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1980 450SL 107.044
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14 Posts
Discussion Starter #1
Some years ago, I inherited a 1980 450SL which had been bought new by my father. It has been parked in my shop for two years since it last ran.

I put in a new battery (900CCA, AGM, $250, ouch) and no luck in starting. Sprayed ether, Benz ran as long as ether held out; clearly a fueling problem. Checked fuel pump, it was very warm but did not sound like it was running. Disconnected battery.

I clamped the 15mm fuel feed hose, pulled out the accumulator/filter/pump/damper arrangement, and took the pump to the bench. Hooked up to 12v supply, would not run. Frozen!

I filled the pump with a mixture of Liquid Wrench and Marvel Mystery Oil (I've had good luck using this potion on frozen electric Bosch pumps on fuel injected VWs). Soaked overnight, dumped the mixture from the pump (very dark). Filled pump with a new batch, soaked one more overnight. Next day, hooked up to 12v in reverse, and the pump blew out more darkened mixture. Hooked pump up (normal rotation this time) to a reservoir filled with more LW/MMA mixture, and it ran fine.

I replaced all of the flexible hoses between the fuel tank and the supply/return lines in the rear of the car. About $90 for all, including new clamps, from the MB dealership in Atlanta. Cleaned accumulator and damper, replaced fuel filter, put the whole thing back together.

Drained crankcase, replaced filter and put in 8.4 qts of Castrol 20w-50. Checked differential (full) and ATF (full, looked and smelled OK). Hooked the battery back up, turned the key a few times, and it fired up after about 30 seconds. Road tested, no leaks, runs great! One more oil/filter change, drain and refill differential and ATF (and filter) and I believe we are back in business.

Tomorrow: replace coolant hoses and drive belts, and wiper blades. Fix passenger side mirror and automatic radio antenna. More vigorous road test. Soon: New tires.

I hope this helps someone who may encounter similar problems. I will be happy to post part numbers for the fuel lines, should anyone find them useful.
 

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Registered
1980 450SL 107.044
Joined
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14 Posts
Discussion Starter #4
Sad to say, the fix was only temporary. A few days in, the fuel pump started howling, so I'm going to have to put in a new one.
 
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