Hummm... you're in a world of hurt.... If you're an electroncics geek you could trap the frequency of the RFI and drain it to ground... but that's a hassle.
If the problem is indeed RFI then your limitd to:
1. Moving the antenna.
2. Shielding the pump.
3. Making sure the coax cable is intact.
4. Making sure all the grounds are in good shape.
Have you hooked up a buddies radio to the antenna to see if the 2nd radio also is affected by the RFI? Does the RFI emit far enough to interfere with a 2nd radio on another Jeep? If the pump is emitting that much RFI it may be going south....