intermittent probs

car : 1986 polo gl

seems to run ok, then well, then badly, then cuts out.

manage to get it started after a while.

replaced the usual stuff ie distributor cap, rotor arm, fuel pump.

had someone out to look at it and says that the fuel pump isn't pulling much fuel (where the fuel filter is there is a constant pulsing of not much fuel. normal? or should there be a much greater amount of fuel, say 1/2 the seethrough cap full if that makes any sense).

anyway my mechanic thinks it may be a fuel push rod problem which is causing the pump to be less efficient then it should be. is this a known issue?