Mercedes technical chief Paddy Lowe says the operation is working "day and night" in order to fix the issues which have plagued Lewis Hamilton across recent races.
Hamilton suffered an MGU-H failure during qualifying for the Chinese Grand Prix, which left the reigning World Champion at the back of the grid, from where he recovered to seventh.
The problem struck once more following Q2 in Russia, leaving Hamilton in 10th place, before the Briton went on to finish the race as runner-up to Mercedes team-mate Nico Rosberg.
"The highest priority is to come back with our MGU-H problem solved, having had a repeat fault over the past two race weekends," said Lowe ahead of the Spanish Grand Prix.
"The team has been working day and night to understand it and we're targeting a clean weekend all round."
Mercedes boss Toto Wolff added that the problems are a result of Mercedes continuing to push the limits in order to maintain its advantage at the head of the pack.
"The longer regulations remain stable, the harder it is to find extra performance," he said.
"We are pushing the limits to ensure we remain competitive - but if you push the limits then at a certain stage you risk stepping over them.
"The whole team, on both the chassis and Power Unit side, is working flat out to extract every millisecond from our package without compromising reliability.
"This is a group of great engineers and I have no doubt that they are going to achieve that."