03 Sport Trac heat related relay problems?

[saundo]

My 03 Sport Trac 4WD is developing quite the cantankerous side recently, and I am looking for feedback whether I'm on the right track or not.

It's my daily driver, and I've put almost 60K miles on it. Recently had a cracked PCV and clogged fuel filter replaced, and then had the following experience about a month ago:

Drove from office to local McD's for dinner with the family, 35 miles, no problems.
Was at McD's for maybe 30 minutes, then drove another mile to my son's elementary school for orientation. Truck sat for maybe 90 minutes on a slight downhill slope.
Refused to start for another hour, and then after 5 turns of the key by the tow truck driver who was about to tow me to the dealer, started right up, and ran like a champ until tonight, when basically the same experience.

Inertia switch was tripped, but didn't make a difference until the truck had sat for an hour or so and cooled down, and then it started right up. Could hear the fuel pump click to pressure. Swapped the fuel pump relay out, no difference.

At this point, I'm stumped. I think it feels like vapor lock, possibly at the injectors, but I also think it might be a relay problem? Really don't think it's the fuel pump, as it's been reliable to date. Any insight greatly appreciated.

 

[ncranchero]

Inertia switches are problems, they overheat, they get kicked. Why would it have been tripped?

When it won't start can you hear the fuel pump whirring when you turn the switch to "ON"?

Vapor lock is not a common problem on these or any fuel injected vehicle that I'm aware of. More likely fuel pressure regulator/sensor or fuel pump driver module.

 

[saundo]

Inertia switches are problems, they overheat, they get kicked. Why would it have been tripped?

When it won't start can you hear the fuel pump whirring when you turn the switch to "ON"?

Vapor lock is not a common problem on these or any fuel injected vehicle that I'm aware of. More likely fuel pressure regulator/sensor or fuel pump driver module.

It's a good question, typically my truck has me in it, however the Boss was in the co-pilots seat yesterday and might have kicked it. I reset once, right after I figured out that it wasn't going to crank, but not since.

It really depends on the fuel pump sound situation. As I understand it, the fuel pump will only pump if it's not up to pressure. I think it is, I just think that there's something else going on!

I swapped the relay for an unused and that didn't make any different. Letting it cool down for another hour meant that it fired right up when I got back in it. I'm wondering if it's some kind of injector heat susceptibility or even injector fouling that's at play here.

Thanks for the reply!

 

[hotjr001]

Hi, our sport trac may have the same problem that you described on this post. Did you ever get it resolved?

 

[saundo]

update; apparently solved

In the end, after testing all the way from the fuel pressure rail to the inertial switch and being all clear, we dropped the tank and replaced the fuel pump. Inspected the wiring as far as we could and couldn't see any obvious problems that might have contributed to this.

For the record, we also replaced the fuel pump and a cracked PCV hose prior to this, which were causing overlapping problems, but I think the 03 OEM fuel pump just finally gave up after 142K miles.