I've swapped out both fuel filters on my 83' 300D and my engine is not happy.

Initially, it was airlocked so I bled the fuel system but even so, the engine shakes, sputters and kicks out exhaust but won't properly start up. After about 30 minutes of intermittent cranking (15s max) it's now cranking very slowly until it eventually dies out. I figured I'd drained the battery so I had a neighbour come give me a jump and even with that it's still slow.

Has anyone dealt with this before? Open to any and all recommendations before I tow it to the shop.

Thanks,