Hi, I have a 99 F150 and I'm having some weird issues with starting it. I'll start from the beginning, I started the truck and backed a trailer up to my garage, turned the truck off, unhooked, and went to start the truck. When I turned the key I got a sound that sounded like a solenoid, (a few loud clicks and it wouldn't turn over) and then the theft light started blinking quickly. I tried the other key, and tried them both a few times and that didn't work. When trying it that night sometimes the interior lights would turn on and off a few times or not come on at all, and every once in a while a relay in the fusebox would start clicking when I turned the key off and wouldn't stop until I turned the key back on and off again. I charged the battery overnight and tried again this morning. Now all the lights work properly, and when I turn the key on, the gauges sweep, and all the dash lights turn on like normal, when I try to start it either does nothing, or a few loud clicks, but if I just leave the key on ACC, I hear a clicking under the hood, it seems to be coming from the box underneath my air intake (it has brake lines going to it) and on the dash the ABS light turns off every time this box clicks. So.... could it be the ABS module that won't let the truck start? Is the ABS module and ECU the same box? Or could it even be a bad connection somewhere causing this? Or a bad battery? I haven't dug too deep yet, and its going to the mechanic on Monday, so if anyone has any ideas I'll see if I can try a few things before I bring it in.

Thanks

 

My non professional advice would bet to get a ODBII scanner and check if it's throwing a code. That and check all fuses and relays.

 

Checked the fuses, they're all good, haven't checked relays yet.

 

If you have a voltmeter and a helper, you may be able to make quick work of this.

Charge up battery again. Then measure battery voltage with both meter probes pressed down hard into THE TOP OF THE BATTERY POSTS THEMSELVES, not on the battery cable clamps.

While monitoring voltage directly at the battery posts, turn key to RUN. Battery voltage should decline slightly.

Then turn key further to START. If battery voltage drops way way down, bad battery. If battery voltage does not drop much further than what it was in RUN before, in other words battery voltage is holding up high, then I would suspect a battery cable to battery connection corrosion problem, take off clamps from battery and clean. Or it may be a battery or ground cable high-resistance connection problem requiring a bit more digging. But start with the easiest and most likely FIRST - - - the battery or the connections to it.

When the factory battery went under the original factory warranty on my '97, after a few solenoid clicks, and trying further to start it, all hell broke loose after battery voltage was low enough not to properly power the factory alarm system. There were relays clicking and clacking all over the dash and underhood.

EDIT - I should have mentioned that if you have an old low-tech analog meter with a needle that swings, that is good for this type of test, as if relays start clacking and the measured voltage is chattering, at least you can see the general voltage area. Some digital meters will not be able to keep up with a load on/load off fast chatter, and will not display anything useful because they can not sample/hold/approximate fast enough internally.

 

this sounds like more of a PATS issue.

a brief discription PATS Key System Programming .: Articles

try the other key...see if it works.

the other thing to check or maybe ask you ...DO you have a aftermarket alarm or security system on it...or perhaps a aftermarket remote starter?

If yes...then disengage ( pull the fuse) the system and see if your starting issues go away. Sometimes these aftermarket things will short out and cause starting issues.

 

New battery did it, i'm just amazed how fast it went bad, it was litteraly five minutes between startups, the first time it worked normal, the next time, nothing, and everything went bazerk. I had the battery tested and it was shot, put a new one in and everything works great. Thanks everyone for the advice, it saved me a potentially expensive and embarrasing trip.