Intermittent crank no start

[Brettos]

Hi everyone, sorry for this being my 1st post and coming in as being needy.

I'm at my wits end with chasing this issue down where my Explorer cranks and cranks but wont start. Its hit and miss. Sometimes it will start up just fine and will start up multiple times with no indication of trouble. In fact when it does start, its within 1-2 cranks so it starts great, when it does. Other times, if its doing its thing, I believe I could just continually crank it until the battery dies or the starter burns up.
When its not starting, the way I eventually get it started is by stop cranking it and then cranking it again immediately, sometimes it will start up but sometimes I have to do that a few times.

Runs smooth and solid when its starts, no stalls, no fault codes ever pop up. Ive tested and even replaced the crank pos sensor, get a 3VAC signal. Tested the cam sensor, not replaced though, get about a 1VAC signal. Replaced fuel filter. Fuel pressure is around 45psi (and why did Ford feel they needed to omit a schrader valve on fuel rail on this year's model!) I've tapped into both the injector's and sparkplug's connectors with a LED and can see it pulsing when I crank the engine. Oh and I've moved the relays around under the hood thinking I may of had a flaky one, no help either.

Doesn't matter if the trucks been running all day or 1st start of the day, all random.

Its a 4.6l if that matters

I'm at a loss.

Brett

 

[dkl]

Sounds like a fuel pump going out, possibly the armature, worn brushes or thermal issue. Next time it does it, try the tap test, lightly tap the bottom of the tank with a mallet. Sometimes that will get you going but it won't solve the problem.

Also check the fuel pump cut-off switch (inertia switch) in the passenger kick panel to make sure it is working correctly. RA has a pretty good selection of pumps if that's what it turns out to be. Mine was replaced at about 100K miles, had all of your symptons.

 

[Brettos]

A bad pump doesn’t make sense to me in my case. How can it be showing good pressure and still not start?

 

[dkl]

A bad pump doesn’t make sense to me in my case. How can it be showing good pressure and still not start?

Mine also had pressure, at least when I was checking it. I also replaced the relays and checked the voltage coming out of the inertia switch. I had spark and no ECM codes. The position sensor and fuel filter seemed unlikely causes given my mileage and maintenance.

All random and it went on for almost six months. Towards the end it blew the 15-amp fuel pump mini fuse under the hood. I think I was draining the battery at that point.

It's probably a common problem and someone else here will chime in with their experience.

 

[Brettos]

Hmmmmm
Maybe I’ll just order a pump and replace it. I just hate the thought of replacing something that may be good.
Still cheaper than taking it to a shop I guess.

 

[dkl]

Hmmmmm
Maybe I’ll just order a pump and replace it. I just hate the thought of replacing something that may be good.
Still cheaper than taking it to a shop I guess.

Yes, it's frustrating. I was stumped and came to the conclusion that I had an intermittent electrical problem, a pinched or exposed wire. I pulled up the wiring in the kick panels, under the door sills and around circuit boxes, checked for power and continuity on everything I could. I had just finished replacing my wheel bearings and suspension and didn't want to hassle with it anymore. I gave up and took it to the neighborhood indie.

Once they had the tank out, they had me by the wallet. The installed an O-Reilly's Precision Pump and I was out the door, but it was very expensive. I think the pump that came out was a Bosch. Check around this site for other possible solutions, a lot of smart people here if you have some time.

 

[Brettos]

Follow up:
I hate when people fix something and don’t follow up. You have to put closure on stuff.
Anyway, the other day I parked the Explorer after driving it from work 40 miles, went out to start it and it would do nothing. Headlights were bright and didn’t dim at all when I tried starting. I checked all my wiring for corrosion, cleaned the battery cables. Still no start or and click of the starter. I climbed under and checked for battery at the starter, I had good battery right to the starter. Jumpered the terminals and still nothing.
Great I thought, now I have a starter issue along with whatever else I was chasing. Pulled the starter and bench tested it. It would barely turn!
Bought a new starter and now the engine starts EVERY time!
So as odd as it was, the starter was very very sloooooowly dying. Then just croaked. It’s odd because it seemed to crank fine this whole time but with the new one, the crank speed was quite a bit faster.
Glad to have this issue put to bed.
Brett

 

[Ron Gorman]

Solved. it's the electronic portion of the ignition switch. change the worn out ignition switch

 

[Fix4Dirt]

Solved. it's the electronic portion of the ignition switch. change the worn out ignition switch

thanks for giving a solution! and welcome!