4.0 swap electrical question

Ok I am learning electrical and am not as knowledgable as I wish. Problem is after dash and harness swap I am not getting power to the inertia switch so no power to the fuel pumps. Power to dist box and through fuse there, but not to green wire at switch? Is it the relay? How do you check a relay? Both pumps are new and work fine when powered. Any ideas?

Fuel pump(s) power runs like this:

Battery------Fuse(or fusible link)-----Fuel Pump Relay--------inertia switch--------Pump(s)----Ground

Fuel pump Rely works like this:

Battery-----Fuse(or fusible link)----EEC relay----Fuel pump relay-----Computer----Ground

When you turn on the key the EEC relay should close and send power to EEC(computer), Fuel injectors, Spark system, and fuel pump relay

But fuel pump relay doesn't close because it has no Ground, computer controls that to turn fuel pumps on and off.
The computer WILL ground the fuel pump relay for 2 seconds each time key is turned on, but only for 2 seconds, computer will not turn it on again until engine RPMs are above 500(engine started), this is a safety measure to prevent fuel from being pumped out if fuel line should break, broken fuel line means engine stalls so fuel pump would shut down.

So if you are testing for power(12volts) at inertia switch it will only be there for 2 seconds when key is first turn on, but you can turn it off and on again, it won't hurt anything.

If you want to test relay you can use the VIP(OBD1) connector in the engine compartment, usually by the power brake booster.
Look here: http://www.therangerstation.com/tech_library/OBD_I.shtml

Second picture down has the Fuel Pump slot IDed
That slot is connected to the computers Ground wire for the Fuel Pump relay, so if you Ground that slot fuel pump will come on if key is on.
Turn on the key then ground that slot with jumper wire, you should hear relay "click" and fuel pumps will come on.
If not then time to check fuel pump relay socket
Pull out the relay(green base)
Key is off
Test each slot for 12volts, there should be 1 slot with 12volts, thats the fuel pump power from battery via fuse, no power = blown fuse
Turn key on
Check for 12v again there should be a new slot with 12v now, full 12v, that is from the EEC relay, if no 12v then check wiring under socket.
EEC relay also has a fuse, so if no 12v then that fuse could be blown.

Fuse or fusible link.
A fusible link is a short color coded wire, it was used as a fuse on many circuits in older cars and trucks, you will find them connected to Starter Relay post with Positive Battery cable, fusible link can be 3" to 6" long, it is designed to separate(blow) without melting or causing a fire, so just check for separated wire coming off the starter relay post.

Right on, thank you for such a detailed answer! I learned that while jumping things. At first I would turn key on then test and as you explained nada after 2 seconds so now I completely understand the system and I will hook it all up and fire up my rebuilt 4.0 this weekend. God willing I will be very close to completing my long dreamed of Bronco. Thanks soo much for your time!

I'm probably to late but when I did this on my 93 to 86 swap the fuel pump wouldn't work after motor dash swap.While I could see the right colored wire in the steering column for the fuel pump asked a body shop friend he said some were made to turn on the flashers on impact.I went ahead and put the 93 steering column in everything plugged together nicely with the dash and fuel pump worked great after that.

I had this problem too. Mine was caused by the harnesses sitting and the connections getting crappy. As I was chasing the problem I was unplugging things, and after undoing the connector under the fuse block and putting it back together things started working.