250c - trouble keeping it running -Bad Gas? - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 09-11-2013, 12:01 PM Thread Starter
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Date registered: Sep 2013
Vehicle: 1972 250C
Location: Vermont
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250c - trouble keeping it running -Bad Gas? Sitting for two years

Considering the purchase of a 72 250c. Car has 62K miles. Driven 2K in 8 years. Sat for the last two. Car started right up after sitting for two years. Now it does not run smooth - need to pump the gas other wise it dies.

I spoke to a mechanic. He thought the carbs would need cleaning or be rebuilt. He also thought the tank might need to be pulled and gas and sludge removed to correct the problem.

Besides the old gas issue should I be looking at other solutions as well. Help me if I'm wrong but if it is a gumminess, bad gas issue is potentially a worst case scenario rebuild of carbs and pulling the tank for cleaning?

By the way, after the car started to run poorly, a new set of plugs and fuel filter was installed. No change in performance.

This would be my first MB purchase. All and any help appreciated.

Last edited by mbvt; 09-11-2013 at 12:17 PM. Reason: change headline
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post #2 of 3 (permalink) Old 09-11-2013, 12:25 PM
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Date registered: Aug 2006
Vehicle: 1972 300SEL 4.5, 1971 Citroen DS21, 1995 Jaguar XJS
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Prepare for all the mechanic said and more to get this car on the road properly and reliably.

The Zenith carbs have a bad rep, but if you know them they are not that bad. Make sure your mechanic is familiar with the Zeniths or you could end up down a rabbit hole with them $$ wise.

Once gas goes bad, it's best to drain it out before starting the car. If you start the car on the bad, old gas, you will draw it into the fuel system and the carbs and likely gum them up.

run the car off new gas from a can by the fuel pump and see if it clears up.

these are wonderful cars and if you have a good mech. and do some research I am sure you will love the car, it sounds like a beauty!
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post #3 of 3 (permalink) Old 09-12-2013, 12:20 AM
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Date registered: Sep 2012
Vehicle: 300sel W109, 280S 70 , 220s 62. 230 66. Lancia Flavia 63.Pininfarina
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The zenith carbs are a bit finicky,also prone to warping but excellent carbs for these engines, the idle jet tube gets clogged whenever the fuel dries up,then a good clean of the idle passage will get them going .
One method is to remove the idle mixture screws spray generously into the screw bore and it should clean the passages.
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