distributor help 72 250c - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 10-05-2005, 08:42 PM Thread Starter
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distributor help 72 250c

hello ,just a quick ?.when i pull of the advance hose on the distributor the car stalls out.is this normal.someone has removed the retard hose and has disconected the two vacume valves.I checked the diaframes and the seem to work fine so im going to hook them back up.will this help the performance of the car,or do people always take them off.thanks
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post #2 of 3 (permalink) Old 10-05-2005, 09:19 PM
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RE: distributor help 72 250c

I'm assuming that you're doing all this with the engine idling. If that's the case, disconnecting the vacuum-advance hose shouldn't cause enough of a vacuum leak to stall the engine. In fact, the vacuum-advance line should be connected to "ported vacuum", not "manifold vacuum", and the ported vacuum connection shouldn't have much vacuum at idle(less than 5").

To really figure out what's wrong and to fix it, you'll need a tachometer, a timing light, and a vacuum gauge.

With all the hoses connected, your idle should be 800-900 RPM in neutral once the engine's warmed up, and the stock timing at idle with the hoses connected should be set to 4 degrees after top-dead center (ATDC). Once you get everything sorted out, you can actually advance the timing quite a bit, but since you're having problems, you're better off starting off with the stock settings.

At idle, measure the vacuum at the vacuum-advance line at the distributor (should be very low), and also measure the manifold vacuum. You can test the manifold vacuum by disconnecting the seat-lock hard vacuum line (the dark blue one) from the rear of the intake manifold. The manifold vacuum should be at least 15" at idle.

As for the vacuum-retard lines, they're mostly for emissions-control purposes, along with the very-retarded initial igntion timing. Once you get everything sorted out, you can probably bypass them, but if they look good, you may as well leave them connected while you're troubleshooting.

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post #3 of 3 (permalink) Old 10-06-2005, 04:53 PM Thread Starter
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RE: distributor help 72 250c

ok ,adjusted timing car will run with hose disconnected.what is ported vacaume?.IM getting about 18" from the hose coming from the carb.in my vavaume gauge says this is good.if i turn the distributor clockwise it lowers to 14-15,but on my gauge says to advance timing.the car will not idle with the hose disconnected at 14-15".this is the hose that is connected to the distributor.I can find any other hoses that are small to hook up to.
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