280c Carb Update - PeachParts Mercedes-Benz Forum

PaVarrieur · #1 02-05-2003, 10:21 AM

Okay this will be a little long winded.
After e mail correspondence with gympie, I decided to check a few things before attempting the dreaded Solex rebuild. gympie's suggestion of checking chain stretch was taken to heart. Here is what followed. Upon starting the car this past saturday, it was obvious that it was only running on 5. I decided a major tune up was in order. The following was done.
New Fuel Tank Filter
New Fuel Line Filter
New Plugs
New Distributor Cap
New Rotor
New Plug Wires
New Points
Check Camshaft Timing for chain stretch (perfect)
check ignition timing.
The car runs the best it has ever run in the six months I have had it since its purchase on E Bay. ($2900.00) There is nothing apparently wrong with the Solex.

What is wrong:
1) Despite removing and and re indexing the distributor, I cannot get it to time out at 4.0 atdc. (this spec comes from the cd rom)
There is a small index mark between 4.0 and 5.0, is this the correct timing index for a 1974 110 federal engine?
All adjustments made to the distributor have been done with the engine at tdc., but the best I can get the engine to time at is 2.0 atdc. Any adjustments to the distributor to acheive a 4.0 result in the engine not running.
2) Point gap. The spec for the points is 34 degrees of dwell. Since my dwell meter is on the fritz, I have set the points with a feeler gauge @ .019, would this setting have any effect on the ignition timing?
3) Can you believe that a condensor for this car is $42.00 list from Mercedes, and not available in the aftermarket, while all other ignition parts are!
4) I had to jury rig the ignition wire from the transistor to the distributor, as this part is only available with purchase of a new distributor.
Any help on the timing issue would be greatly appreciated. I would love to get the timing perfect

#2 02-05-2003, 01:37 PM

The timing of a '74 110 Federal should be:

Bosch distributor no. 031 310 002

4° after TDC with the vacuum connected

7° before TDC with the vacuum disconnected which should be the starting speed.

On some 110's such as mine has a needle pointer which comes off the water pump housing. This is used a the timing reference mark to the markings on the vibration damper. If you have set the timing @ the |0| mark, the rotor should correspond to the notch on the distributor at number 1 firing position.

Would recommend using a dwell meter on your dwell when you have a chance. It will come in handy to check the variation in dwell which is caused by the wearing of the intermediate gear shaft and the helical grear shaft. A bad intermediate gear is the worst enemy of a M110.

Don't fret much about the condensor. MB reccomonds that it be sniped anyway, as it causes greying of the points.

Good to hear the timing chain is in good shape!

ctaylor738 · #3 02-05-2003, 01:53 PM

.019 is pretty fat for a point gap, which may be why you can't get the timing right. Suggest you go to .012 and try the timing again.

As Gympie says, forget the condensor.

I may have an extra wire - I will look tonight. You need the green one, correct?

PaVarrieur · #4 02-05-2003, 02:56 PM

Thanks for the quick reply guys.
I performed the indexing of the distributor exactly as gympie says. I have re-installed distributors on everything from Aston Martins to Volkswaqons, all are done the same. So I cannot figure out why I cannot acheive 4 degrees after tdc. With 0/0 on the damper and the camshaft indexes all lined up, rotor over the distributor notch, distributor in the middle of its adjustment slot, the engine will run, very slowly, when the distributor is rotated counterclockwise, it bottoms out on its adjustment slot and will only reach an indicated 2/0 atdc. Perhaps the mechanical advance is not operating properly. I know the Vacuum advance is working.
Oh well, I will figure it out. I won't let it beat me!
Chuck, If you have an extra wire, let me know. I am obviously in the market for one. I will also re adjust the points per your advise.

Thanks again

#5 02-06-2003, 12:28 PM

Gosh that is perplexing. Have your tried setting the timing to 7° before TDC without the vacuum connected, then connect the vacuum and the advance should bring it to 4° ATDC.

Almost the same thing happend to me when I discovered my timing chain going south or north. With an advancing timing light I set the timing to 7° BTDC, then advanced the timing light to see if 7° advanced would bring me to TDC. To my surprise it did not, it was way off. A bad timing chain will retard the timing, causing the distributor to be moved near its limit to have the engine being timed.

But then again, it could be the mechanical advance as well. A distributor shop could test it for you. Most of the "muscle" machine shops have a distributor tester.

PaVarrieur · #6 02-06-2003, 12:59 PM

My money is on the mechanical advance. I see no problem with the chain as it always comes up to the index marks on the camshafts. I turned the engine over a number of times, both by hand, and with the starter motor and it was never off. There is absolutley no slop in the chain whatsoever. Funny thing. The car runs so good I almost do not want to fool with it. I usually follow the adage: "Don't improve it into a mistake".
I will also try your disconnected vacuum theory.

#7 02-06-2003, 01:22 PM

The mechanical advance sure could be it. You have surely ruled out the timing chain. One other thing came to mind. The damper itself has rubber innards. Understand it tends to come appart on some M110's. Just wonder if your damper is off a bit.

BTW, looking at a '87 BMW 528e. Any suggestions on what to check before I commit myself?

PaVarrieur · #8 02-06-2003, 06:07 PM

Sorry,
My knowledge of 5 series BMW's is limited to the E34 Series, (1989 thru 1995). I do know that the ETA series engines were low horsepower high torque engines. Some of the earlier versions used a thermal reactor in the head upstream of the exhaust manifolds. They were prone to head cracking. I'm not sure if your E28 is of this ilk.
I would try this address: techtalk@roundel.org or jmorgan@roundel.org. Ask what to look out for. They should be very helpful. They are both via the BMW car club of America magazine, The Roundel. I have been a member since buying my 1990 E34 new. It is a great magazine, and they have helped me out in the past.

#9 02-10-2003, 09:05 PM

Thanks for the information. Checked on the BMW and sure enough, it had a leaking head gasket and broken head bolts. Guess this is common on BMW's. Don't understand why BMW did not recall them.

Anyway not to turn this into a BMW posting. How you comming along on your 280C?

PaVarrieur · #10 02-11-2003, 03:51 AM

Unfortunately, I have been too busy with other projects to concentrate on the timing issue. It is running so good right now that I have not worried about it that much. The shift indicator cable seems to have broken as of yesterday, and while not a major mechanical problem, it is still irritating. Ever dealt with this gremlin?

ctaylor738 · #11 02-11-2003, 09:10 AM

The cable is a major PITA. They all break in the same spot and the used ones aren't very reliable and the new ones are expensive. The best suggestion I have seen is to replace the cable with monofilament fishing line.

I replaced mine with a floor shift.

PaVarrieur · #12 02-11-2003, 09:53 AM

Chuck
Thanks for the "encouraging" words re: shift indicator cable. I have a new speedo cable from a deceased chevy van that I might attempt to use. Did you find the spare ignition wire?