Fuel manifold assembly
 

A buddy of mine just bought an 06 f250. Well his wife called him and said his water n fuel light was on. So he told her to take it to the shop and have the oil changed and all the filters. Well she called him back and said the dealer said it was the fuel manifold assembly that was bad. My ? Is WTH is a fuel manifold assembly.

The HFCM is what they are probably referring to, has the fuel pump, the water separator and main filter and the water drain. If it was me, I'd crawl under the truck, use the single allen wrench it takes to drain the water separator, and see what happens. That's insane.

x2 Drain the water out and viola