non starter

I have a tuscon deisel that will not start, it will turn over and almost starts, had a mate check
that there is fuel getting through, by removing fuel pipe etc from the filter to the injectors, he seems to think that not enough fuel is coming from the pumps in the tank! possible cause
of debris in the tank or waxing of the fuel around the filter gauze, (his comments also are use
of supermarket fuels) , how easy is to get the pumps out of the tank? have found the access
points for these under the rear seats , has anybody else had this prob?.