Shaken, but not stirred
QI have bought a CAV agglomerator for the Isuzu 42 engine on my boat. I assume that fitting it near or below the bottom of the fuel tank would avoid priming problems. But is it better mounted on the boat structure near the fuel tap or on the same engine mounting as the fuel filter? Is there is anything else I should consider about the installation?
ROGER CREWS, via email
ATONY REPLIES: Firstly, an agglomerator is a filter. Normally the engine filter is used as the agglomerator and the extra ‘inline’ unit is a sedimentor. The pores in filters must present a degree of restriction to fuel flow; by contrast a sedimentor uses an inverted cone to centrifuge the larger droplets of water and dirt from the fuel, with perhaps a 2mm gap around the cone, so it presents no resistance to fuel flow. Apart from that, the parts of the CAV agglomerators and sedimentors are common to both.
Your unit has a metal bowl, so with no danger of glass breaking, the risk of fitting it low down is not great. A misfitted seal could start to leak, so I would fit it higher up so less diesel can leak into the bilge, but ensure the bottom of the agglomerator is below the fuel level when the tank is close to full.
An engine running well should not shake too much, but if it starts misfiring it really will shake about, so I would mount a sedimentor or an agglomerator to the hull rather than engine.