I have changed the rear differential on my van and after that I went to start and it would not start I did not hear the fuel pump come on so I changed the fuel pump but the van will not start the fuses are good and the relays are good what can be the problem way the van wont start?

SOURCE: 1988 F150 wont start

Check the positive side of the battery for a burnt fusible link. It looks like a wire but when it's over loaded if burns in half. Look at the pos. battery side of the starter solonoid you'll see a few of them there. Check your ignition module as well. This controls the coil and distributor and is mounted to the driver side inner fender.

SOURCE: 1999 F 250 crank but wont start

look on injector pump make sure there are no loose wires

SOURCE: ford explorer eec relay

Try a new relay first. This may not be good news if that does not work. If you can find the EEC (computer) and unplug it, then replace the fuse-if it blows you have another cheaper part on the circuit thats bad.
If the fuse does not blow, then the EEC must be shorted.
If you have to replace the EEC you may find a kindly dealer with a cash-for-clunker sitting there to violate. Salvage yards have them, Ebay sells them. I have seen them at swap meets for $20. They are a high price part even rebuilt at Dealers or autoparts stores.