1967 250SE Start Issue
 

After replacing brake and clutch lines (dang I hate DIN bubble flares!), our customers 1967 205SE won't run. It ran a week ago when it came into the shop, but we never really tested it as it had no brakes or clutch.

It cranks normally, starts to run, then stalls. Engine fires very quickly while cranking - but quits after 1 or 2 seconds, and yes, we did check for gas in the tank and even added a couple of gallons.

I am not familiar with the mechanical fuel injection system used on this car. :(

Ideas on what issues to look for or pointers on where to look for information would be greatly appreciated. I've searched the archives on this forum but came up with zip, probably used the wrong search terms.

Henry

They can foul the spark plugs quickly due to excess fuel and/or oil burning. The mechanical injection does not meter the fuel nearly as precisely as today's electronic systems and they can foul the plugs in a hurry especially on short start-ups that do not reach full temperature. Pull the spark plugs and look at them, if dirty at all, replace them.

The fuel injection is not likely the problem and making adjustments to it is not recommended unless you really know the system.

The distributor is just a point system, check for spark and if there is spark try a set of plugs.

Can you hear the fuel pump running? It is fused in the fuse box on the L/F fender IIRC.

Good luck!

HP:

Try this:

1) Remove the negative (points side) primary wire from the coil.
2) With the key ON, check for battery voltage, working backwards from coil positive to the battery. The symptoms suggest a fault with the primary circuit. It may be intermittent; shake wires and the ignition switch.

The easy starting suggests that the resistor bypass from the starter motor is OK, but that the run circuit has a fault.

if replacing the plugs, ensure they match the wires. Classic Benz wires have a "large" impedance and the plugs are the 0 resistance type. Current Bosch books say to use resistor plugs, but that's because the also recommend lower impedance wires to compensate. There's a spec for overall impedance from cap to plug tip.

Also, the plugs are ideally copper, not platinum. As the small tips on the platinum plug foul in those motors.

BTW, the fuel pump at the rear is rated for high volume, but low pressure. In that regard it's very different from today's pumps and it is subject to clogging from gunk in the tank. You might want to clamp the hose between the tank and the pump and then disconnect it from the pump to see if it's clogged up with rust and junk.

-CTH