Ryan,
The wire that is hot with the key in the run position is called run or ignition. Of the two wires on the same side of the 0.4 resistor, one probably goes to the box and the other should be from the start terminal on the key or the starter. It will only be hot while the starter is turning.

Michael

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Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120

Thanks Michael, you were right. One of those two wires was hot with the starter engaged - the other must be going to the control box. I have the wiring and the ballast issue figured out - now for the hard part, fitting all of the stuff inside the distributor. The guy at Crane mentioned boiling the plastic shutter wheel for a couple of minutes to help get it slid over the cam lobes - it is really tight and he warned me that it would be a very tight fit (he even offered to send me a spare, just in case I broke one). Other than that, what other problems should I be aware of? He mentioned something about a problem getting the optical part attached becasue of the screw hole not aligining, but since I haven't got that far yet, I'm not sure In know what he is talking about.

Thanks, Ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

Well, I finally got the Crane installed, but it wasn't easy. I have a way of complicating jobs and as something of a catharsis I am going to tell you the dumbest thing thing I think I have ever done while working on a vehicle.

I put a large socket wrench on the crankshaft bolt to turn the engine to TDC to set the timing on the optical shutter. The new cranes have an LED light that allows for a much easier installation - you turn the shutter, with the engine at TDC, just until the LED lights up and your good to go. Anyway, I get the shutter adjusted right and w/o thinking, jumped in the car and started cranking -- with the wrench still on the crankshaft. The wrench tore through both of my AT cooling hoses and got lodged in the radiator fan. Fortunately, I got the wrench out w/o damage and ordered two new hoses which I got yesterday (I'm telling myself the old hoses were bad and needed replaced - somehow it seems to help).

Anyway, car runs great (I checked the distributor phasing per the Crane manual by cutting a hole in an old distributor cap and everything is lined up perfectly). I still have a problem with periodic carb backfire, so I am back to the Zeniths, but it is clear that the lurching is gone and that the car feels and runs better. I am going to take off the top two sections and clean everything this weekend and pay particular attention to the accelerator pumps and the needle valves. I seem to notice the backfire after the car warms up (from a cold start it runs fine) and when I turn a corner or go up an incline, so I'm thinking maybe float level??

Thanks for the help.

Ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

That setup with twin carbs should have two non-obvious solenoids, one each at the base of each carb. They are "on/activate" with the ignition switch in "run" and off/deactivated when the key is off. These were early low emissions cars and the solenoids purpose was to prevent run-on due to a very lean mixture, after shutting off the engine. I.e. they shut off the idle circuits.

So with the key off, you can spray gumout, etc. through the passages till you turn blue, but with the solenoids in the off position they effectively prevent carb clean-out from reaching all passages. Ususally the fine carb passages will gum with all the symptoms you posted.

Trick- have someone turn the key on and off, without starting engine, while you are positioned at the carbs, and you should hear the solenoids opening/closing (on/off). Turn key to on, which should open the solenoids, unstopping the idle passages and then clean all the small idle circuit passages. You should be able to observe carb cleaner emerging from the small passages down inside the carb throat.

DO NOT use fuel that has any ethanol, as the ethanol reacts with the carb pot metal making a gray gum...which gums up and plugs the idle passages in short order. Symptom is non-existant idle and stalling. You will need to keep your foot on the gas to keep the engine running at slow speeds.

Soooo...ensure the solenoids are a) present, b) operating, c) activated when cleaning the idle circuits. That should go a long way to alleviating your problem. P.s., caused an rear ender accident, when first diagnosing this vexing problem.

The solenoids can be a real pain but once you are a fair way off idle the idle circuit is no longer working and you are into the main jets.
If your probelm is closer to idle than not, fiddle with the solenoids. Don't foget to check the wiring also. As the engine moves, you could have an intermittent connection. If it were deeper into the throttle, I'd check float level.
A poor mans method for checking for a lean condition is to smell the exhaust. If it burns your nose and makes your eyes water, it's running pretty lean. You can also pump the brakes while stopped and take note of what happens to the idle. If it smoothes out, it's probably running a bit rich. If it gets stumbly, (new word for ya) it's running lean.


If you have not done so yet you need to check this out, especially section C troubleshooting.
http://www.jaimekop.com/CarbManual/

Michael

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Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120

Those solenoids can be a real pain and if fuse #4 blows so go they and the car won't idle (or run below about 2500 RPM) period. I removed mine, cut off the tops and removed the electrical innards. Plugged the hole in the bottom with a 4-40 cap screw and filled the cavity with JB Weld. Reinstalled the solenoids and never had an issue after that and the car never tried to "run on" after shutdown. I don't remember if my Webers had them or not but if they did I did the same thing to them.

Worked for me.

Dan

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Dan Taylor/ Tulsa, OK MBCA
'84 300D/'90 Jaguar XJ6/XJ40

Solenoids are OK - I had some issues early on with them in this car and after tracking down some extras at a junkyard in KC, I discovered a blown fuse, as mentioned by Dan. An easy way to check them is to turn key on and disconnect and reconnect them - you should hear a clicking sound each time. As far as rich/lean - I just can't tell. I notice no difference in the idle when depressing the brake and my nose must not be very in tune. Anyway, I did clean it out as mentioned - with the key on.

I would like to track down an exhaust gas tester, but $$.

Ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

I have this tester. It works well but be prepared for it to feel like a toy. It only weighs a few ounces at the most. I also have the Ezibleed and it works very well.
You might check with local indy or high school auto shop to see if they will set the mixture for cheap.

http://www.aep.bigstep.com/digital1.htm

Michael

__________________
Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120