Hi, i go to a technical highschool where 2 of my teachers in automotive technology class are master technicians, i bought a 1996 f150 eddie bauer edition with a 4.9L engine 5 speed manual transmission. For a few months now its been having a starting problem, where as it will crank and crank but wont turn over. First thing i did was a full tune up, and a fuel regulator since the fuel pressure was about 30 and the manual said it should be 50-60psi. I then plugged the OBD II computer to the truck and it came up with a code about the crank sensor, i pulled that off and the sensor mount was snapped in half, used JB weld and bought a new sensor since the old one unforunately broke. I thought that was the problem, next day it does the same ****, i put a new fuel pump relay in since it was only 10 bucks...seemed to work good for a week, then on my way home from work the truck stalled and wouldnt restart....Now i realize that when it doesnt start i can leave the key turned, hear a buzz almost as if the fuel pump kicks on, then she starts right up. The next time it had the problem i switched tanks from front to rear, and it still didnt start. I recall hearing ford uses 3 pumps,one as a high pressure pump located on the driver side frame rail....when i look however i only the fuel filter....no 3rd pump....am i looking in the wrong place? Does it not exist? Or is that not the problem? Some direction would really help on this one, im not going to send it to a shop since its totally random when it happens, so they will charge up the wazoo for labor. and i will also add its only stalled twice...which isd why i wasnt thinking fuel pump at first...but some help would be nice. Thanks

 

Master Technician does not mean much and that is why I never bothered with getting to be one.
Did it help? The old regulator was more than likely good. You need to run the fuel pumps with that OBD II device with the gauge on it to get the 50-60 psi.
The crank sensor is fo information only and has nothing to do with how it runs or starts.
If the fuel pumps run the relay is OK and 10 bucks is 10 bucks.
Does this buzz (fuel pumps running) last for more than one second if so you may have a bad computer.
No you only have the two fuel pumps that inside the FDM and the FDM are inside the fuel tanks.
My guess is you either have a bad PIP sensor or a bad computer.

 

Well, the pressure seemed to go up when the regulator was changed a little. And i also know for a fact a bad crank sensor can cause starting and stalling problems, ive seen it happen.
Anyway, whats a PIP sensor? and the buzz is very quick, there is 2 buzzes when i first turn the key, one doesnt happen right away when it doesnt start. I also talked to a friend who is a ford mechanic, and he said one fuel pump can cause another to not work....is this true?


One more thing, how do you know mine doesnt have that 3rd pump?

 

Not with a 1996 F150 with a DI CCD OBD II Ignition system you haven't. If you have I think Ford would like to see that one.
It is the sensor inside the distributor that tells the ICM and the PCM Computer when to have the Ignition Coil fire a spark.
I have no idea what your buzzes are.
It can not stop it from pumping but if the check valve or the shuttle valve are bad in the other FDM then you will fill the other tank from the one you are running on and you could also have reduced pressure.
Because the 1989 was the last F150 to have that fuel system with the frame mounted high pressure pump, selector valve on the frame and a low pressure pump in each tank.

 

So sub, then where do you think i should start in diagnosing the problem?

 

You need to run the fuel pump(s) with the engine not running and see if you are getting the required fuel pressure with a gauge to start the engine when it will not start.
As I recall a 300 takes about 43-45 PSI to start, any thing lower it will not start.


If you get the 55-60 PSI with the pump(s) running and the engine not running then check for spark. If you do not have any spark unplug the SPOUT shorting bar and see if it will have spark now while it is cranked. If still no spark replace the distributor or the PIP sensor.


You get spark with the SPOUT unplugged and a noid light says the injectors are not firing change the computer.

 

Well the thing is it only happens sometimes, its not a consistant thing where i can say after running 20 min it happens. Ill go to the store or something come out and it wont start, next day i could make the same trip and itll be fine.