The auto: 1976 280s, DOHC 6 cylinder, 4 barrel Solex carb

The problem: The engine dies. It has happened 3 times in the last 2 weeks. 2 times after driving a short distance then turning off the car. When I try to restart it takes a long time, but finally does start. This week after a short trip, it cranked right up ( as usual ) then died after about 2 blocks, while setting a stop light. It cranked up again, but took much cranking. Also last week, it would not start in the morning. I had to crank a long time and pump the gas pedal, but it finally did start and ran fine.

The really odd part is that when it dies it happen with no warning of any kind. There is no odd sound or feel, no missing, no shudder...it just dies. In fact, it seems like it actually quits running even quicker than when you turn off the ignition.

My mechanic thinks it is an electrical problem of some sort. Any thoughts, suggestions, comments or questions would be appreciated.

These are the things I am checking:

ignition switch
coil
points ( for sticking open, this happen to me once 25 years ago, and took forever to figure out)
shut off solenoids in base of carb
all wiring
fuel pump

Thanks
Stephen C. Stierstorfer
acje@flash.net

P.S. Feel free to respond via email.

Your symptoms would fit a vacuum leak. Do you have a vacuum guage?

Good luck,

Stephen:

I tend to agree with your mechanic that this sounds electrical. I am somewhat familiar with this body type but only from '72 back. However, "assuming" that you have the Transistor Controlled Switching" unit that actually controlls the firing of the coil you might want to have that checked. It "should/may" be located under the battery and just behind the headlights on the drivers side. Check to see that the ground wires from the distributor and condensor are in good shape. Corrosion caused by battery acid can attack the connectors on the TCS unit and this could cause what you are seeing. Also, make sure that you have good wiring from the ignition ballast resistors (should be two of them) to the TCS and back to the Coil. Might check the ballast resistors with an Ohmmeter.

My experience with the fuel shut-off solonoids is that if they fail then you get a car that won't idle (rock-n-roll) but runs "OK" at speed (since the idle circuit is out of the loop at that point). You can start a car with the solonoid(s) bad (or if the fuse is blown) but you can't keep it running except with a lot of throttle. You will recognize this condition if/when you ever experience it.

I basically made mine into "dummies" so I don't have to face this problem again.

Anyhow, I think you need to take a good look at the electricals.

Fuel pump?? Dunno, I would think that if the fuel pump was bad your engine would not just quit without going thru the usual "help, I'm running out of gas symptoms".

My .02.

Dan

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

I am very interested in the outcome of this problem. I am experincing the same. i've had both of the carb's rebuilt on my 280s 6cyl. after reading some of the posts , the common link seems to be the ignition control module. I have read that 1971 is the first year that module was used? also, is there a way to by-pass this module? thanks in advance for any input.

MY 1992 500 SEL had the same dying problem.It was as if someone turned the key off. Dealer replaced ignitor,no problems since.Hope this helps.

LRB:

IMHO there are two way to bypass the TRC. One would be to replace the ignition system with an modern unit such as the Crane 700 (which I use) or the Pertec. Cost would be in the $100 range.

The other is to physically bypass the unit itself (as you asked).
I don't have either my car of any schematic here at work, but if you wanted to physically bypass the unit, you would have to run a wire from the output of the ballast (second?) resistor to coil(+) then disconnect the brown wire from coil(-) and the wire from the distributor (black or green???) to the TRC unit. Run a new wire from coil(-) to the point on the distributor where you removed the connection to the TRC unit. That should work. In effect, you would have a standard breaker point system. Only thing I cannot be sure of is the relationship between the Bosch coil and the ballast resistors but it should not hurt to have them in the circuit. Not sure if the Bosch coil has internal resistance or not.

I put the Crane on my 71 250C AFTER I did the Webbers and it made a difference even then. "Off idle" performance much better, quicker starts, less maintenance on the plugs, better idle (and the idle was pretty good when I put the Webbers on) and I have not had to reset the ignition timing in over three years.

Just my opinion here - "your mileage may vary"...

Dan

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

thanks for the info . I haven't even thought about changing the ignition system.

by the way, what model mercedes would I find a Crane 700 ignition system on?

Crane is an aftermarket manufacturer of ignition components. You won't find their components as standard equipment on any MB.