Tesla Inc.’s tumultuous year has fueled concern among some of its suppliers about the auto maker’s financial strength after production of the Model 3 car drained some of its cash, according to industry executives and documents.

A recent survey sent privately by a well-regarded automotive supplier association to top executives found that 18 of 22 respondents believe that Tesla is now a financial risk to their companies, according to the document reviewed by The Wall Street Journal.

Separately,...