same one as here but no.

To make it easier I have added a few pictures of my engine. as you can see i took the warm running device apart to clean.
can this make a difference? how should this device work and how should i test it? as you can see in the picture the little solenoid with the pin inside it has been sealed with silicone as a gasket it seems like. i wonder if this is the correct way to seal it?
I don't have the starter solenoid as you can see in the pictures. on the back of the fuel pump it says rebuilt by bosh, so i assume it was done properly, but most likely a while ago.

any input would be greatly appreciated.

Peter van Es

  • Honorary Member
  • Platinum
  • ******
  • Netherlands, North Holland, Nederhorst Den Berg
  • Posts: 4070
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #5 on: February 13, 2009, 08:35:09 »
I tried accessing the starting aid tour but my log in name did not work there. I use the same one as here but no.

That's because you are not yet a full member... check this out: http://www.sl113.org/index.php/membership.html

Peter
1970 280SL. System Admin of the site. Please do not mail or PM me questions on Pagoda's... I'm not likely to know the answer.  Please post on the forum instead!

graphic66

  • Guest
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #6 on: February 13, 2009, 14:26:56 »
Not sure about a 1970 but my 66' really perked up with non resistor spark plugs. Maybe not your problem but it could be a combination of things. I would definitely get non resistor plugs, I run NGK BP5ES non resistor. Also you plug wires should be 1000 ohm resistance. These two things are many times wrong on these cars. Of course the timing on these cars is very important. How about the timing advance in the distributor, if that is stuck it could cause problems. Open the distributor and apply vacuum to the vacuum line and see if the parts move in the dizzy. Also after a hard run with it missing get right out and pull the spark plugs and see if they show a lean or rich condition. A spark plug that is cold can be a clue as to one that is not firing good, so first feel every plug to see if they are all hot just after shutting down. I am a throwback cromagnum knuckledragger that prefers points to Petronix, so of course I would pull that out and go completely stock first, and see if things improve. I remember a funny saying years ago that the word carburetor was French for " the problem is the ignition". 

olaf

  • Guest
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #7 on: February 13, 2009, 15:51:59 »
Thanks again.
I just paid to become a full member. look forward to that.
I will check spark plugs. can anyone tell me what the correct gap should be on these cars and what spark plugs you guys use.
also, if anyone know of a good vendor that sells plug wires at a reasonable cost.


graphic66

  • Guest
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #8 on: February 13, 2009, 22:07:30 »
NGK BP5ES .034 contac Dan Caron The Benz Dr. about plug wires and ends, He may be able to help. Just make sure you have non resistor plugs. They can be hard to find. Suppliers always want to give me the "r" plugs.

Benz Dr.

  • Vendor
  • Platinum
  • ******
  • Canada, ON, Port Lambton
  • Posts: 7219
  • Benz Dr.
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #9 on: February 14, 2009, 06:51:10 »
The 1970 280SL has a vacuum switch over valve. Vacuum is supposed to go to the distributor up to about 2,2000 RPM and then shut off. Check that and see if it works.

If you have a fuel problem it will slow down quickly and loose power. If you have a timing problem it will tend to hit a certain speed and not want to rev up any higher. Ignition problems tend to cause rough running with spark plugs more of a miss.
 The injection pump will have very eratic running over a wide RPM range. The engine may idle smoothly yet start to sputter as you increase engine speed with the car in neutral. No amount of tuning will change how it runs. After testing fuel volume, plugs, valve timing, ignition wires, points, distributor advance/timing and you find nothing wrong it points more to IP trouble.

As a major part of the car and specifically the engine, the rebuild costs for an IP are not as high as some make them out to be. IP rebuild is less than having the head pulled for a valve job. It's definitely less than an engine rebuild, more than a rad recore, more than the price for a soft top but not installed, depending on where you buy a fuel pump it can be more or about the same price, less than a paint job, less than chrome plating, more than a carpet kit without installation and about the same price as a full set of re pro bumpers.
However, aside from the mechanical things I just listed, it's one of those things you NEED to make your car run. Which makes me wonder why I see all this wailling and gnashing of teeth every time someone is confronted with that prospect. It's a fuel injected car and it has a IP. Try pricing a new fuel distributor or an ECU for a late model MB and you'll think your old car looks better every day.

Anyway I got a bit off topic and you have some things to look at. Let us know what you find.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

olaf

  • Guest
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #10 on: February 15, 2009, 18:17:51 »
Thank you very much.

I took apart the WRD. one question I have regarding this device.
How do I check it?
are there any gaskets in this device? I see one silicone gasket that looks like it was home made and one bottom metal
gasket at the base. Does anyone know how to properly put this back together and then test it.
Also, the little air filter. Is this just a cover or does it actually have a filter inside that needs to be cleaned or can it just be rinsed and cleaned with other cleaner agents?

see picture of what i have so far after taking it apart.

« Last Edit: February 15, 2009, 20:40:59 by olaf »

Mike Hughes

  • Full Member
  • Platinum
  • ******
  • USA, VA, Blue Grass
  • Posts: 1748
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #11 on: February 16, 2009, 23:47:03 »
If the air filter you are talking about is the one that is still attached to the large housing in the upper left-hand corner of your picture, then, yes, it can be replaced - and should be.  This part is available from M-B, either the Classic Center, or through your local dealership parts department.  I ordered one from the M-B dealer across the street and they had it by noon the next day.
- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havana Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

olaf

  • Guest
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #12 on: February 17, 2009, 02:27:22 »
New update
Thanks for all the great info.
I have taken the WRD apart and put it back to gether. it works like it should. was open when i started cold and shut when the engine got warm. Does not seem to leak at all when shut. I put in new NGK bp5es plugs gaped at .34.

The car ran beautifully when cold of course, and then as soon as it got warm it started hesitating and running rough again. just like before.
I drove home and on warm engine checked the compression, it measured 190 on all cylinders. right on.
But the spark plug tips were totally white. So i must be running very lean.

When i took the WRD apart i measured the shims and they were 0.5 mm . Should my next step be to increase the shims? If so, how much? and where can i buy them?
Are there any other way to adjust the mixture on the Injection pump.
I have posted pictures of the IP earlier in the tread.

Cant wait to get this car running right.
Thanks again.

ja17

  • Full Member
  • Platinum
  • ******
  • USA, OH, Blacklick
  • Posts: 7410
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #13 on: February 17, 2009, 04:56:26 »
Hello,
Make sure your linkage is correct or you will be unnecessarily mis-adjusting your injection.

You can temporarily make the oval shims out of paper or cardboard.  As long as they take up space they will work fine  and you can check your diagnosis.  Adding the shims will increase the fuel mixture at all speed ranges. Eventually you can replace the temporary shims with metal with  the required thickness.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

280SE Guy

  • Inactive
  • Silver
  • ****
  • USA, PA, Birdsboro
  • Posts: 316
    • some pics
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #14 on: February 19, 2009, 12:20:36 »

are there any gaskets in this device? I see one silicone gasket that looks like it was home made and one bottom metal gasket at the base.


Does anyone have knowledge of the gasket question?  The parts book lists number 002 997 38 40, "seal ring" but at over $90.00 from the dealer I'm struggling with the thought of paying that much for a piece of rubber or whatever it might be that would be about 7/8" diameter. Your experience on what you’ve done to successfully seal the WRD thermostat is appreciated. The BBB job 07-13 B4 states "Seal the heat feeler with Starrit", what is Starrit?
1971 280SE, 6 Cyl MFI, Anthracite Grey with Grey MB Tex

olaf

  • Guest
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #15 on: February 20, 2009, 02:33:58 »
My car finally runs like a champ.
Here is the conclusion. The engine was running very lean.
I first made sure that the linkages were aligned correct. After checking the WRD and making sure it was operating well I removed the shims that I had under it which measured 0.5 mm. I then made a copper gasket which was 2mm thick. I warmed up the engine before i changed it over and what a difference it made. All i have to do now is fine tune it with the small shims i have left. I believe i can play with it a little bit more but it is very close now.

Can anyone tell me what the spark plug should look like on these cars when running right and everything is tuned perfectly?

Even though the exhaust smelled like it was rich with fuel before i started, it was actually lean.

I thank you all for the great info i found on this site and the help you have given me. Super.
Next on my list is adjusting the valves and then redoing the springs and shocks.   

When I assembled the WRD I put a tiny little gasket maker silicone product where the thermostat sits in the WRD cooland housing. It worked great for me. and it looked like the person before me did the same when they were in there.



Benz Dr.

  • Vendor
  • Platinum
  • ******
  • Canada, ON, Port Lambton
  • Posts: 7219
  • Benz Dr.
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #16 on: February 20, 2009, 04:31:52 »
Spark plugs should be a light tan colour. The body of the plug may be slightly black but that's not a problem.

You did the right thing sealing the WRD. If you don't a small amount of coolant will always leak into the slide housing. When the engine is fully warmed the moisture will evaporate leaving a sticky residue. Not what you need in there at all. I use a bit of high temp grease in the housing.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

bpossel

  • Guest
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #17 on: February 20, 2009, 10:28:15 »
As I have been doing some more investigation on the IP, I have a question ....

If you add shims to the WRD, arent you in a sense running in a perpetual state of choke?
Shouldnt the adjustments for lean/rich be made on the main rack, especially if after the engine warms up, it idles nicely and you get a co reading within the ~3-4% range and the issue is mid range and above?

Comments?
Bob  ???

ja17

  • Full Member
  • Platinum
  • ******
  • USA, OH, Blacklick
  • Posts: 7410
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #18 on: February 20, 2009, 22:58:31 »
Hello Bob,

There are two stages to the WRD.  The top stage has the thermostat adjustment which are the  round shims or jamb nut adjustment depending on the year, under the WRD themostat (heat feeler). This stage in a sense is the choke. The next adjusment stage are the oval shims between the whole WRD assembly and the pump body. These oval shims effect only the rack in the pump and have no influence  on the the air supply to the engine. I would not consider them a choke adjustment.

The oval shim adjustment is a easy way for most to adjust the rack, it should not influence any change in air supply to the engine cold or hot. It is easy to do and easy to put back to original if the desired results are not achieved.

Yes, the rack adjustment is a good technique for the advanced student! A bit more technical.

Be aware that any adjustment to fuel mixture will also effect the mixture of the engine when hot or cold so a follow up adjustment at the top stage of the WRD may be needed to tweak cold idle afterward.

Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

bpossel

  • Guest
Re: engine runs rough when warm between 2k -3k Rpm???????
« Reply #19 on: February 21, 2009, 02:45:59 »
Hi Joe,

Thank you for clarifying the WRD and shims adjustment.  This helps!
Bob  :)