Anyone have specific suggestions for how to begin diagnosis -- tools and techniques -- to identify the cause of the following problem:

> 1997 F150 4.6 will not turn over
> Battery and starter pass test w/ flying colors -- good strong battery; R&R'd starter and tested on the bench...
> Dash & head lights are bright and strong
> No warnings leading to this problem; stopped for gas; hopped in; attempted to start the truck and nothing -- just all expected dash lights; not even a click.
> Fuses under dash and in "Power Distribution" box check ok.

HELP -- where to look next.

 

There is a start relay that the ignition switch has to energize.
Look for a lead off or broken, a defective relay.
It's all there is between the battery and the starter besides the cables to each and the ground to the block.
If you can energize the relay by applying battery to the start terminal and turns the engine over ok, then the ignition switch is suspect.

 

Check fuses and relays both under hood and under the dash. You did check your starter silenoid? I believe on the 97 it is on the drivers side inner fender, (if not then it is on the passenger side) which ever side your battery is on there it will be. My wifes 97 Explorer has a cronic problem going out once or twice a year. All of a sudden she will get in it somewhere and it wont crank. When it goes bad she now knows how to jump across it and start her car to get her to the auto store and what it should look like when she buys it. LOL
If it's not the fuses, relay, or silenoid, then it has to be a bad wire or connection. Break out the voltmeter and check to make sure your getting power to the silenoid then from the silenoid to the starter if positve side is good, then check the ground to the block.

Luckily for you if you know its a good starter and battery...there is very little else to go wrong and everything else that there is, cost about $20 or less each.

 

My '97 had similar problems. The dealership said the positive wiring harness was corroded. They replaced for $275.00. No problems since. Wish I had one of those $20 problems.

 

Interesting....On my wifes 97 Explorer it isn't an actual harness the positive wire does run in to the loom but each section between componets can be bought and replaced seperatley. The F-150 maybe different, I have not looked at my 2000 yet since it hasn't had a problem "knock on wood" so it could have a harness of sorts or atleast not sale it in pieces anymore. I buy most parts at O'riellys Auto and the aftermarket sometimes has options dealers can't offer too. Plus I do almost all of my own work so dont have shop fee's included either. Local dealer shop fee is around $45 an hr with a 1 hr minimum, Then they go by book rate or how long it actually takes them which ever is greater.

 

had my 99 towed twice for the same reason. turned out to be the negative leads at the bottom of the starter. they are exposed and receive water and salt from the road. each time I was out of town when the problem occurred and subjected to $400+ repair bill.

After looking at the connection I think a pair of jumper cables, with on end connected to the broken wire and another on the fender will get the vehicle started and at hopefully home.

Also, the firewall mounted solinoid in my wifes '97 f150 failed. I managed to use the screw driver across the two power leads on the starter to get her home.

 

I'm wondering if the selinoid is a common weak link. Like I mentioned earlier in this thread my wifes goes out once and sometimes twice a year. This last time that it went out I bought a 50 amp push button switch and put eyelet connectors to wire it to each side of the post on the silenoid so she can just hit it to start it and get her home if/when it goes out again. It scares her when she has to use a screwdriver, so that should keep her from having to now.

 

My 97 with 4.2 had this problem and so did a friend of mine with the same 4.2. The positive cable connection at the starter gets corroded and makes the starter not turn over at all. I took off the connection at the starter and cleaned it with a small wire brush and reinstalled it. Works fine now. Now I have a new starter solenoid on my work bench waiting for the one on the truck to go out. I don't know if the 4.6's have this problem. Good Luck.

 

My '99 4.6l did the same thing. After replacing the battery with no fix, I traced the problem out. The positive (or negative...can't remember) wire corroded and disconnected at the starter. Took out wiring harness. Soldered on a new end. Replaced harness. Works great.
Glad it happened in my driveway!

 

Good info folks. My 2000 5.4 exhibited similar symptoms over the weekend, lots of power, single click when trying to start, no start. Solenoid is good. After reading this I ran a booster cable from the batt neg post to the ground post on the starter and got a start. Pulled all the connectors off the starter side, cleaned them up, and put them back together with dielectric grease and it seems to work fine.

Don't mind cleaning them up every few years, since the harness runs about $150, but would have rather seen Ford design them such that the terminals aren't exposed to crud & humidity. They went to the extent of putting heat shrink on all the ends, but left the tips exposed, so water gets in and mucks them up in a spot that's tough to catch on an inspection. 4 years doesn't seem like a long life for a simple thing like a battery cable.

Thanks for the tips.

 

Seeing these posts make me think about getting some dielectric grease and smearing it all over the starter posts.