hick-hanna

Hey, so my F150 keeps dying while I'm driving. I just bought it, and after driving for about 45 minutes I stopped and it died, but started right up. Then I was going around a bend at about 20 mph and it died, I pulled over and it started right up. I was at a stop light and the voltmeter on the dash was going down? I tapped the gas pedal and it went up.....it drives very smooth and starts up nicely..so I was thinking it was the alternator but I'm not 100% sure. Thoughts??

fltdriver

Sounds like Throttle Position Sensor or IAC, pull the IAC and clean with Throttle Body cleaner, also hit the blades (back and sides or them) of the throttle body as well as where they contact the throttle body. This should solve that issue, if not then get a multimeter and test the TPS voltage, should be .9-.97v closed throttle and 5v WOT, if close you can loosen the bolts and adjust it until you get proper reading. If not even close or it doesn't increase smoothly when moving throttle to WOT then replace it but be sure to find and read and re-read and follow instructions on replacing. It's simple but there is a specific way to do it. If the first doesn't help and TPS is good then you need to check for vacuum leaks, use vacuum gauge as it's the only way to truly test. Ask more questions if you need to but including you engine size as well as other basic info (manual, 2wd or 4x4) may help.

broncojunkie

I wouldn't trust the gauge too much, but I know the factory alternator on these trucks aren't much. I guess if the idle drops down too low, the alternator might have trouble keeping up...especially if you have a bunch of electrical stuff running. If it's dying and starting back up, I guess it could have something to do with the charging system, but it's all related...so don't go replacing the alternator if you're not getting enough power. If anything, check all your battery terminals, cables, grounds etc. first. Fix anything you find that needs attention. Then, take that alternator off and have it tested. It comes off pretty easily. You can have it off, tested, and back in the truck in a couple hours...and that's taking your time. If it turns out that the alternator isn't putting out enough, you can replace it or you might save a few bucks and just get a brush kit. I think some of the parts stores stock them. Just beware, though, that an old alternator may have bearings that are on their last leg, anyway...not to mention the voltage regulator, which is attached to the alternator. You can replace that, as well...but I've found that it's almost as cheap and better insurance just to replace the whole alternator.

There are tons of things, unfortunately, that can cause it to die while driving, unfortunately. Could be the tps...fuel filter, tank or lines, the tank selector switch (if you have dual tanks), a bad wire just about anywhere in the ignition system, in need of a tune-up, fuel filter, etc. The charging system is a good place to start, though. Next, I would probably check fuel pressure, since it's easy to check. Go from there and see what you come up with. Good luck!

hick-hanna

Well since my fuel line has a hole in it I'm going to guess that's what it is lol. It is leaking gas like there is no tomorrow. Any one have any idea on what it might cost for a pressure and return line? 1990 F150 SLT extended cab 4x4 5.0 v8

fltdriver

Go to rockauto.com an look it up, then google the part # to see if there is a better deal somewhere else. Remember that amazon has free shipping on most stuff when it's >$35.

Chris_1

iTrader: (1)

If you don't have enough fuel pressure at the fuel rail (bare min. 30 psi, 40 to 45 is better) then the truck won't run.
Which is probably just as well, because if you're leaking gas it's just a matter of time until it goes boom.
Probably shouldn't take anybody you like for a ride till that's fixed.

hick-hanna

Good to know....thanks guys!