how to test for return blockages
 

I've been suspecting of some blockage in the return circuit (probably in the swirl pot) so i decided on an unusual test.

Decided to measure warm / cold, system / control pressures using the "normal" return circuit vs a hose straight to a jerrycan.

The only difference found was regarding the system pressure: to the tank i got 4.8, to the jerrycan i got 4.5

What do you think ? seems a small blockage exists, i will probably remove the tank.

Bump

I would not worry about that difference. You have to realize that there is more restriction pumping back to the tank than the jerrycan due to the length, bends, diameter of the lines, and back pressure of pumping into a small whirl pot with fuel in it as opposed to the short distance and lack of back pressure to the jerrycan. I would expect more of a pressure difference than .2 bar (3psi) if there was a serious restriction.

Yes, good point.
I was also unsure about the small .2 difference.

Just make sure the return line to the swirl pot doesn't have any debris which causes an intermittent blockage like my 1977 had. Some rust flakes and rubber shavings.

d/c the line and blow it out.