Only here a click when starting engine.

[HO455]

I'm of the opinion that you're suffering from the starter hot soaking. This condition is when the connections and or the insulation of the windings inside the solenoid start to fail. When cold the internal resistance of the solenoid is normal and the voltage at the solenoid is enough to fully pull the bendix out and engage the flywheel ring. When the solenoid is hot it's internal resistance is much greater and the volt drops because the factory 12 awg is too small carry the load required.

That wiring is quite long and goes through multiple connections. Starting at the main splice near the horn through the firewall plug, to the connection behind the fuse block, to the ignition switch contacts, to the neutral safety switch contacts, back through the firewall plug, and down past the exhaust and to the solenoid. That's over 8 feet of wiring, 9 connections and two sets of switch contacts. All of which when hot will have increased resistance which adds to the voltage drop at the solenoid.

When hot the voltage is applied to the solenoid after you've turned the key is only enough to move the bendix against the ring gear and not enough to force the starter gear out and engage the ring gear. Thus the click you hear. The starter gear must move enough to engage the ring gear before power is applied to the starter motor.

Having good connections everywhere and a good solenoid like the truck did when it left the factory will solve the hot soak problem.

Another common cure for less than perfect systems is to install a Ford starter solenoid in the starting circuit. When installed the start wire only has to operate the solenoid coil which only requires an amp or two. When the relay circuit is installed a 10 or 8 awg wire is run from the battery to one of the large bolts on the Ford solenoid. The other bolt is wired to the start post on the starter solenoid.

This is a common modification that has been popular for 30 plus years and there is lots of information on how it works it on the interweb. My Burban is currently suffering from this condition and I plan on adding a Ford solenoid set to cure the problem.