clintandrew

I have a 1998 f150 xlt, 4.6L v8, single cab, short bed, motor is factory spec. Over the last year I have had an intermittent starting problem. Every once in a great while I will drive it somewhere, shut if off, come back out and it won't start. It cranks over, it gets fuel, it gets spark, but it acts like the timing is off, yet the timing is not off. At first I decided to switch around the maxi fuses under the hood and it would start right after. So whenever it did this I would just switch the fuses around and be on my way. Today it was about 80 degrees outside, the truck started fine, drove into town, shut it off, came back out from the store and it started fine, I returned home and let the truck sit for about a half hour then went to leave and it wouldn't start again. Same symptoms and still getting spark and fuel. I switched around the fuses and it did not work this time, I could not get it started! So instead of burning up the starter or anything I decided to leave it alone since it was in my driveway. Hours later and 15 degrees cooler outside I go out to check if it will start... perfect start! Ran perfect... does anyone have any idea what is causing this??? I'm confused, the Ford dealership is confused, no check engine light when it runs. Any help would be much appreciated!!

clintandrew

For anyone who reads this, it did it again today so I went and bought a crank position sensor (since it was the cheapest part to replace) and it fired right up with the new one in. Hopefully that did the trick.

hamchuck

It sounds like I'm having the same issue. Is it still holding up okay?

clintandrew

I changed the crank position sensor and it stopped for a couple weeks, then it did it again. Went ahead and dropped the fuel tank and replaced the pump and ever since I changed the pump its been perfect. It was weird though because you could hear the old pump priming.

hamchuck

Here's how my mine went down, for general knowledge to the community. The starting problem evolved to stalling at stop lights also. I called around to price a fuel pump and happened to talk to an experienced Ford mechanic. He asked me to describe the problem and recommended I bring it in so he could check the fault codes. The gist of it is, my alternator was bad, and was producing the whining noise that I'd though was a fan clutch. He figured it might have been producing enough electromagnetic interference to screw up the ECU.

His day job is at a diesel truck repair shop in Tucson. They also do gas engines, so I brought it there. He re-programmed the ECU, replaced the alternator, and now it's running just fine.

imp

Hearing the pump running ain't enough. I had one that pretty much did things just like yours. Started right up first thing, then later very long cranking time to start, or did not start at all. Sat awhile, then started. As this got worse, I measured the fuel pressure at the rail. Pre-crank, 2 second priming, it went right up to spec. Started, then dropped 20 psi, idled poorly. Given throttle, it perked right up.


Bottom line was, something was affecting the fuel pressure. Before dropping the damned tank, I replaced the fuel filter. Problem solved. It seems the **** which accumulates in the filter can sometimes shift around in it, causing the pressure drop across the filter to vary, from not enough to be noticeable, on up to keeping it from starting. Best guess I can come up with. imp