1. You will get more response in the Diesel area.
2. You have added "also put a 12 volt fuel pump in line after the main filter" ... Why? I assume you use the term 'after' to discribe 'downstream' and that you have a pump installed between the canister filter and the IP? That is not common practice. Some folk, using an alternative fuel, place a 'faucet' style pump downstream from the fuel tank outlet.
Is the clear pre-filter black or has black spots? This is alge growth and your strainer may be plugged.
Have you verified the fuel supply? This test takes 10 minutes if you have car ramps or a handy curb. Try jacking up the rear of the car (or use a curb), crawl under with a screwdriver, rag (you will loose some fuel), safety glasses and the largest pail that will fit, remove the fuel line on the pass. side of the differential and verify flow and quality of fuel. You should get a steady, roughly 1/4"-3/8" stream of clear fuel. If not, your in-tank fuel strainer may be plugged. If plugged: some folk have reversed the fuel lines in the engine compartment ... swaping the return line for the output line, drain tank and use biocide or gassoline to flush the tank, remove tank and flush. I would rather fix the strainer/fuel problem.
If you have installed an additional fuel pump as I discribed, try removing this pump, use a temporary fuel tank (used, clean, plastic bottle) installed up stream of the pre-filter (clear, small, plastic filter) prime and see if the engine runs. If engine runs, you have a leak in the fuel line between the prefilter and the tank (assuming the additional pump issue has been corrected).
3. Primming: I have a 79 300 SD and after replacing a failed OEM primer, had to crack the IP to nozzle nuts 1/2 turn and crank the engine over till fuel leaked from all nuts. I had to turn the engine over way more times than I thought needed. Some manuals (notably the !@$##!@@! Haynes ) stated cracking the banjoe bolt nut on the canister filter housing to manualy prime. This is bunk. The canister filter housing has an air bleeder hole (at least on the MB's I've worked on).
3. You may have a leak in the fuel line allowing air to block fuel flow. Verify fuel flow using the IP to nozzle line nuts. This will test every part of the fuel system except the nozzles and IP timming ... lines, filters, pump, etc.
4. Test the fuel that leaks from the IP to nozzle nuts for diesel smell. Someone may have added water to your fuel & or your alternative fuel process is faulty.

Good Luck. You should be on the road soon and with out the tow $ it took for my education!