Last night, while rolling up to a stop sign, my truck died. Went to crank it and only one click, Autozone checked battery and said it was bad so i replaced with a brand new battery. Put it in, still only one click. I'm pretty sure its the starter but not sure if its the relay or what. Been trying to read some forums and alot of people make it confusing. Please help me out.

 

Myself, hit the starter with a hammer, just a good little tap. Supposedly, it works temporarily, but you're gonna have to check a few things regardless. The connections on the starter, corroded? Clean and gob dielectric grease on them (in the red cover too). Check the solenoid which is on the pass. side, sorry, no pics. Battery terminals (same idea with starter connections) and alternator. Sometimes when one thing goes, more goes with it. Check also the alternator field fuse under hood. The fact it died when already running means it's more or something else besides the starter.

 

Get a voltmeter
Check the big wire on the starter it should have 12ish volts all the time
The small wire on the starter should have 12ish volts when you turn the key to start.

If both have 12ish volts then you have a bad starter.

If the big cable doesn't have 12 constant volts check your battery terminals or fusible link

If the small cable doesn't show 12 when the key is turned then you need to track it down from there. Follow the wire up and test for voltage at each connection. Eventually you will find where it has power. and the problem will be some place before that point. Im assuming this is on a 98 f150, the starter relay is on the firewall, that could very well be the problem. If you trace it all the way into the cab into the fuse box it could be an ignition switch.

Or you could have a loose connection on the starter or relay, I have seen that a few times.

 

Before I would do anything. I'd give it a few taps with a hammer..Not real hard..Break it loose..I had same problem and gave her a few taps and away we when..

 

Probably starter solenoid . Sits on top of the starter.

 

low voltage makles DCelectric motors run hot
your vehicle is a 98- so thwe starter has been around for few miles
in additon to the voltage drop tests you can have a good shop place an inductive ammeter of the positve cable to the starter and measure for excessive current draw
you can also remove the starter and have an auto parts store test it
some autozones can do current draw with the starter on the truck
if you end up removing the starter there are 2 ways to do it
the book method or the easy method

easy method
jack the right front up remove tire and place jack stand under frame
remove plastic fender liner - takes about 5 minutes
disconnect electrical connections
unbolt starter
you will need a long extension to get the bolt that is hidden by the starter next to the block- a swivel extension or a universal will help