I'm trying to diagnose a problem with a 97 rodeo. Won't start due to no fuel. If I jump the the relay I can hear the fuel pump working. But the ecumenical is not sending signal. When I measure the voltage on the 20 amp fuse for the fuel pump on the main fuse box.... the fuse signal is grounded. Where would the short be? Am I wrong to expect that there should be 20 amps of current ? Both the fuel pump fuse and the o2 fuse are grounded. Massumption is that since the polarity is reversed on that circuit, the ecu will not send pulse signal to the fuel rail. And the signal won't turn the relay on.
I've checked the wiring from the fuel pressure sending unit to the ecu. Where could the short be?

 

I am going thru this on my 97 rodeo. It turns out something happened between the alternator and the ECM that caused the fuse for the ECM to blow and not let the fuel pump run. I disconnected the wire on mine that goes from the ECM to the alternator, replaced the ECM 15 amp fuse and it now starts and runs.