Benz V8 CIS issues

Anyone have any idea what might cause the following: "Starts and runs but does not take throttle. Needs some injection work. "

Car in question is a 450 SEL 6.9

Is likely culprit the fuel distributor? It has " Newer fuel pump, fuel accumulator and misc. items."

If this is on a new 'ridiculous car' for yourself, please, post a build thread...

speaking of which, how's that biturbo going? Did you finally get a good motor put together?

Warmup regulator, vacuum leaks, low fuel pressure, dirt in fuel distributor, misadjusted sensor plate, late ignition timing, bad coil...

And thats just off the top of my head, as quick as I can type.

Argh... trying to remember if a CIS car will run at idle with a massive false air leak or if the metering plate needs to move even at idle. (I know Digifant ignores the airflow meter at idle, but that's EFI)

No matter what, it's not a difficult problem to solve. The pre-Lambda CIS units are ridiculously simple. Air goes in, that makes fuel come out, and there's a little warmup thingy bolted to the engine that makes the engine run richer when cold.

I've only ever seen one bad fuel distributor, and that affected only one cylinder, not all of them.

Raze wrote: If this is on a new 'ridiculous car' for yourself, please, post a build thread... speaking of which, how's that biturbo going? Did you finally get a good motor put together?

It's priced right - but I don't really need a project I need a commuter.

But damn, it is very tempting.

My wife would KILL me if it wasn't something I could drive to work next week.

Biturbo got put on hold to fix the Montero. Wife's surgery slowed fixing the Montero (engine is ready to go in, but torque converter is giving me fits getting it in, don't want to pull the trans to get it in), and the Fiat is pissed at me for spending time with the Montero. Fiat is running lean at part throttle to the point of getting really hot. Carb is clean, no vac leaks, I don't get it. So driving home every day in 100+ heat, with the heater on, while stopping to let it cool down drains me.

So I'm looking for something to get back and forth to work in (or something for the wife - I could drive her 190E 2.6)

I missed the I-Mark RS by a few hours. All the decent stuff is over priced and the crap is filling up Craigslist under 2k.

Somehow I can't resist "ridiculous cars."

I have a weakness. I read your post to my wife and she said "See! They aren't married to you and they know how you are!"

I had a w116 280se with those exact symptoms. I think it may have been a vacuum leak but didn't keep it long enough to figure it out.

6.9 engine parts can be crazy expensive, I think i would be scared of buying one that wasn't running.

Sounds like a vacuum leak to me. If you buy it an join the benzworld forum you'll find the help you need. A 69er isn't going to be a cheap commuter and 205/70/14v rated tires are only around 250$ each if you can fine them.

Honestly if it is cheap enough buy it they worry about it later. I'm sure the grassroots crowd can talk you around the issues of CIS. CIS is a really simple system once you understand it. I keep having weird airlock/comtamination issues every few months with my car. Fire the sucker up and take a stethescope to each injector and listen, they should all sound the same. If one doesn't sound right a quick check is to crack the injection line at the fuel distributor, when you crack it you should see gas and the engine should bog down. If you crack the line and no gas comes out it means either you have an air lock or plugged injector/fuel distributor.

Good luck potential m100 owner!

Vacuum leaks, are the biggest enemy to cis. My vote goes there. My car had been sitting for years and the warm up regulator was completely clogged with varnish. It ran o.k. like that. It runs so sweet now that I've went through everything.

Vacuum leaks first and foremost. Next is the O rings in the CIS dizzy rotting away, I saw several of those. The O rings are out there but not readily available as Bosch considered the fuel dizzy to be non serviceable (yeah, right). My theory: E10-E15 fuel attacks the O rings which were originally formulated to work with straight dino juice.

6.9's have stupid expensive air suspension. If it's sitting on the ground, run away.

Curmudgeon wrote: ). My theory: E10-E15 fuel attacks the O rings which were originally formulated to work with straight dino juice.

I'm afraid that I'm going to have to call BS on that, given the millions of CIS cars that live just fine on E10.

Yes, this is a major peeve of mine.

Okey dokey. Having seen more than one 1960's/1970's era CIS dizzy apart with O rings that had turned to sticky black goo, I suppose the O ring fairy just took a few weeks off when those were being made.

It's definitely not my imagination that the carburetor on my Ryobi weedwacker had ~zero~ troubles until E10 was introduced in my area around 2003 or so.

I'm not going to say E10 has cause all of the issues with CIS injection cars above and beyond contamination and neglect. The CIS injection system is very sensitive to fuel contamination and all of the fuel pressures throughout the injection system need to be within specs for a car to run correctly. A bunged up fuel distributor, faulty fuel accumulator, warmup regulator, etc can all cause drivabilty issues.

I guess you can service the fuel pressure regulator in the fuel distributor and shim it to bring the fuel pressure within specs but I hear splitting the fuel distributor to reseal is a job you need to have specialized tools to do.

6.9s don't have airbags, it's a hydraulic setup similar to citroens, and pretty much the same as the sls in newer (80s and 90s) Mercedes cars.

Sell the 6.9 to me, ill figure it out

I agree with the others. Most likely a vacuum leak. And the source of the leak is probably an air boot between the fuel distributor and the throttle body.

I promised I wouldn't drag anything home that I couldn't drive home.

http://sanantonio.craigslist.org/cto/3181446391.html

m4ff3w wrote: I promised I wouldn't drag anything home that I couldn't drive home. http://sanantonio.craigslist.org/cto/3181446391.html

Not sure I'm buying that that is a 76, it looks like a newer car, I think 76 was the only good year for these cars before the large bumpers got stuck on them. Am I wrong?

76 was when the ugly bumper requirements started, there were 1975 6.9s which probably didnt have them though.

Pretty sure 1974 was when the bumpers got ugly because the first two years 72 and 73 450sl r107 imported to the US had short bumpers with bumperettes.

I personally would hold out for a grey market euro 6.9er, they are hard to find but last one I saw sold for 2800$.

Pics of a later aluminum CIS dizzy disassembled:

http://mbworld.org/forums/e-class-w124/432492-m104-m103-cis-fuel-distributor-rebuild-process-pictures-heavy.html

Takes a while to load, but good pics of a cast iron VW fuel dizzy disassembled: http://forums.vwvortex.com/showthread.php?5194798-The-soon-to-be-daily-gets-some-EG-goodness

They aren't really complicated. The hard part is adjusting the thing properly during reassembly, the VW thread shows how the guy did that.

Aluminum = CIS-E, which this car won't have. Basically, it's all electronically controlled, there is no warmup regulator. (Mercedes used it until the mid-90s on some of their cars, Motronic-powered!)

Iron = CIS / CIS-Lambda, has warmup regulator. The old school setup.

IIRC CIS-E had an electronic injector at the fuel inlet side of the dizzy (think of it as a PWM solenoid for tighter mixture control), basically a bodge to get the cars through emissions testing while the multipoint systems were being finalized. Otherwise very similar systems.

If you rebuild a fuel distributor just be carefull to keep the springs and seats seperate as they are calibrated. I have never rebuilt one but have done the research on the job. It probably isnt' difficult but you have to be carefull not to mix up the parts. I would almost rather buy a rebuilt/tested unit for 350$ and be done with it because if you screw up the rebuild you can have real issues with your car. I keep having stupid bloggages in the fuel distributor and you really have to be carefull because a clogged injector port and you can damage a cylinder by running lean.