I have an 03 v6 f150. The last three weeks it has been nit starting all the time. I had it towed to the mechanic. The opened up the air filter compartment and it started. Filter was a bit dirty but not clogged. They changed it, cleaned the MAFS change the fuel filter and added a fuel cleaner. They started several times it was fine. I took how and it wouldn’t start again. Day later it started. Took it back to mechanic. No codes, started cold and warm. They suggested I take to dealership.
left there. Drove 15 minutes went into store for 20 minutes and wouldn’t start again. Tried several times giving 10-15 minutes between tries. Then opened up air filter compartment and it started, a little rough. Heard ticking, maybe lifter? Ticking eased up and went away as I drove it home. Any thoughts?

 

I'm the furthest thing from an expert but I'll share my experience with my 1999 XL 4.2l. I had an intermittent no-start condition similar to what you describe and then one day (of course in a grocery store parking lot), there was just no way the truck would start. As I expected, it turned out to be the fuel pump. I hope your issue turns out to be something less involved and expensive. I'm not sure why you mentioned the ticking (sure, could be a lifter) but I do not think that is related to the no-start condition. Best of luck!

 

I’d hate guessing at this, but it seems like nobody knows how to do no-start troubleshooting at those garages, either.

No diagnostics on fuel, spark and compression?

Im not sure how fussy this generation truck is, but many makes won’t start if there is no MAF signal. Sounds like that MAF or the harness has something going down with it and disturbing it wakes everything back up.

But, again, that’s a guess. I don’t know what it’s (not) doing when you turn the key.

 

It cranks over well enough just won’t start. I’ll look into the MAF thanks.

 

I was thinking fuel is pump too. Until the disconnecting the air filter allowed it to start. Thanks for your thoughts. Bike it’s not the fuel pump. Mines I t he gas tank.

 

It will bust off with virtually any sort of maf problem until the plugs are fouled black, so I would rule out maf.
The 2 most probable issues are fuel pump and eec power relay. Fuel pump may set a DTC, eec relay cannot. EEC relay issues can be partially diagnosed from the driver's seat when the truck refuses to start. On an '03 the symptoms observed by the driver will be the odometer displaying dashes, the red THEFT light will flash rapidly and the engine will turn over but not start. EEC relays do not fail while driving, only when a start is attempted.

If this is observed, I give you permission to stop diagnosing and install the $10 relay. If you want to be exhaustive, open the hood and just tap the top of the fuse box with the key still on. If this makes the eec relay close, you'll hear a couple of clicks and fuel running through the fuel rail for ~1 second. That would mean you need a relay. You could also check for power with a test light at the injectors and/or coils which are also powered by this relay. No power with the key on means bad relay.

My favorite course of action is to just swap the eec relay with the blower motor relay right now. If it was the eec relay, the no start won't happen again and, interestingly, bad eec power relays seem to work fine for the blower motor.

I won't go into fuel pump diagnosis since it's pretty well documented.