Suzuki Repair: car jerks dramatically, spark plug wires, bus mechanic

Question
My little 1992 suzuki swift  (3cyl...3 door) hates long distance driving. Every time we travel out of the city she start this horrid jerking.  Have changed spark plugs cleaned air filter, tried to find fuel filter but can't. In town there is no problem at all. I don't lose power as such, if I push in the clutch she'll pick up again - and some times this is what saves me from getting another car up my backside- When I took her in for her service nothing happened and the mechanic could only assume it is the petrol pump. maybe it is ,but if I stop on the side of the road for awhile she will go again with no problem.Its becoming annoying as I have to travel to work each morning at 5am and its a 60klm distance each way. However of an afternoon on the way home she doesn't always do it. That's at 4pm any assistance will be used and gratefully appreciated.

Answer
It may in fact be the fuel pump (yank terminology).  The best way to settle what's at fault is the following:   If the jerking starts immediately upon depressing the pedal to the floorboards, it's most likely in the ignition system (distributor cap, rotor, spark plug wires (cables?)
If it takes a few seconds, then the pump is more likely.
Sorry about the delay, I'm a school bus mechanic, and got to go with the students on a whitewater rafting trip on the Green and Colorado Rivers in Utah.  Very pretty, also very difficult, and impressive (I believe my adrenal glands have been tested repeatedly, and are working well)