hi to every one i have 1999 ford f 150 lariat 5.4 L with current miles of 124,000 it does start, and sometime it does'nt ,ford mechanic had check the batteries,starters, alternator are ok, but sometime it doesnt start it has sound like scratch, and appearing to my stereo a word BAD DISk while theres no disk attached,i used a jump start and start pretty easy, theres a sound coming from the fuse box by driver the side and if that sound came out it wont going to start. pls,help me thank you looking forward for answers

 

when you say "does not start", you mean "motor does not crank over" i assume since the starter and battery have been checked. I think i would look for a bad ground wire. The problem is you say you can jump start it, and that means the battery is low. I think you need a better explaination of what is exactly happening.. Sounds like the battery is poor. You might put on a charger and see what rate it is taking a charge. You could also measure the voltage at the battery while trying to crank. The noise you hear is probalby a solenoid pulling in when you turn the key. If the battery is weak, the solenoid pulls in, and then not enough power to crank the motor.

 

If you have an owners manual look on page 152.
It shows 5 relays.
Page 153 tells you what circuits/functions those relays control.
Try to find out which one makes the noise by putting a finger on them to feel the vibration, then come back with the findings.
This will hopefully be a starting point to chase after the problem if it isn't the relay.
You can swap relays 1 and 2..
Relays 3,4, and 5 can be swapped to see if the trouble changes or clears.
Good luck.

 

to Bluegrass and Steve (1ll) thank you so much for your reply, ill put on the test tomorrow in the morning,if happens that wont gonna start again.looking forward some answers from you guys thanks again guys!!!!