Tune up question

[GTSilver944]

My 2800CS doesn't like starting or idling when cold. Once it warms up, it behaves normally. I thought that I might do a general tune up and adjust valve lash, idle screw, etc. I'm very familiar with EFI, but this is the first carb-ed car (and BMW) I've owned. Anyone have a good write-up on doing this?

Thanks,
Max

 

[jmackro]

My 2800CS doesn't like starting or idling when cold. Once it warms up, it behaves normally. I thought that I might do a general tune up and adjust valve lash, idle screw, etc. I'm very familiar with EFI, but this is the first carb-ed car (and BMW) I've owned. Anyone have a good write-up on doing this?

Max:

I wouldn't discourage you from checking your valve clearance, and re-adjusting as necessary. But I seriously doubt it will improve your cold idle.

By "general tune up", do you mean replacing the points, plugs, condensor, cap, rotor? Again, that's worth doing if the parts are old, but if the car runs well when warm, I doubt the ignition is your problem.

To focus on this problem, I would address the carburetors first. I can't give you a detailed procedure, but would look at the chokes if cold-starting, cold-idle is the issue. Does your car have Zeniths or Webers? Reporting the carb make/model will help others to guide you further.

 

[GTSilver944]

1970 with Zenith carbs. I'll do some research and post back in a couple days when I have more questions. I was under the assumption that timing and valve lash should be properly set before adjusting the carbs. I'll look into valve lash and checking timing with a light (the Porsche's I'm used to have hydraulic valves and don't need timing lights - so this is new to me).

I've only had the car for two years and I'm unsure as to when things were replaced. Haven't driven it much as I've been replacing the clutch, clutch hydraulics, fuel and water hoses, etc.

 

[61porsche]

Carbs and cold starts

Jay's right. Show us a picture of the carbs minus the air cleaner.

There were several variations of Zeniths if that's what you have.

Electric idle stop valves or no? Cold start valves or not?

EGR- tubes connecting the carbs or not. Advance and retard distributer/ solenoids?

Chances are a previous owner/mechanic had monkeyed with them. All of them are old with old parts so the repair/ adjustment is just a guideline to what you should be looking for. They can be a wonderful carb when in tune; you just have to follow some rules about what they do and don't do.


Cold start- take off the air cleaner and watch what the carbs are doing or not.

Both chokes closing the same amount? Nearly closed?

Both chokes coming off ( opening) at the same time/ temp.? Idle coming down to normal?

Idle speed around 1600-1800 with chokes on? Idle speed at 1300 or so means one's not engaging?

Engine smooths out if you hold the rpms at 1800?

Choke covers and rich setting- about the same? The setting in the manual could be wrong depending on the specific carb.

Didn't say where you lived: different ( a little where you are) for adjustment.( really hot or very cold or mountains)

Too much choke- dark plugs/ exhaust at start? Dribbling fuel or sounds like bacon frying with idle that goes up and down a little? Zeniths are sensitive to fuel level and just throwing a washer on the float valve probably won't work most of the time or for very long if you don't adjust them on the car due to fuel pressure/ old pumps/ etc.

Tell us all you can.....go by the numbers and they'll work just fine. But there's a dance you have to go through to set them up and adjust them.


There are some good supplemental info on the carbs by the factory-or have you found the Mercedes Zenith manual? Happy to scan an email mine.

61Porsche
Yeah, with dual Solex carbs.

 

[bengal taiga]

My 2800CS doesn't like starting or idling when cold. Once it warms up, it behaves normally. I thought that I might do a general tune up and adjust valve lash, idle screw, etc. I'm very familiar with EFI, but this is the first carb-ed car (and BMW) I've owned. Anyone have a good write-up on doing this?

Thanks,
Max

I agree with the others. Given your description, it is unlikely your valve lash is causing cold run issues. However, if you are driving the car and especially, if you are pushing the revs, you should not ignore the valves. If for no other reason than peace of mind, you should check them.

There are many "how tos" just fingertips away. Checking and adjusting valve lash is considered "routine maintenance" and covered not just in the shop manual but also in the "owners manual."Same with ignition timing. The manual even recommends an interval for checking the lash. A copy of the owners manual is available on this site (p71?) http://www.e9-driven.com/Public/Library/Documentation/Owners Manual/3.0 CS-CSI Owners Manual.pdf

So is the more comprehensive repair manual: http://www.e9-driven.com/Public/Library/BMW-E9-Manual/pages/en/index.html

And while your exploring your carburetors, you might want to look here: http://www.e9-driven.com/Public/Library/BMW-E9-Manual/pages/en/13.html#refertoc

Naturally, there are other variations on the same theme: Autobooks, Haynes and Chilton, to name but a few.

Here's even more: http://www.nmia.com/~dgnrg/page_5.htm
http://www.bmwe34.net/E34main/Maintenance/Engine/valve_adjust.htm

http://www.youtube.com/watch?v=_ubwFXgU_nM&feature=related (Note: This method is a little unorthodox as adjusting valve by measuring between rocker and cam is not depicted in most repair manuals. Perhaps because inserting feeler gauge on the cam may tend to introduce grit and/or scratch the cam surface.):?:

 

[bill]

Don't overlook a leaky head gasket. For years I played with the Zeniths, switched to Webers, electronic points, valve adjustments, and nothing cured my misfiring/stumbling problems until I finally pulled the head and replaced the gasket. Sounds like your situation may be similar. With the engine cold, it would misfire and run rough until it warmed up, then the misfiring would settle down and sometimes disappear. New gasket, no problems.

 

[GTSilver944]

Thanks everyone. I'm in Denver at the moment and the car is in Memphis. I think I have enough info at this point to start. I'll report back at the end of June once I'm back in Memphis and can check things out. As of right now the to do list is: points, plug wires, valve lash, verify timing, then check out the carbs. I realize that it is carb related, I'll simply get the other things out of the way first.

I don't think it is a HG - no white exhaust or sweet smell. I honestly haven't driven the car enough to determine if it is losing any coolant. I just replaced the water hoses and it's not leaking, so if there was coolant loss it would have to be HG related.

Also, does anyone carry a vacuum line kit? Might as well replace those while I'm in there...

It's my father's car. Hopefully I can get it to the point where it could be regularly driven before I leave the country a few months...