Engine loss of power going up steep hill.

[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!
Scott

[Ted]

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.

[Marc1340]

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)
And
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 !!!

[Marc1340]

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 procédure )
In fact
0.58 Liters to 0.66 liters  / 1 minute
or
0.29 liters to 0.33 liters / 30 seconds 
But normally for doing that control you need a bench test...

[Scott Montoney]

Thank you!
Yes, engine is 180.920.
As a matter of fact, I had checked the Workshop Manual just this morning and made the checks you mentioned.
My test tool is a dial gauge that reads vacuum and pressure.
I tested on the car, with starter, and off the car with the hand lever.
According to the scales on my gauge, the Output/Pressure was only at .1 kg/cm2.
The Vacuum/Intake was at 23 cm Hg.  (.23 m).
I have ordered a rebuild kit from Niemoeller.
I will also verify the mechanical clearance of the pushrod/cam as specified in shop manual.
I have a hand vacuum pump.  I connected it to my vacuum/pressure gauge and the vacuum readings of each tool do match, so I believe the readings of the tool are fairly accurate.

Thanks again.

[Marc1340]

Good evening Scott

Excuse me for pointing you to this problem when you identified it yourself.
According to the values that you noted, indeed the membrane seems a little tired.
By acquired and although I do not know the history of your beautiful car, would there not be a hold under the supply pump ? ( to reduce the pressure ...) you never know ...

As purely friendly advice, (don't see any mischief), I allow myself to recommend to you (I do this for the oldies I frequent at home), the mounting of an electronic ignition (+ Coil + amplifier) as well that the installation of an electric gasoline booster pump.
So equipped your beauty will never let you down
I also read these recommendations on our sister site 170.DE

Stay safe and take care
Best regrds
Marc

[Scott Montoney]

Yes, I've considered those "upgrades", and have explored various ways to do it without altering the look of the original parts.
However, she is still running on original design parts, and has over 560,000km. 
On the other hand, I do take her on long trips from time to time, and I do need reliability as well.  I carry a good supply of tools and parts in the trunk.

[Marc1340]

Hello Scott
I share your point of view on keeping the original elements at all costs.
After this first thought, it quickly comes to mind that you can drive quietly without reserving half of your trunk for the  toolbox, not to mention the sympathetic thoughts of your wife when you are on the side of the road broken down ... .
For my part I am ready for many sacrifices not to hear it during 560,000 kms !!! not you?
Maybe it's because you don't know my wife ....

The electronic ignition system's in 6 V for example are of a very beautiful aspect in conformity with the original, ditto for the coil, the sight of the engine is not spoiled and especially it is about a reversible operation

The assemblies of an electric fuel pump (always in 6 v) are done in a discreet way and also reversible if necessary ...

Have a nice day

[Scott Montoney]

The fuel pump has been rebuilt, and road testing indicates that all is well again.
The volume of fuel looks to be much increased, and a bit higher pressure as well.
The only thing I could identify as the probable issue was that the two rubber valves inside the pump were quite hard compared to the new ones.  Probably not providing a good seal.

I'm considering a modification, but will discuss it in a new post once I dig into the details.

Thanks
Scott