I just bought a 2003 F-150 5.4L. It had a bit of a long start when I bought it, but after taking it to a mechanic prior to purchase, he said that the fuel pump needed to be replaced because there was a valve in the pump that holds the pressure (40-50psi) so that the vehicle starts right up. This valve was supposedly bad. I had them replace the fuel pump and filter. That night when I picked up my truck after hours it took even longer to start. They told me that they were going to warranty the fuel pump and they put a new one on the next week. I just picked it up last night and now it's even worse! It takes 15-20 seconds for my truck to start now!!! I'm scared that if I take it back to them my truck won't start when I get it back! It doesn't matter if the engine is warm or cold, if it was running, every time I start it, it is 15-20 seconds to get it started...any suggestions?!?

Edit: it came with a cold air intake installed and I put on a superchip - not sure if this is relevant to my issue, but just wanted to make sure all the info was here!

 

I would dump the superchip just out of general principle.

You really need a fuel pressure gauge attached to the fuel rail under the hood so you can see what's going on.

 

I think yer mechanics butter has slipped of his biscuit. Try this before doing anything. Turn the key on but do not start. Wait 5 seconds and turn it off. Do the same thing 3 times. On the forth try start the truck. If it takes a long time to start, it's not the fuel pump. The pump only works for the first 3 seconds to pressurize the system and then turns off. It starts again once the engine is running.
FWIW, you can buy a fuel pressure gauge at Harbor Freight for 20 bucks. It works great and it screws on the Shrader Valve....the thingy on the fuel rail that looks like a tire valve stem.

 

Just out of curiosity, why would you dump the superchip? It had this issue prior to me installing it...would you recommend a different chip? If so, why? Thanks for your help! I'll be working on my fuel issue today, right after I run to harbor freight!

 

Tire valve "thingy" I actually laughed out loud!

 

Superchips and their ilk often cause issues that either create new or mask old issues.

 

Yamaha, I had a similar issue with my previous truck.

Took it to the dealer, they couldn't reproduce it 100% but replaced the plugs, cleaned the TB and MAF and replaced my battery. When I went to pick it up it was just as bad as before. Cycling the key to run the fuel pump several times before starting was a "band-aid" at best, since the injectors still had to bleed out the air in the fuel line before getting good fuel flow.

I bought a fuel pressure gauge and drove around for a couple days with it tie-wrapped to the motor. What I found was that after a couple of hours sitting the rail pressure would drop to 35-40 PSI and to 0 overnight. Another symptom was that sometimes during cranking the motor would seem to "seize" momentarily and then keep turning over.

Because I had the guage I was able to relay all of this information to the dealership - they suspected a leaking fuel injector was the cause of the pressure loss and the hydraulic lock. They had it overnight, scoped the cylinders and sure enough found fuel pooled on the #1 intake valve. 6 new injectors later everything was good to go.

Do yourself a favour and pick up a fuel gauge - it can tell you a lot about what's going on.