'92 Dakota won't start

Have a '92 Dakota w/ 3.9L that will crank fine but not start. Just went out one day and "no fire in the hole" -- no trouble of this kind before. Tried replacing coil, wire, rotor, distributor cap, wires, and plugs. Also read in forums that a power wire splice about 12" under fuse box can corrode and go bad -- had that all apart yesterday and harness looks excellent. Get fuel pump "hum" at ignition on. There's a spark when plug pulled, but not sure it looks good -- like to see a nice blue "snap" --but again new plugs and coil -- so I'm just not sure. I tried ether to see if it could be fuel-related, but still no fire in the hole. So you see my problem! -- it appears I have spark, and fuel (ether) -- and it seems to me if you have spark and fuel it oughta go! Could it be timing?? I have had an intermittent problem in the past with it not wanting to shift into high gear (even before lockup), and at that time got a "vehicle speed sensor" fault from ECM (not sure, but assumed that was the problem), but now even that is gone (get the "55" flash code). Also have read about Auto Shutdown Relay and Crank Sensor, haven't tried those yet, but I'm thinking I wouldn't be seeing spark if those were the problem. Any ideas??? Thanks much! -- Pete

Your are right about the crank sensor, if you see spark, that sensor isn't working. The same goes for the auto shutdown relay, it supplies power to the injectors, fuel pump and coil. But see if you have adequete fuel pressure by hooking up a pressure gauge on the fuel rail for the fuel injectors. If you have at least 39 psi, you're in good shape. If not, you could have a weak pump, clogged injectors or even a restriction somewhere in the fuel system.