  We investigate the X-ray origin in FR Is using the radio, submillimetre,
optical, and {\em Chandra} X-ray data of a small sample consisting of eight FR
I sources. These sources are very dim, with X-ray luminosities $L_{\rm
X}/L_{\rm Edd} \sim 10^{-4}-10^{-8}$ ($L_{\rm X}$ is the X-ray luminosity
between 2-10 keV). We try to fit the multiwaveband spectrum using a coupled
accretion-jet model. In this model, the accretion flow is described by an
advection-dominated accretion flow (ADAF) while in the innermost region of ADAF
a fraction of accretion flow is transferred into the vertical direction and
forms a jet. We find that X-ray emission in the source with the highest $L_{\rm
X}$ ($\sim 1.8 \times 10^{-4}L_{\rm Edd}$) is from the ADAF. The results for
the four sources with moderate $L_{\rm X}$ ($\sim$ several $\times
10^{-6}L_{\rm Edd}$) are complicated. Two are mainly from the ADAFs, one from
the jet, and the other from the sum of the jet and ADAF. The X-ray emission in
the three least luminous sources ($L_{\rm X} \lesssim 1.0\times 10^{-6}L_{\rm
Edd}$) is dominated by the jet although for one source it can also be
interpreted by the ADAF since the quality of X-ray data is low. We conclude
that these results roughly support the predictions of Yuan & Cui (2005) where
they predict that when the X-ray luminosity of the system is below a critical
value, the X-radiation will not be dominated by the emission from the ADAF any
longer, but by the jet. We also investigate the fuel supply in these sources.
We find that the accretion rates in four sources among the five in which we can
have good constraints to their accretion rates must be higher than the Bondi
rates. This implies that other fuel supply, such as the gas released by the
stellar population inside the Bondi radius, should be important.
