What might be wrong with our truck?

General Questions
#1

We have a 2001 F-150 pickup. In general, it runs wonderfully, but the past month or so sometimes when I turn the key, the engine doesn’t turn over. Lights/radio, etc, come on, but it acts like I’ve just turned the key to the “on” position, rather than all the way to start the truck.

It has a new battery.

When it does turn over (which is 95% of the time, so far) it starts right up and runs great.

If it doesn’t start, I can make it start by turning it all the way back off and trying again. Today this took about 4 tries before it turned over.

What is likely to be the culprit, here?

Thanks.

#2

Lose or corroded battery terminal or connection on starter relay.

#3

Checked the battery terminals, they’re tight and look good.

I’ll look into the starter relay thing. Thanks.

#4

Probably a failing ignition switch. Could also be the starter solenoid.

#5

Or the starter itself.

#6

Watch carefully next time you start the truck succesfully. Some of the warning lights should either go out or come on when the key is turned from “on” to “start” but before the truck actually starts. If the lights don’t go out/come on when it’s not wanting to start, it is almost certainly the ignition switch or the cylinder. If they do behave normally, then it could be the starter or the solenoid or the relay, etc.

One other “worth a try because it’s cheap” suggestion is just use a different key and see if the problem goes away. Sometimes as both the key and the lock cylinder wear out, you have to work it back and forth to get the tumblers to line up right. Also, as this was one of the earlier chip-key vehicles, it could just be that the battery on the chip is almost dead.

ETA: it could still be the ignition switch/cylinder if the lights seem to be behaving normally, BTW.

#7

I have a 2000 GMC with an after market immobilizer (mandated by insurance company to combat rash of thefts). The ignition won’t engage unless a little fob on my key chain is in just the right position near the steering column. In time, the battery in the key fob will weaken.

#8

Among the possibilities:
Starter (~90% chance)
Ignition switch (not the lock cylinder, but the electrical switch)
Alarm/antitheft system fault
Starter relay
Neutral safety switch or clutch safety switch

To test for this symptom, the first thing I do is hook a test light to the starter’s “trigger” terminal. Then I have to catch it in the act, which can be vexing with an intermittent problem*. If the test light goes on but the starter doesn’t crank, I know it’s a bad starter. If the light doesn’t go on when it fails to crank, I need to move the test light to the next most likely and/or accessible suspect.

*If I can’t catch it in the act, the thing to do is try again after a few days or weeks after it gets worse and it’s more likely to act up for me. This type of symptom will get worse, usually both in frequency of occurrence and in how many tries it takes to get it to turn over. Eventually it won’t crank, period.