Volkswagen Repair: 78 vw van fuel filter, bosch fuel injection, shotgun method

Question
Just bought a '78 vw 231 van. It didn't run for 2 years. Seller told me that the tank had been flushed but he had to replace the fuel filter a couple of times. I'm now having the same problem.
1. Where would I find the fuel filter exactly?
2. Are there other steps I should be taking?
3. Can you recommend a good users manual or repair guide? I currently have the Haynes manual but find it a bit vague.

Thank you in advance,

John

Answer
John, Thank you for your question.  I had this happen on a Type 4fastback and I finally had to use the “shotgun” method.
Replace: 1. fuel filter (located under the gas tank)
      2. fuel line
      3. all four injectors
               4. You can keep the fuel pump if it is still good.  MARK each of the ports.
The best manual is the Bentley manual for Type 2 1968-1979.  plus Bosch Fuel injection & engine management manual.
Hope that helps