Metering unit Outlet Union for numbers one, three, four and six outlet pipes sold on an exchange basis. This is the early type used up to engine number CP75314 and uses a Dowty type seal. As new parts are currently unavailable please use this exchange part 518629EX or second hand part 518629SH.

This part must not be confused with the later part 521029 fitted from CP75315 which uses a ring and a plain seal. If the unions (which house the non return valve) are used with the incorrect sealing method there will be serious consequences.  

 

If the early union is used with the later seal and ring, the ring will not be located properly and the seal will not seal resulting massive fuel leakage.

If the later union is used with the early Dowty seal, the nose of the union will not seal properly in the 'doughnut ' or 'bung' seal in the metering unit causing over-fuelling by the addition of un-metered fuel to the metered charge.

To assist with identifying the correct the parts please see the photo of the parts laid out  for comparison.

Whilst fitting this part it is usual to change the bung seals RTR4077 too.