Terrano II Drawing Problem

Good morning and greetings to the entire forum. I enter my first rare problem. I have a terrain II TDI 2.7 of 96 and has gone from 300 thousand kms. It has a problem that has gone progressively.
The car rolls very well but occasionally, that is, when you want, stop in a stop or traffic light, putting first and giving gas right at that time the cala car. This only happens and only when stopping and putting first or back and right when giving some gas.
Sometimes he doesn't, sometimes yes.
When he would go, I must expect a few moments to start again. If I do it right away, it does not start.
The mechanics are crazy with the problem and attribute the problem to the injection pump, but before changing it I would like to know if someone has had this problem and could be something easier to repair.
Thank you so much