86 fordtruck new starter tuck want turn over...

85 & 86 are the control side of the relay , one should have battery voltage (85) the other (86) doesn't .86 is control from the PCM - engine computer . PCM supplys a ground to close contacts inside the relay sending battery voltage to the S terminal on the starter solenoid . If the PCM doesn't see a voltage signal fron the park neutral safety switch it won't energize the relay .
Circuit Description (ECM/PCM Controlled)
Moving the ignition switch to the START position sends a 12-volt signal to the engine control module (ECM)/powertrain control module (PCM) Crank Request circuit. The ECM/PCM verifies that the transmission is in the PARK or NEUTRAL position. With the transmission in Park, voltage flows through the Park/Neutral position switch and feeds the starter relay coil. The PCM then grounds the control circuit of the starter relay. When the starter relay is energized it allows battery positive voltage to the starter solenoid S terminal. On some vehicles the starter will continue to crank the engine with the key released until it starts or the crank command has timed out to prevent excessive heat build up in the starter circuitry or the ECM/PCM receives an engine run flag.

assuming battery fully charged hook test lite between good groud and small starter terminal have somebody to crank if lits chek power and ground to starter and replace starter if no lit go to starter relay terminal 30 and 87 use a piece off wire and momentarily bridge them if starter bumps the engine check terminals 85 86 one is power when cranking the other is ground if starter bumps and test lit hooked to 85 86 lits replace relay if no lite keep tracing ckt to ignition switch

Yes there are a couple of reasons your car may not turn over. Low battery. Faulty starter motor,( tap the starter on the side with a hammer this will free up a stuck pinion gear) or internal engine damage. Were there any problems prior to it not turning over?

Is it just clicking, like the battery is dead? Will it turn over fast, with the spark plugs removed?
I would try using jumper cables, and try giving the starter a better ground -. Clamp to starter housing and negative side of battery. (NOT + TERMINAL) .
If these make no difference, I would buy a NEW starter.

Battery, and Battery cables off the starter ,starter relay and ignition switch. These are the remaining items in the starting system for no crank and no start.
Get Shop manual and do the appropriate testing for each.

The solenoid on your starter is probably no good. Just get a new starter. Theres no starter that will "grab the teeth better", theres just new ones that work and old ones that **** out

Sounds like the starter went ban and there's an internal short in it.

Sounds like the starter could be bad. Chect all ur grounds and the hot cable to the starter. Also check the trigger wire on ur starter.

use a 12v test light and check for voltage on small solenoid wire at the starter while turning the key to start.This will let you know which way to go .There is no relay involved that would interupt this signal to the starter from the ignition switch unless added aftermarket for an alarm system.

This Problem is your Starter and Starter Solinoid. Get a New Starter (Solinoid Should already be on the New Starter).