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Beitrag begonnen von twigren am 02.02.2020 um 14:02:18

Titel: Engine problem (very very weak, under load...)
Beitrag von twigren am 02.02.2020 um 14:02:18

Dear friends,

I have been struggling with various engine problems the past time.
Basically everything under the hood has been gone through, in detail.
Several issues have been worked with and components have been renovated/replaced.

The engine now starts perfectly and runs smoothly, on IDLE (!).
Responding quite fine as well as the accelerator/throttle kicks more fuel in.

However, when put into gear and load increase, the behavior is very strange.
It's extremely weak, coughs and when load increase more it dies.  
Starting things up again, engine starts directly but the problem repeats as soon as the smallest load is added..

I have checked:
- Ignition timing (calibrated based on UDC and checked by strobe-light on cyl #1).
- Breaker contact (measured. But as things runs smoothly on idle it cannot be an issue)
- Coil (as it works on idle it cant be poor. Resistance measures are also OK)
- Compression (which shows more or less exact the same numbers for all cylinders)
- Mixture screw, on carburetor (2 to 2.5 laps unscrewed versus the "dead mode")
- New spark splugs
- Wires checked and absolutely no issues.

In regards to the spark plugs, there is obviously a problem as they (all four) turn very black/grimed)
I'm using a new set of NGK B6HS., as recommended by another 170 owner.

So, the question remains - How can the calibration for idle-run be so perfect, but at the same time so bad when load is added?
Obviously I am missing something out here... ?!

Thanks in advance!!

Titel: Re: Engine problem (very very weak, under load...)
Beitrag von robi64 am 08.02.2020 um 13:31:39

Hi there.
You could perhaps take off the air filter at short notice
to see how it behaves when the mixture is a little lean.
Just as an idea.

LG Rolf

Titel: Re: Engine problem (very very weak, under load...)
Beitrag von bened am 09.02.2020 um 16:38:34

Hi Thomas,

nearly got the same Problem you have. Can you do full throttle when car is in neutral ?
You can check the small tube in the carburator. If you have a look from the top into the carburator, you can see that 3 mm thick curved tube. if you open the throttle by Hand (engine off!). You should see that there is a short Splash of fuel into the carburator.
Can you verify this?
IF you have skype you can also add me for short Chat. (write me a PM)

Titel: Re: Engine problem (very very weak, under load...)
Beitrag von nitrolack am 21.03.2020 um 14:02:52

Hi Thomas,

did you already solve the problem ?
Looks like ignition problem to me. Weak spark.
I had the same with an old motorcycle. It idled perfectly but died under load.
I my case it was the condensator, although looked  like new.
Could be also shortcut in breaker points or the coil.


Titel: Re: Engine problem (very very weak, under load...)
Beitrag von James Allen am 21.03.2020 um 17:12:25

Check the fuel pump and lines for restrictions.  Check the fuel. if it has sat in the tank for a long period, get rid of it.

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