It'* not equal. You need to change that fitting to match the TEE. Or get another gauge.

ughh headaches, so the problem lies in the fact that my pressure sender is 1/8 npt. Everything else is a flare fitting but the 4an to 1/8 npt adapter.

Although not as user friendly as –AN, you should be fine using NPT connections for this application. The majority of fuel pressure gauges and senders out there are NPT.
A lot of the aftermarket fuel pressure regulators with –AN line connections still have NPT gauge ports. There are also regulators out there (like those 100 psi Mallory adjustable regulators IIRC) that have NPT line connections.
In general the flare fittings are best used for fuel line connections (flare fitting hose ends are easier to install and less bulky than NPT hose ends).

To make NPT connections I first make sure threads on both parts are clean and free of defects and then wrap 2~3 layers of Teflon tape tight and neat around the male part. To test for leaks, run the fuel pump to bring it up to pressure without starting car and let it sit for a while.

NPT fittings on gauges are typically for two reasons:

1. It'* not an installed-always application. Use the gauge, then takeit off.

2. If it'* left, it'* for a carbureted application with far lower fuel pressure than what fuel-injected cars use.


My gauge has a flare fitting because it was designed to be left in at all times and was also designed for the higher pressure of fuel-injected applications.

What'* the size of the threads on that T? I'm looking to hook up the same gauge in my car but using a AN line.

Ed