Mechanical Fuel Pump Question 250c 1972 - Mercedes-Benz Forum

 
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post #1 of 5 (permalink) Old 01-22-2016, 02:50 PM Thread Starter
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Mechanical Fuel Pump Question 250c 1972

I have a questions for a Mercedes 1972 250C

I'm not able to get gas to the fuel pump.

I have disconnected both inlet and outlet and have had someone crank the car to feel if there is pressure coming from either side. This is brand new mechanical fuel pump. Neither side is giving pressure.

Should the pump be working during the crank?

What else could be wrong?

Thanks
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post #2 of 5 (permalink) Old 01-22-2016, 02:58 PM
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Pump should be working when cranking.

Do you have fuel coming out of the incoming fuel line. If not, possibly clogged fuel line or tank strainer.

Don't know much about your particular pump. From the picture, it looks like a diaphragm type pump. Are there check valves built in? Can you blow in one side and not the other? If you can blow in both side, I would think the pump is defective unless there is an inline check valve somewhere else.

Last edited by 260e crusier; 01-22-2016 at 03:44 PM.
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post #3 of 5 (permalink) Old 01-22-2016, 03:16 PM Thread Starter
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I'm checking right at the pump. No lines connected to the pump. There is no pressure from outlet or inlet. So I haven't even checked the fuel lines yet.
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post #4 of 5 (permalink) Old 01-22-2016, 03:37 PM
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Originally Posted by billyjobs View Post
I'm checking right at the pump. No lines connected to the pump. There is no pressure from outlet or inlet. So I haven't even checked the fuel lines yet.
You cannot get gas to the fuel pump UNLESS there is gas in the fuel line.

Without any lines connected to the fuel pump, you may or may not feel a little air pulse. You're not going to see any significant pressure. If there are checks valves in the pump, they would seat better with fluid than air.


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post #5 of 5 (permalink) Old 02-03-2016, 06:28 PM
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If you moisten two of your fingers and put one finger over each of the ports on the FP while cranking, you should feel a little suction from one and pressure from the other. Next step would be to get a small bottle with gasoline and a hose connected to the pump to test if it's pumping.

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