2008 F150 XLT 4.6 automatic.

I've been trying to solve a no crank issue for a couple of weeks now.

About a month ago it would occasionally not crank. Sometimes it would take a couple of tries.

Here are the things I have tested/done

PATS system flashes like it should
Starter relay in passenger kick panel clicks
Cleaned all grounds under the hood and on frame (just under the washer bottle) all show continuity on my meter.
Cleaned grounds behind passenger fuse panel.
Cleaned grounds under passenger door.
Had battery and started tested (both good)
Battery terminals clean and tight
Good continuity in ground cable from battery to starter and hot cable to starter.
Checked and cleaned all starter/pcm related fuses and relays in passenger side fuse panel.
Checked the OTIS diode on drivers front fender.
Tried the spare key.
Tried shifting to N
I do hear the fuel pump prime when key is turned to ON.

Also no check engine light or faults on the odometer and no codes that I know of.

I don't think I am getting voltage to the "S" terminal on the starter solenoid. I don't hear a click at the starter solenoid and when I checked it with a volt meter didn't get any voltage when the key was turned to "Start"

I tried jumping the transmission range sensor plug to no avail.

New issue started today: Sometimes when it starts, it dies almost immediately. Then will fire up on the next try or two.

I've searched the inter web and tried all possible solutions I have come across.
Really scratching my head on this one.

I don't know if it is related, but since about January the interior and cargo lights will come on randomly. I traced that back to a loose wiring connector the runs on the left hand side of the gauge pod. Wiggle it and it goes on and off. I cleaned it and reconnected it and it has been better, but still happens usually after a bump in the road, but not always.

What's left? Open up the wiring harness and trace the "S" cable back?
Where does that cable come from? It is in the same harness as the ground and hot to the starter. Is there a fender mounted solenoid I have missed somewhere under the hood? I know some later models had one, but I haven't found one on mine.

Ignition switch? I think if that were bad, I wouldn't get the relay to click/activate.

 

As soon as I saw the title. Of the thread. I thought ignition switch. I've. Not heard of one go bad on these trucks.
​​​​On just about everything else that's had a no crank on other vehicles I have owned or come across with mates. It's been the ignition switch worn.
Are you able to hotwire it to check starting. As if it starts Everytime like that definitely switch I would say. Seeing as you seemed to have thoroughly checked everything else.


Hope that helps
Roland

 

I will also add that it has a dealer installed KARR Security system.

It seems to be arming disarming normally. At least the blue light flashes like normal when armed.

 

Check and see if that system added a starter interrupt relay. If so, bypass that relay and see if the problem is solved (or not).

While you're at it, pull the kick panels in the cabin and inspect all of your grounds behind them looking to rust, corrosion, loose connections or body rot.

 

There should be a connector by your battery that leads to the solenoid input on starter . Clean that . Use a 12vdc light that you rig up to see if signal getting to solenoid on starter . It is possible you have a defective starter or a bad main lead to starter . They can go bad inside insulation . the nice thing about the testing light is putting it anywhere you can
see it like on the windshield . This should lead you to your problem . You can solder in any 12volt auto bulb to long wires. A little tape or liquid insulation will work . Some guys use pvc glue -that will work . If your solenoid gets the signal but it doesn't crank test main lead at starter and see if bulb dims or loses light . You can have loose starter bolts or a bad motor ground ,easy enough to throw jumper cable on to supply ground from battery .
There is a away to do a voltage drop test across a bad suspected lead. just connect a voltmeter from one end to the other and crank , no volts should show up or very little.
Use very good leads to replace not cheap stuff ,maybe go to napa.

 

As a follow up, it turned out to be the ignition switch. Now if I can just get the damn bottom half of the shroud in place I can finish.

I was almost ready to tear out the KARR alarm system.