'96 V-6 XLT Intermittent Starting Problem Solved

The power consumption of the ignition circuit is tiny compared to what the starter draws. What you are suggesting is highly unlikely.

I had the same problem on my '97 4.0L V6. I removed and cleaned the crankcase position sensor connector (bottom front of engine). I also replaced the battery. I'm pretty sure it was just the battery that was the problem: enough power to crank the engine but not enough to make a spark. I guess the computer decides that it's better to leave you stranded where you are than leave you stranded where you are going.

I suggest making sure your battery connections are clean and tight and check the cells with a hydrometer. I suspect you will find one or two low cells. Car batteries seem to have a habit of being OK and then suddenly dying (right about at the end of the warranty period). BTW that particular battery is so bad now it will not accept a charge at all.

My understanding is that a "bad" crankcase postiton sensor (or sensor connection) will cause a "no spark" condition because the computer doesn't know the position of the crankcase so it basically says "to hell with it." When I checked my sensor connection it looked like it could use some cleaning but didn't really look all that bad. I surmised that the problem was probably not the sensor connection but the battery. The battery was definately bad. Having a system that would decide that it's OK to crank the engine but not allow spark due to a slight decrease in available battery voltage does not seem like a good idea to me and I certainly don't like it but given my experience with other kinds of computers it did not seem impossible or unlikely to me, just unreasonble. From what you are saying then it probably was a dirty connection on the sensor. It was my #1 suspect partly due to it's exposure to the elements.

In any case the problem has not returned. :-)

Try this simple test - Before actually starting the truck, switch the ignition switch from off to run three or four times (not to start). Each time you switch to run, pause for a count or two to allow the fuel pump to run. After the third or fourth switch to run, try starting the truck. If it always starts up promptly, then chances are you problem is either a failed check valve or a leaky injector. If it is a leaky injector you should occasionally get a cloud of black smoke when the truck starts, otherwise it is probably the check valve in the pump assembly (i.e. fix = new fuel pump). You could get much the same indication by checking the fuel pressure after the truck sets for an extended period.

Ed

If you have a weak battery, the system voltage can drop so low when you are trying to start the vehcile that the PCM doesn't perform properly. Modern starters will run at a much lower voltage than in the old days. However, under these conditions they draw a lot of current, which knocks the system voltage way down.

Ed

Since I was in a situation where I could not reproduce the fault in any predictable manner, I read about others' experiences on other Explorer forums. The top culprit and my first "shot-in-the dark" was the fuel pump relay. At $10 it was cheap to try. My next item would have been the crankshaft position sensor. But the relay fixed the problem.

This may not be an elegant way to do trouble-shooting, but if you can't reproduce the trouble and have no fault codes set, it seems reasonable to try some low cost fixes that have been reported by others. Len

The first thing I did was go buy a fuel pump gauge and check the fuel pressure. That tested OK on mine. Next I checked for spark which took some time waiting for the engine to misbehave again. I had no spark. I checked the voltage at the coils and a bunch of other stuff and everything tested OK.

I hope your new relay solves the problem.

BTW you can get your battery load-tested for free at many auto parts stores.