urban_trapper

I have a 99 f150 4x4 with a 4.6L...It is turning over and not starting...when we put quick start in it it fires right away and will run fine...only sometimes it won't start first thing...we replaced the fuel pump and assembly and it ran great for about 3 days then the symptoms came back...we checked the relay and its fine...we can't hear the new pump prime but we could hear the old one prime even when it wouldn't start...it doesn't seem like it has any loss of power up top or down low...we used a fuel pressure gauge and it showed just fine when running and a little pressure when the key is turned on but didn't show anything when turning it over when it wouldn't fire.

please help cuz we are completely out of ideas...thanks in advance

Jbrew

Have you replaced the filter ?

How is the regulator ? Yea, that needs to be checked.

What was the FP psi ?

Yea, first thing is to confirm is a fuel delivery issue, - which it sounds like you have now. Make sure the inertia isn't tripped currently.

Have you scanned the KAM ?

Carcrazygts2

There is no visual inspection of a relay. It probably old. Replace it. Also replace the filter. Try another key also to see if it changes how the truck starts.

urban_trapper

Thanks for the quick replies...I am going to replace the filter tomorrow...we heard the relays clicking so we figured they were good and we swapped the pcm relay and pump relay and it didn't make a difference...since the truck starts with quick start and runs fine after its started we figured it wasn't the inertia switch...we tried the other key and it made no difference...we bench tested the cam position sensor and it was good...it did throw a code just before we replaced the fuel pump and it said P0172 and P0174 which is the left fuel bank is too lean and the right fuel bank is too lean...we wiped the codes when we replaced the pump and they haven't come back...we didn't check the regulator...we didn't even think about it...thx for the idea Jbrew.