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Engine loss of power going up steep hill.

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Scott Montoney:
Ok, it's my turn to request some input. . .
Yesterday I was out for a drive on a route that I frequently take through the countryside.  Sections of the trip are up a fairly step, but short, hill.
As I got near the top, my engine started to jerk and loose power.  I was just able to get to the top and then it smoothed out again.  I have had this similar action once when I was very low on gasoline and the level in the tank became too low for the pick-up tube.  This is not the case here.  Plenty of gasoline in the tank.
I came to another similar hill.  Same thing happened.  I tried pulling out the choke a little bit but it did not help.  It acted as if there was not enough gas in the bowl of the carburetor.
 I finally made it home (it was doubtful for a period of time).  I feel this is a fuel flow issue. I checked the fuel filter and it looked cleaner than I expected.  I checked and cleaned the carburetor jets, and they also looked fine.  I disconnected the fuel line to the carburetor, connected a clear hose to the line, and ran it into a glass jar.  I then manually operated the hand lever on the fuel pump.  If I pumped it slowly, I got a reasonable amount of fuel.  However, if I pumped it quickly, the volume looked to be much less.  My bigger concern is that, even when pumped slowly, there were a lot of air bubbles that I could see in the clear tubing that I connected.  Has anyone done anything similar?  Should there be any air in the fuel line at all?  I would think minimal if any. 
Maybe I have a crack/leak in the pump diaphragm, or maybe an air leak in the filter/valve control assembly?  It has been a few years since I rebuilt the fuel pump, so I just ordered a new rebuild kit.  While waiting for it to arrive, I may try to connect a clear line on the other side of the fuel pump to see if there is air entering the fuel pump.  Might help to isolate what is going on, if this is even the root of the problem?  I just don't know for certain.
Since the engine is running fine on level ground, and short hard acceleration is also ok, I think my ignition timing is ok.  I keep coming back to suspecting a fuel delivery problem, but I would welcome any additional "constructive" comments and advice.

Thanks for your time!

Was it too steep hill? Could it be that the carburetor was inclined and the carb float closed the fuel line?

Scott Montoney:
I doubt it.  I travel this route with her several times a week, during the spring to fall seasons.
But I greatly appreciate the input.

Hello Scott

If I take the goods elements concerning your fantastic vehicle correctly, it must be equipped with the M180 engine. I / 180.920

Your actual issue is strangely like a fuel pump problem
According to what you announce as a problem, I would lean more towards a membrane problem than towards another known phenomenon which is that of excess pressure (which is corrected using shims of thickness ... but this  is not the subject)

As you know probably, in the workshop manual,  it is recommended, before dismantling the pump, to make sure :
that the suction height is at least 0.9 m (what will be called vacuum)
that the discharge reaches at least a value between 0.25 to 0.3 kg / cm2

Do you have the technical means to check these values (depressiometer / manometer) ?

Courage , take care and stay safe !!!

A little additional information just for the knowledge ,
you can also control in addition the flow rate of your fuel feed pump which must be established between 35 and 40 liters / hour at the speed engine of 5 000 rpm ( I dont like this speed for an Oldie .. but its an MB procÚdure )
In fact
0.58 Liters to 0.66 liters  / 1 minute
0.29 liters to 0.33 liters / 30 seconds 
But normally for doing that control you need a bench test...


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