Porter cable router turning off intermittently during job

The little compressors were not built for continuous duty. The pump probably seized, or the motor burned up, or both.

You probably have a bad cord. Try moving the cord around with the router turned on and see if the power cuts in and out.

Pressure switch - replace as soon as possible
Overpressure would be possible in that tank - it is dangerous !

Have you tried taking out the collet and cleaning it and the cavity where it goes? If there is any wood dust present it may be causing the problem. If that doesn't fix it, you may need a new collet.

right where it goes into the tank there is a oneway valve that is stuck or bad and needs replace

I think I may found have what you need. Here you go my friend:
http://www.ereplacementparts.com/porter-cable-75182-type-variable-speed-router-motor-parts-c-129_1672_12325.html?osCsid=banu8b4d4i426oqllnph0doi00

have you checked the motor reset
will be on the motor

Sounds like the pressure switch is shorted together. Unwire the switch and see if it shuts off.

Use a 45 degree 1/4'' shank router bit with bearing and adjust cut depth to desired depth. you may want to do a test cut on a scrap piece to make adjustments before you make the intended cut.

This may not be related to your jig. It may be movement in the vertical axis resulting from:

1. The router bearings being worn allowing the bit to move up and down.
2. The router bearings worn allowing the spindle to deflect side to side which changes the bit height slightly (cuts on the edges, making the cut a hair deeper).
3. The router collet or router spindle worn, allowing the bit to move during cuts.
4. The jig guide plate deflecting or no longer flat.
5. Excess vibration in the router causing the wood to move in the jig.

To check the bearings; try routing the cut with a straight bit first to clear the wood for the dovetail bit. Then cut with the dovetail bit (a new one preferably) using very light feed pressure. Is the joint tighter? If so then the bearings are worn. Have the router serviced or replace it.

Check the end-play by pulling on the router shaft, does it wiggle slightly in and out? If so this is your problem. Have the router serviced or replace it.

Be sure the wood is flat and the faces planed parallel, if they aren't the dovetail line will be straight but when you assemble there will be slight end gaps in sections of the dovetail.