Q: I have a 1990 jeep cherokee larado. for the past 2 weeks or so, its taken longer to start, now, it will try to start for about 3 seconds then shut down. i switched the relays around, i cant hear the fuel pump turn on anymore. were's the fuel pump fuse? or is it just a relay under the hood? the only other fuses i know about are under the drivers side dash. i didnt see a fuel pump fuse.....is there more somewere else i havent found??
A: Check the electrical feed to the pump when you first turn the key on. You should have voltage. Jumper power to the pump directly, it should run and stop when pressure is up. Computer driven fuel injection systems have overrides to prevent the pump from running when a critical sensor won't give valid readings. This can confuse the issue whether the pump is working or not. Often, a bad crank, cam or manifold sensor is actually the culprit.