Tesla Inc.’s version of production “hell” apparently means the Silicon Valley electric-car maker will run low on cash later this year as it embarks on an ambitious plan to build its first automobile for mainstream consumers.

Chief Executive Elon Musk reiterated on Wednesday—after announcing a better-than-expected second-quarter loss—that the 14-year-old auto maker faces challenges in learning to manufacture the new Model 3 sedan at much higher volumes than previous vehicles.

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