Are the windscreen washers "wind assisted"? When I use the washers when stationary a little water comes out but it does not even reach the windscreen. Do I have a bad pump/blocked tubes or is it working as designed?

 

might be a blocked jet, the chromed part that sits over the cowl.

 

The original washer pumps are very old and the squirt of water is not the greatest. Finding a replacement original Lucas pump is impossible so your choices are try and clean / rebuild your original Lucas pump or buy an after market new pump and place it in line but out of sight.
SNG do several aftermarket pumps but you might find them cheaper on e Bay or from a Kit car parts supplier.
https://www.sngbarratt.com/English/#...rnedDown=false

 

The original pump on the glass type reservoir wasn't great. I remember my father taking it apart when our car was about six years old. Later he fitted an inline pump in the pipe. That worked until a cold winter a decade later when the water froze and shattered the glass bottle (painful considering how much they cost now). In those days, Jaguar dealers stocked the plastic reservoir replacement - a genuine upgrade. It has a much better pump and has been on the car ever since. That said, the nozzles can still become stopped, but are fairly easy to clean.

Personally, I'd use distilled water to fill the windscreen washer reservoir (and everything else). It makes life easier in the end. Living in the Netherlands, you're likely to own a dehumidifier (or several); they're a good source of water for the car.

 

I have the original plastic reservoir. I have just taken the pump motor apart and cleaned everything.


Motor sounds much better now but still no real pressure.
I guess I will have to take the dash top off and try to remove the nozzles (tried a needle but didn't help), then replace the tubing.

Just tested it in the sink and the pump does a goes job, plenty of pressure.

 

You probably don't need to remove the dash top. As I recall, you can unscrew the nozzle from the scuttle fitting. Then it's possible to clean inside the jet and run the pump to flush out the rest of the system.

 

I have one each of the original containers with pumps in working condition. But the pumps are not very powerful, so I installed a modern generic pump in my S type, the kind sold in mail order catalogs from J.C. Whitney USA back in the 1970's, works great.

And do not fill container with Windshield Washer Fluid, it clogs the pump and jets and stains the paint. Fill only with water.
In winter, add a spoonful of alcohol to the container to prevent freezing, this is instructed in the Service Manual.