If Buster offers advice. Take it to the bank. He knows his stuff. I can't be sure on a 1994 Rodeo, but some Isuzus had a circuit in the alternator that powered up the fuel pump relay. if the alternator isn't charging (10.3 volts), this circuit isn't powering up the fuel pump. The pump is temporarily powered up when you crank the engine. AGAIN, I'm not totally sure on your application, but this was the story on the 2.6 models.
Another thing, unlikely because you are talking idle speeds, but I had a 94 Trooper (same engine) and mine wasn't charging under load and cruising speed. Load being A/C on and headlights on. The load against the alternator was causing the outer ring of the harmonic balancer to slip. The outer ring had the pulley grooves in it. Harmonic balancers for this vintage Isuzu 3.2s were notorious for failing.
I would find and check all fusible links as well. Dennis
Another thing, unlikely because you are talking idle speeds, but I had a 94 Trooper (same engine) and mine wasn't charging under load and cruising speed. Load being A/C on and headlights on. The load against the alternator was causing the outer ring of the harmonic balancer to slip. The outer ring had the pulley grooves in it. Harmonic balancers for this vintage Isuzu 3.2s were notorious for failing.
I would find and check all fusible links as well. Dennis
