M1008 fuel filter/assembly question

[ssgtwright-usmc]

I bought a new fuel filter assembly for my M1008 since it was leaking and giving very poor fuel milage.
When I got it it did not have the vacuum/pressure switch to come with it.
From TM 9-2320-289-20P Fig 18 page 18-1 its listed as a pressure switch.
What does this switch actually do and how will the vehicle operate without it installed for the time being.
I have called many parts shops and they dont even know what I am trying to describe to them.
Its about the size of a quarter with a two wire connector at the other end.
Where abouts can I locate one and how much does it cost.
Ive even tried a google search with the part number but to no avail.
Thanks.

 

[JAsher45]

the reason you can not find that on the civilian side is because it is just a sensor for the STE-ICE. you do not need it. there are plenty of extra sensors and sending units that are only there for vehicle diagnostics. i did some scratching of my head when i went to replace my filter housing... i just went with a Racor spin on unit with fuel heater and water in fuel sensor.. the pig tails where easy to change to make it plug and play