Truck starting problems

Could be a cold start solenoid is intermittent or sensor to it is flaky.

You could try cycling the ignition switch on and off several times before you crank it. If it helps check the fuel system. The spider fuel system is noted for problems. Key on engine off, 60--66 psi fuel pressure.

The first thing you want to check for is the brake signal,without this signal it will not crank,this is the easy one make sure you get brake light,the second is to have the starter tested by a direct method,this gives the indication of the health of the starter

replace the dynamo solenoid

by not turning over i`m guessing that you mean the engine won`t crank over,if you mean won`t start when the engine turns over then that is a different path of diagnosis.if you mean that it starts to turn crank over but stops almost immediately then this could be a weak battery,or bad starter with a bad spot in the starter,that`s why it will start sometimes and sometimes not as the starter hits and misses stopping on the bad spot.if you mean it cranks over fine but will not start then this could be a fuel pump going bad,a dirty throttle body,a bad crank of cam sensor,these usually set a code in the computer and sometimes turns on the check engine light sometimes not.you should have the computer checked for codes to see if there is any,or just a wiring problem for the ignition system

Just answered identical problem in another make of vehicle. There are 2 possibilities for your problem. A bad Keyswitch and/or a bad Starter Solenoid. I assume your Bronco did not start, which is a good thing. You could have damaged the teeth on the flywheel if the engine started.

You may need to replace the Keyswitch. It is suppose to send a signal to the "tickler" wires on the Solenoid, connecting the Battery to the Starter. Either the Keyswitch shorted and continued to power the Solenoid, or the Solenoid shorted and Welded a connection after the Keyswitch was turned OFF.

Remove the small wires to the Solenoid. If the Solenoid is welded internally, the Battery will spark when you try to connect the Battery cables and the Starter will spin. This would mean the Keyswitch may still be good, do not reattach the small wires yet.

You would need a testlight or Voltmeter to test each small "tickler" wire by attaching the testlight to a Ground and the other end to the tickler wire. When you turn the Key to Start, the light should Glow. It should not Glow all the time.

My advice is to replace both the Keyswitch and the Solenoid because of the wear they encountered with the malfunction. Then when you get the Bronco to start, go to Autozone or Oreillys for a Starter draw test to see if the Starter was damaged by your other problems. Both of those Parts stores test and scan for free.

If you have a test light, you should check the small "tickler" wires on the starter relay. You do not know if the start signal is getting from the keyswitch to the solenoid. With the small wire detached you should be able to use a test light or 12volt meter on this wire. When you turn the keyswitch to start, the tickler wire should have power. If it does not, the ignition switch is probably bad.

If the tickler does have power, then clean the mounting surface of the solenoid and reconnect the wire and see if it works. If the car cranks you were losing the ground. If the car still does not crank put the test light on the cable going to the starter and ground the test light or gauge.

You will know there is power to the starter if the test light or gauge shows power from this connection. This means the solenoid is good and either the starter itself is shorted or has lost its grounding. Check all connections by the starter and try again.
If no luck the starter is bad.

chk and clean the crank position sensor. Make sure it is firmly mounted and the connector is clean and secure.

I would clean the battery connecters or possibly change them. How old is the battery? sometimes when battery get old, they have enough juice to crank the motor but not enough to start it..But then again, if it doesn't crank at all sometimes, it could certainly be a bad or loose battery terminals..Start with this since its the simplest and easiest and could very well be your problem. hope this helps

Sounds like a crank sensor.