You should be able to get an 8 meg SIMM for next to nothing these days so you could see if it's the memory.
Another thing to try is to clean the contacts on the motherboard where the accelerator connects, plus try cleaning the power supply connection (unplugging and replugging a dozen times or so should scrape off anything on the metal). If you have a multimeter, check the voltages from the floppy power connector to see if either is lower than it should be.
