  We run hydrodynamic simulations which follow the colliding winds structure of
the massive binary system HD 166734 along its binary orbit, and show that close
to periastron passage the secondary wind is suppressed and the secondary
accretes mass from the primary wind. The system consists two blue supergiants
with masses of $M_1 \approx 39.5 ~\rm{M_\odot}$ and $M_2 \approx 30.5
~\rm{M_\odot}$, on a $P \simeq 34.538 ~\rm{days}$ orbit with eccentricity of $e
\approx 0.618$. This close O-O binary with high eccentricity is observed
through its orbit in the X-rays, where it shows an unusual long minimum close
to periastron passage. We use advanced simulations with wind acceleration and
prescription treatment of accretion and simulate the entire orbit at high
resolution that captures the instabilities in the winds. We find that the
colliding wind structure is unstable even at apastron. As the stars approach
periastron passage the secondary wind is quenched by the primary wind and the
accretion onto the secondary begins. The accretion phase lasts for $\simeq 12
~\rm{days}$, and the amount of accreted mass per cycle we obtain is
$M_{\rm{acc}} \simeq 1.3 \cdot 10^{-8} ~\rm{M_\odot}$. The accretion phase can
account for the observed decline in X-ray emission from the system.
