93 V6 Randomly Doesn't Start

[wbrown05]

I have a 93 V6 4X4 that intermittantly doesn't start. When it doesn't start it turns over fine it just doesn't fire. A mechanic replaced the circuit opening relay and that did not fix the problem. I investigated the problem myself and found that when the engine doesn't start I was getting zero volts to the fuel pump; when the engine did start I got 12 volts to the fuel pump. I verified continuity on the new circuit opening relay - OK. I checked the voltage on the connector that plugs into the circuit opening relay and found that when I turn the ignition to ON I would sometimes have 12 volts and sometimes have 2 volts on several of the pins. The appearance of 2 volts at the connector was random and sometimes if the ignition was left in the ON position would change to 12 volts after about 10 seconds. I just replaced the ignition switch last night, but won't feel confident that fixed it for about another two weeks of driving. Any comments or suggestions would be appreciated.

Thanks, this is my first post. I am new to the forum and have already learned a lot.

[texas12]

The fuel pump does not turn ON with the ignition in ON position. When you crank your engine and your Mass Air Flow sensor detects air flow, that is when the fuel pump turns ON. There is a connector under the hood on drivers side fender (single wire connector) to short to ground that will manually turn ON fuel pump with ignition ON and bypass MAF.

[wbrown05]

I checked the mass air flow sensor in accordance with my Haynes repair manual - it's OK. I also checked the Start Injector Time Switch, Vacuum Switching Valve, and Cold Start Injector. All checked out OK according to the Haynes manual. I traced the fuel lines and found no leaks. I replaced the fuel filter and air filter. Problem NOT fixed. I did notice that when the engine turns over, but doesn't start the check engine light is not illuminated. It should be illuminated when the ignition is turned to 'ON'. When it is illuminated the engine starts; when it is not illuminated it does not. Please help, I am lost.

[wbrown05]

I think I solved the problem. There is a wire that runs from the 80A fuse in the relay box on the fender to the positive terminal of the battery. The wire is about 4 gauge. A previous owner had cut the wire (don't know why) and spliced a 16 gauge wire to it with a new battery connector. I think because of the small gauge wire and corrosion the 80A fuse was being starved. I fixed it about 3 weeks ago and the truck has been starting great ever since. Lesson: Check the easy simple things first.