While the new era of Formula One roared back into life at Circuit de Catalunya, Alonso was forced to watch the opening morning from the sidelines.
McLaren, who have won 12 drivers' championships and eight constructors' titles, are desperate to return to the front of the grid.
But Alonso, the double world champion who is out of contract with McLaren at the end of the year, managed just one tour of the Barcelona circuit.
McLaren are unsure whether they will be able to fix the problem before the day's action concludes.
"We have an oil systems issue which requires a full investigation," a spokesperson for their engine supplier Honda said.
"We plan to run again today, but due to the difficult access location it will take several hours to resolve."
Red Bull, who unveiled their new car on Sunday, also hit trouble on the opening morning in Spain.
Daniel Ricciardo completed only a handful of laps before his car stopped on track at turn four.
The Australian hitched a lift to the pit lane while his Red Bull was towed to the garage on the back of a pick-up truck.
There were no such concerns for Mercedes, however, with new driver Valtteri Bottas setting the fastest time and completing more laps than any other driver.
The Finn, who has replaced world champion Nico Rosberg following the German's retirement, posted a best lap of one minute and 23.370 seconds.
His time was marginally faster than Ferrari's Sebastian Vettel.
Lewis Hamilton will get his first proper taste of the car he hopes will fire him to a fourth world title when he takes over testing duties from Bottas later on Monday.
