N

N91CZ

Well Known Member
Does anyone know what thread is used in the Lycoming fuel pump inlet and outlet ports. I know adapters are avaiable for ACS adn the like, but I am looking to add a Tee at the outlet. I am guessing it is a straight thread 9/16-18 or similar.
 
If you're talking about the female threads in the fuel pump body, I recall they're 1/4"npt ... but somebody should confirm that.
 
fittings

The AC style fuel pumps are straight thread. The thread is the same as an AN4 firewall fitting. Fitting requires an o ring and jam nut. Pitts uses AN firewall fitting, some manufacturers use special fittings that are not AN.
 
Engine driven pump fitting

#6 O-ring thread. The thread is 9/16-18 UNF. Use a #6 fitting for an O-ring boss. AN or JIC will work. If a straight fitting can be used, then a AN815-6 will work with a O-ring on the end that screws into the pump.

Don
 
ACS sells one of those fittings that have a "T" - for specialized fittigns, they are surprisingly inexpensive, and if there is one place you don't want a fuel leak, it is right there. I have seen fuel pump inlet/outlet fittigns jury-rigged and leaking, and with eh "right" fittings so affordable, that is a a shame...
 
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