W123 1983 Losing speed while going uphill on motorway

[W123 200]

Hi there,

A couple of months back, i started experiencing loss of speed while going uphill on motorways. Since then I have changed the spark plugs, cleant the carb, and changed the fuel hose - but the problem still persists. I would really appreciate any suggestions you may have? thanks. (its a 1983 2.0 Petrol)

 

[gtvlusso]

Go downhill more often....?! Sorry - could not resist.

Torque convertor issue? Assume gearbox is downchanging?

 

[Stratman]

It's clearly down on power, so start there. The best thing you can do is a compression test on the engine. Without good compression it'll never make the power it's meant to. Assuming the compression is good on all cylinders, check all the peripherals. Air filter, distributor (including cap and rotor), check for air leaks around the inlet manifold. Is the carberrytooter float level correct? What colour is the spark plug insulator?
If all that fails to reveal the cause make sure the brakes aren't binding.

 

[grober]

You might also want to check the fuel pump output and that fuel tank is venting properly

 

[jaymanek]

I would definately say this is a fuelling issue...
The car models dont have an electric fuel pump, only a manual one stuck to the side of the engine... worth looking at that and the carb setup.

 

[W123 200]

Thanks for all the tips!! the engine keeps stuttering if I am doing 70mph on a uphill and then reduces to 40-50mph. I live in the alps its a pain trying to avoid the motorways and only using rural roads

 

[Stratman]

Ahh! The 'stuttering' description would point to lack of fuel, as has been mentioned already. The next time it happens pull over quickly and remove the fuel filler cap. Do you hear a rush of air, or even the tank unbuckling? If so, the tank venting system is blocked. It could be as simple as a rubber tube has become blocked with mud.