I just bought a 1978 300d 1 month ago... I have been running a blend of wvo and rug. It has been running great... I noticed the primary filter getting pretty dirty and the power was failing.. I changed both filters and by the next day there wew large peices in the primary.. I changed both filters again... I let it sit and idle a while then it died. It restarts but shakes, etc then dies. I tried to back feed the libe with compressed air to free up anything on the strainer... Doesn't seem to help... Can it be air in the line? Should I pull the tamk and clean? Injection pump shot? Hope to hear from someone! Thanks.. Marc