When ignition switch is turned on, the voltage in the cb drops to 5.5 vdc

Make sure your connections are clean and tight. 13.5 may be the surface voltage, but if cells are bad, it could drop. Need to do a current draw test on it.

On older vehicles the 12 volt DC supplied to the coil comes from the ignition switch. (This is the reason not to turn the ignition switch on with the engine not running for long periods, the constant 12 VDC will burn out a coil). Check for a loose or broken wire. The ignition switch ( on the steering column) should be checked to insure the 12 VDC is getting to the coil.

The cam sensor outputs voltage pulses when the engine is running. The sensor is powered by the engine's computer, which typically provides 5VDC to power the sensor. With the engine not running, turn on the ignition switch. A cam sensor has three connections: Power (5VDC), signal output (% or 0 VDC varies with cam position), and ground return. Measure the signal voltage from the cam sensor wiuth repsect to ground. If it is 5V, slightly turn the engine's crank with a wrench until the cam sensor signal drops to zero volts. You should be able to see the signal voiltage switch between 5V and 0V while turning the crank slowly. If so, the sensor is working properly. If the signal doesn't change, the sensor is likely defective and should be replaced. They do fail.

What is wrong????????? That would be a guess on anyones part here ! Testing the electrical circuits involved would be the proper way to diagnose this no start problem ! Using a volt meter an wiring diagram to check voltage at different point's in the starter circuit . voltage drop testing ! Plus knowing how the starter system works !
Starter Circuit Operation
Voltage is applied at all times to the ignition switch from the IGN A fuse through CKT 42 (RED). When the ignition switch is turned to the START position, voltage is applied to the CRANK fuse through CKT 5 (YEL). From the CRANK fuse , voltage is either applied to the clutch pedal position switch (M/T) or the park/neutral position switch (A/T) through CKT 806 (PPL). When either the clutch is disengaged (M/T) or the transmission is in park or neutral (A/T), voltage is applied to the coil of the starter relay through CKT 1035 (PPL/WHT). Since the starter relay is permanently grounded at ground G102 through CKT 150 (BLK), the starter relay energizes.
Voltage is applied at all times to the starter relay contacts from IGN A fuse through CKT 42 (RED). When the starter relay energizes, the starter relay contacts close, and voltage is applied to the starter motor solenoid. Since the starter motor solenoid is permanently case grounded, the starter motor solenoid will energize two coils. The pull-in winding coil energizes in order to pull the starter motor solenoid contacts closed. When the contacts close, a plunger on the contacts causes the pull-in winding coil circuit to open. The hold-in winding coil then holds the starter motor solenoid contacts closed. Voltage is then applied to the starter motor from the battery through CKT 1 (RED) and the closed contacts of the starter motor solenoid. Since the starter motor is also permanently case grounded, the starter motor will run until the ignition switch is moved out of the START position. When this happens, a spring in the starter motor solenoid moves the starter motor solenoid contacts and the plunger back to the rest position.


Starter Voltage Drop

How to voltage drop test starter motor circuit

charge the battery , clean the posts and connections,,

it sounds that you have a voltage drop caused by bad wiring or a bad connection for the wiring of the trailer plug. you need to check the wiring of the trailer plug wiring back to were it connects to the truck wiring.pay attention to the condition of the plug connector itself.

Can you explain more so I can help. What do you mean still wont turn on, engines doesn't start or starter motor doesn't turn. Have u taken out a spark plug and connected it to the cable put the end of the spark plug to a ground and make someone turn on the engine for a few seconds you should see some blue sparks. Carefully use gloves. If no sparks, spark plug is bad next thing to check instead of putting the spark plug in the cable put Philips screwdirver put the screwdriver near a ground not touching about one inch make someone turn the engine for a couple of second you should see the spark jumping from the screwdriver to the ground, If there are no sparks ignition coil or spark plug cables are not good. But u say u changed ignition coil so maybe your cables are not good. There is a connector near the ignition coil disconnect it and turn ignition switch on measure the voltage you should have in between 12vdc + or - .5 vdc if no voltage present there is a blown fuse, Check for it

you should also check the crank position sensor this is what tells the ecm when to spark. this is a prox switch and when unplugged and checking ohms while cranking you should see a sqaure wave. should go from 0 ohms to infinity. when these go out you will not get any spark on any cylinder

Strap VOM across battery and measure VDC. Keep Eye on VDC as someone attempts to start car. If Volts drop to near 0, battery is toastado.

Otherwise, check ignition relay and starter solenoid. Check any large fuses in the underhood fuse compartment.

first check the condition of all circuit wiring for damage. Inspect all connection to the starter motor, solenoid, ignition switch, and battery, including all ground connections. Clean and tighten all connections as required
next
Check the voltage drop between the negative battery terminal and the vehicle frame by placing one lead of a voltmeter on the grounded battery post (not the cable clamp) and the other lead on the frame. Turn the ignition key to the START position and note the voltage drop.
Check the voltage drop between the positive battery terminal (not the cable clamp) and the starter terminal stud. Turn the ignition key to the START position and note the voltage drop.
Check the voltage drop between the starter housing and the frame. Turn the ignition key to the START position and note the voltage drop.
If the voltage drop in any of the above is more than 1 volt, there is excessive resistance in the circuit. Clean and retest all cables not within specification. Replace as necessary.
let me know what happens