Although the bubbler continued to work, my oil derrick pump stopped pumping. After removing the diecast engine cover, I saw a very simple circuit (I know just enough about electronics to get me in trouble). There were a few diodes, resistors, an 8v voltage regulator, some capacitors and a 555 timer. I felt the most "fragile" component was the 555 timer and since it's directly responsible for "timing" things, like the intervals of a pump, I made it my prime target.
The 555 timers are a popular component for all sorts of beginner electronic kits so I had a few in my electronic parts drawer, and I installed it in place of the original. Bingo! Although it pumps at aslightly faster pace, the pump is pumping again! This is a quick easy fix if you're handy with a soldering iron - the 555 timers can be purchased online - A 30/pk on Amazon costs under $7, buying just a 2pk will cost you about $3.00ea (23-APR-2021). You can purchase a new Circuit board from Lionel (part# 6002305045) for around $12 bucks or so + shipping. Since I already had the timer, this repair was more about convenience than money saving for me.