I bought an 08 F-150 4.6L about 6 months ago with 95K miles. It was starting fine when I bought it but lately has been having some issues when starting. I recently had the alternator rebuilt and bought a new battery. These were needed maintenance and not just blind attempts at fixing my problem, but the problem does remain.

So here are the symptoms:
-When starting the truck in the morning it sometimes takes the engine a full cycle to turn. Sometimes it will even stop trying to start and I have to turn the key again. But it always starts immediately on the second try if it takes that long.
-It usually doesn't do this if the truck has been running recently and will start just fine. However, if it sits for a few hours it usually has a bit of trouble starting.
-I'm sure the problem is fuel related because it seems to get a little worse when my tank gets close to empty. And doesn't seem to be quite as bad when I fill up with premium (which I've been doing since the problem began) vs filling with regular.
-I've tried using Seafoam and other fuel additives and they seem to help for a bit, but not long term.

I plan on changing the fuel filter tomorrow. I don't know if this is the problem or not but I will update after it is done.

Thanks in advance for any advice. I'd really like to get this figured out because I feel like it will burn out my starter if I let it continue.

 

Just got done with the fuel filter change. It was very needed, but the starting trouble still seems to be there. I bought some spark plugs and will change those tomorrow, just didn't have time today. Seeing as how I just bought the truck and it is right at 100K miles, I'm trying to replace everything that I think would need changing. Thanks for any advice.

 

Read up on the spark plugs, brown coils means you have the newer 1 piece, black means the old breaking in half 2 piece. Could be a lot more work than you'd think if you have the original old style with that many miles.

Wouldn't hurt to get a fuel pressure reading to know what the pump is doing, then again to see if the line is losing pressure. One way to check that would be to cycle the key 2 or 3 times @ 5 seconds each before you start it to pressurize the line.

 

When you say "full cycle and stop trying" are you saying the engine is not turning over properly or turning over but not firing?

 

When I turn the key it will just try to start for about 5 seconds and if it doesn't turn over it will stop trying to turn over all together and I will have to turn the key again.

I don't know if this makes sense or not, let me know if there is anything that needs further explaining. I'm trying to read up on the spark plug topics as much as possible before I change them. I'm hoping that is what the problem is.

 

If I'm understanding this correctly you have a problem with the starter not turning the engine over properly.Is there a clicking when this happens?
If it is the starter or starter circuit it could be just a bad connection at the battery,starter,relay or engine ground ect.or the starter,battery,alt or relays could be faulty.

I would fix the starter problem,if this is the case,before doing anything else.

 

There is no clicking when it does this. The reason I don't think it's a battery or starter related issue is because using premium over regular fuel seems to make a difference for the better.