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Fuel Pump


Michael Bonnar:
Fuel not getting to the carburetor
« on: Today at 02:42:53 PM »
Hello, I have a problem starting my 1950 170S Cabriolet, we poured gas directly into the carburetor and the car turnes over until the pour is gone. My brother in law took the fuel pump off and I took it to a mechanic to see if it  could be rebuilt. The mechanic attached a four foot hose to the carburetor and the end into a can of gas. He pumped the fuel pump a few times and the pump proved to not be the problem. I am asking that if there is anyone out there that can recommend the next steps to locate my problem. I have to let you know that it's been about at least 6 months since I've started this vehicle.


Mike Bonnar
Lambertville, Michigan
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Scott Montoney:
I am not familiar with the 170 fuel system, but from what you have tested so far, I am wondering if it would be possible to temporarily attach a section of clear hose to the intake and output of the fuel pump while in operation in the car?  I am wondering if you might see excessive air bubbles in the intake side of the pump or the output side that might indicate an air leak, and therefore insufficient fuel delivery?
Or the float valve may be stuck closed?

Michael Bonnar:
Thank you Scott, I will have my brother in law check that out, I apricate your impute!   

Hello Michael

On my opinion just two points before searching a carburator issue  :

Point 1
Our M136 fuel pump is working on two »axels » the debit and also the pressure
Did your mecanician had verify the two points ( seem only the debit...) ?
For your perfect information ( sourcing MB repair manual )
The pressure head is 0,19-0,24 atm
The delivery  36 L/h at the camshaft  speed of 1500 rpm and a float valve of 1,5 mm dia
The fuel feed pumps are gauged at a suction head of 0,75 m

Point 2
My own 170S is running at this time (perfectly) with an electrical fuel pump , if you want to test your mechanical pump , you can find an electrical pump and do the test without the mechanical pump...

Hope it can help you
Best regards


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