1972 250C Crank, but no start - Mercedes-Benz Forum

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post #1 of 7 (permalink) Old 01-17-2016, 07:00 PM Thread Starter
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1972 250C Crank, but no start

Hi everyone,

I just recently purchased a 1972 250C, all original parts. Original Zenith carburetors.

The car was parked for about 2 years. It cranks, but does not start. The crank sounds promising though, but just doesn't catch. The interior, exterior, and engine were very dusty with some leak from the power steering, I've cleaned all of that. I looked at the spark plugs and they look good.

I'm currently in the process of changing the oil and oil filter.

What are some typical issues to check for if it cranks, but doesn't start?

I want to make sure, it's possibly the carburetor before I go and rebuild it, or replace with the newer Weber ones.

Any help and troubleshooting recommendations would be great!

Looking forward to hearing from you guys.

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post #2 of 7 (permalink) Old 01-18-2016, 05:30 AM
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Quoted : I just recently purchased a 1972 250C, all original parts. Original Zenith carburetors.

I had a 73 280c and recall a fuse going bad, that was used to do something to the zeniths.

A warming system, if I can recall.

It has been years, so I can't recall where it was located, but start looking in the fuse box, I think that was where it was located.

Nice car though, they always reminded me of a RR coupe.

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post #3 of 7 (permalink) Old 01-18-2016, 07:22 AM
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Typical path is check if you are getting gas and spark first. if you push carb linkage can you see gas spray down throat? if you disconnect fuel line at carb does gas come out? simple check is there spark at plugs? is there spark from the coil?

Zenith's work just fine when adjusted, Webers create a different set of issues.

Let us know answers to above questions and we can go from there.
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post #4 of 7 (permalink) Old 01-18-2016, 04:44 PM Thread Starter
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I haven't been able to check today.

The car now does not crank today, its just quiet and does nothing. Sounds like some electrical ... relay or fuses problem now?

Took the battery to get checked everything was good. Tried another battery same thing. Lights all work so the battery is working.

I've changed all 12 of the fuses in the box.

Where else can I check on this car for such problem?
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post #5 of 7 (permalink) Old 01-19-2016, 09:07 AM
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If it cranked before and no longer does, my thoughts go to the starter or the starter solenoid. Do you think maybe you let it crank for too long while testing the carb?

If you want more info on your carbs, take a look at the Online Resources portion of the forum, last or second to last page. Lots of stuff there about the Zenith carbs.
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post #6 of 7 (permalink) Old 01-22-2016, 03:16 PM
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If the car sat for 2 years, the gas is probably no good and there might be varnish in your carbs also.

Get a sample of your gas and smell it. If its bad you will know it. It won't smell like gasoline at all.

1999 CLK 320
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post #7 of 7 (permalink) Old 01-23-2016, 05:50 AM
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If you get nothing, not even a click, when you turn the key, it could be a bad neutral safety switch. Try wiggling the shifter in P and N and see if that helps.

As to your other issues, test for spark with a timing light once you get it cranking.

If you have spark, then check for fuel by loosening a line at one of the carburetors and crank. If no fuel there, try blowing some air into the tank by disconnecting the tank line at the fuel pump. Obviously you need some sort of compressor to do this.

Once you get fuel to the carbs, see if you get a squirt from the accelerator pumps as mentioned before.

Chuck Taylor
Falls Church VA
1998 SL500
1959 220S
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