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Old 04-19-2024, 09:07 AM
Popeye Popeye is offline
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Join Date: Nov 2013
Location: Eastern MA
Posts: 33
Small running issues - 1971 250 / M130 engine

1971 W114, 250, M130 engine in stock configuration (Zenith 35/40 carburetors, stock ignition). New to me this past winter. It always has been well serviced – just not driven the past few years. I've driven 600 miles in the past four months.

Fundamentally the car runs wonderfully; it pulls strong, sounds good, shifts well. I have disassembled, cleaned, and reassembled the carburetors (with fresh gaskets/o-rings). I did not change any settings on the carbs - assuming the mechanic who serviced the car is smarter than me (I did a quick synchronization check - not perfect, but pretty close). I replaced the rubber vacuum lines in the carburetor and distributor. Fresh fuel filter. The feed fuel line from filter to carburetor appears original – I have a replacement on order from Mercedes Classic center. Other fuel lines on the “engine side” are new. I plan to replace the lines at the fuel tank, replace or clean the strainer, and clean the fuel level sensor.

I have two niggling issues, and curious where to start looking:

1. Starting the car is difficult. It takes two or three turns of the key to get it to start. Each turn of the key only a few seconds of cranking - in total 5-10 seconds of cranking to start. Then it runs a little rough/lumpy for the first minute or so: I have to give a little throttle to keep it running (1000-1500 rpm). Not violent. Then the motor settles into the “proper” high idle after 1-2 minutes, smooth as can be.

2. Initial tip-in of the accelerator results in a slight hesitation. When the engine is not fully warmed up – say after less than 10 minutes of running – the engine can stall if I floor it from a red light. Once the engine is properly warmed up, if I floor it from a stop it will jump a bit, hesitate, then accelerate really well. At higher RPM it drives and accelerates beautifully. The accelerator pumps on both carburetors provide a nice stream of fuel - but I have not measured the quantity, nor checked if the nozzles are pointed correctly.

Thoughts? My mechanical ability is decent, but I am clueless in the diagnosis. (I’m enjoying the learning process – and loving the car!)

Last edited by Popeye; 04-19-2024 at 02:23 PM.
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