[bootshowl]

Got a 99 F150, 4.2ltr V6, that sometimes just won't start. Seems to happen when I've run lots of errands and started it several times. I'd say fuel pump, but let her sit awhile and she'll fire back up and run ok. Been stranded a couple hours twice last summer, then all winter no problems. Today it's up in the 70's, and she's done it again. Intermittant, and seems heat related; but not running hot by the gauge. It reminds me of the old days when a car would vapor lock.
Anyone got any ideas? Thanks.

 

[handyronokc]

I had a discussion with an acquaintance, who had an Explorer around that year, ( with that problem ) He found the problem at the fuel pump relay in one of the electrical boxes under the hood.

 

[bootshowl]

Thanks Ron. That makes sense too, as I've seen relay coils in other devices that will break down when hot.
I let her sit where she was till after sundown, and she fired right back up. I'm pretty certain if the fuel pump was failing it would just fail and be all she wrote.
Anyone else got any ideas please post em. This is one of those things that is frustrating, being intermittant, and the dealer charges bout thousand an hour to do the same thing we would do, LOL. They just have nice lil work uniforms ta wear......and the poor folk working there probably have to pay for their own uniform rental too; and only make a fraction of the rate charged....
I guess I'm stubborn, but hate to give money to a rich man.
:smile2:

 

[gottagetabigun]

had an old chevy would do that when the weather was warm. turned out to be the starter selnoid.

 

[Mike81]

So it turns over fine and won't start? Or it don't turn over??

 

[Ecfool]

one thing to check is does it have spark when it wont start? If not it may be ignition module, here is sunny hot as hell california we have a big problme with the Ford TIF ignition systems module on side of distributor will fail when it gets hot cools down and gets fire again. Also if it is module go ahead and change pick up coil in distributor as the plastic grommet where module fastens to it will deteriorate and crumble when you unplug module.

 

[bootshowl]

Yup, she cranks good. Might hit a lick or two then, strangles out. Just like she's fuel starved. Then eventually, if you wait long enough: she fires up just like the good lil truck she is and runs just fine. I've waited up to two hours or had it just fail for a few minutes, then start, like it was a gremlin or something. Last year when it went for two hours I was far away from home, and the battery was starting to go down, cranking slow, as I tried it every 10 mins. or so, then fired up, charged up, and down the road I go. Then it ran fine over the fall & winter, and today as the weather warmed, she's started it again.
I'm gonna check the fuel pump relay first.

 

[psychomekanik]

The next time this happens. have someone tap on the tank with a hammer while your cranking it. if it starts right up, your fuel pump is bad. the sure way to tell is to put a fuel pressure guage on it. does it build to spec, and hold with the engine off? slow to build pressure? even if it's running right, if you know what to look for you might find the problem with a guage. slow to build pressure is usually a filter issue. dont hold pressure is usually the check valve in the pump. Everything check ok? block off the return. (deadhead) it should spike up to at least twice the spec. which is 35-45. key on engine off is usually around 40-45 engine running is around 35psi.

 

[willcat]

we have seen a relay be the problem more than the pump on these, they are all the same, when it does it again locate the fuel pump relay & change itout for the wiper relay see if it starts, if not I would think that ur fuel pump is vapor locking!!! Happens all the time around here when we have a weather change & u have a weak pump... more often than not it's the relay though, hope this helps
when it happened to my 04 f150 4.6 it was the pump, but we had about a 40 degree weather change from cold to hot & the pump vapor locked. I waited about 30 minutes & it cranked right up, but it was under warranty so I had them put a new one in it @ work just to be sure!!!!

 

[bootshowl]

I put in a new fuel pump relay and also replaced the fuel in line filter. Pretty sure the darn filter was the original from the assembly line....it was heavy compared to the new one, and could hardly blow thru it, LOL.
Hope I'm good. Thanks for tips guys.
"Remember, I'm rootin for ya, We're all in this together."
I put a lil piece of duct tape on the relay box, just for luck.
:smile2:

 

[bobs bait]

i had a dodge 1500 with that problem and it turned out to be the fuel cap was losing pressure would of spent a ton on it but a buddy told me to try that first and it worked