Just won't start sometimes

[Cocjr2005]

Hello all, I am having a problem with my 2004 Ford Explorer Sport Trac in that sometimes it won't start. It initially starts every time but if you were to stop it won't start again consistently the only thing that is common each time is the passage of time, about 15 to 20 minutes. I have changed the electronic portion of the ignition switch I have cleaned all my Terminals and grounds don't know what else will can be. Some folks say it has something to do with the theft deterrent system and when that happens to them the theft light flashes erratically mine is in doing that so I'm not sure if that's the problem. If anybody has any suggestions or if had this problem please tell me what you did to solve it.

 

[koda2000]

I'm thinking worn fuel pump. My '01 Eddie Bauer 5.0L did this on/off for a couple of years before it finally would not start at all. I replaced the fuel pump and it now starts instantly every time.

 

[Cocjr2005]

I'm thinking worn fuel pump. My '01 Eddie Bauer 5.0L did this on/off for a couple of years before it finally would not start at all. I replaced the fuel pump and it now starts instantly every time.

Thank you for your suggestion but I'm thinking it isn't the fuel pump because it doesn't even turn over. I'm thinking it's something in the starting circuit. The starting circuit isn't send power to the starter solenoid to engage the motor, for some reason. Did it not even turn over when you had your problem?

 

[koda2000]

Unless you have an aftermarket anti-theft system, the OE anti-theft system has nothing to do with the starter motor. Sounds like you have a bad electrical connection somewhere. I would start by checking the "S" wire at the starter motor when this is happening to see if power is even getting to the solenoid when the key is turned to START. Your problem could be a lot of things. I suggest you work backwards from the starter. Does the solenoid click loudly when you turn the key to START? You're going to have to trace down your issue yourself, there are too many possible failure points to list. This is why paying someone to find the problem is so costly. Diagnostic time is expensive.

 

[Cocjr2005]

Thank you very much, you are exactly right. I have thought of seeing if there is excitation voltage at the starter when the fault happens but I never have another to turn ignition key. I'm thinking on purchasing a remote starter switch to carry to see if that works. But to answer your earlier question, no, there is no click or indication of power transmission. Thank you again and I will take your advice. Starting at the starter is the way to go. I also will purchase a manual having electrical schematics to have an better idea of what to expect. I fully intend to post my findings once this dragon has been slain.
Clyde

 

[koda2000]

Thank you very much, you are exactly right. I have thought of seeing if there is excitation voltage at the starter when the fault happens but I never have another to turn ignition key. I'm thinking on purchasing a remote starter switch to carry to see if that works. But to answer your earlier question, no, there is no click or indication of power transmission. Thank you again and I will take your advice. Starting at the starter is the way to go. I also will purchase a manual having electrical schematics to have an better idea of what to expect. I fully intend to post my findings once this dragon has been slain.
Clyde

If you don't have someone handy to help you, you could buy an inexpensive test light, cut the tips off test leads, keep the test light in the cab with you and extend the wires wiring one end to the "S" terminal on the starter solenoid and ground the other end (anywhere it's convenient). Test the light when the truck is starting okay to make sure the light illuminates. The next time the starter wont crank see if the test light is coming on. If so, replace the starter because the solenoid is faulty. If the light doesn't come on, you're loosing power somewhere.

Oh, one thing I learned a long time ago is to test a test lights right on the vehicles battery before using them. I once bought a defective light and wasted a lot of time wondering why I didn't find power on whatever I was testing.

Possible points of failure to test:
power to ignition switch
power out of the ignition switch
power in/out of starter relay
ground on starter relay
corroded/lose terminals for starter relay in power distribution box
bad wire somewhere

Have you tried putting the gear selector in neutral when it wont start in PARK?

I chased an very intermittent starter issue on a classic vehicle for the better part of 20 years. Replaced starters, solenoids, neutral safety switch, ignition switch. It drove me crazy. I finally had had enough and vowed to fix it. It turned out the wire going to the "S" terminal of the starter solenoid had a partial break in it somewhere, causing too much resistance. While it always carried power when attempting to start, under a load the voltage to the "S" terminal would drop from 12 to 5-6 volts when put under a load. I ended up replacing the wire (which I hated to do, as it was a very correct restoration) but that finally got me around the problem.

Besides a test light, if you don't own a VOM (volt ohm meter) it's a good tool to have when working on anything electrical and provides much more information than a simple test light. I'd love to buy something called a Power Probe, but I can't justify the expense.

Tip: If the starter relay's connection is suspect and the terminals in the power distribution box are not corroded, take a pair of pliers and slightly twist each of the blades on the relay. Doing this will effectively tighten each of the receptacles. (Great tip provided by another forum member).

Good luck and let us know way you find.

 

[Cocjr2005]

That's a great idea about the test light. I'll rig that up to get closer to the problem. I have moved the gear shift to test the neutral safety switch but no luck there. I do have multimeter and know how to use it. I carry it with me now but by the time someone comes around it starts. Interestly enough it always seems to start initialy. After sitting for a period of time seems to reset something. That suggests to me a thermal dynamic going on. Maybe a ground somewhere.