Okay let's see if I can Explain This one!
2001 F150 SC Lariat 2wd 5.4L 254,000 miles
About 2 weeks ago my wife complained that the gauges would peg out every time she started the truck. sure enough they were! There was no service lights staying on so..... instrument cluster issue no problem drive it I'll look at it later. 2 weeks go by and the truck starts in the driveway no problem warms up runs for all of thirty seconds dies and will not start. I have checked spark, crank position sensor is fine,battery is fine all cabling is in good order. I had a buddy bring home his Snap-on scanner and program keys and check the truck and there are no codes in the system! I have come to at loss on this one. there is pressure at the exhaust pipe when it turns over so, I haven't done a compression test and have ruled out the timing chain.

suggestions please!!!

 

the gauges pegging is normally a loss of voltagae thing... if you disconnect the battery and reconnect, the first time you start, the gauges will spike. If it happens from time to time, it normlaly means you have a battery or ground cable problem... Now the truck cranks i assume, but will not start ? If it ran for 30 seconds, i wonder if it ran out of fuel. Turn on the key, do you hear the fuel pump at the tank running for a few seconds? Look at the fuel line going to the injectors. THere is a schrader valve on the line somewhere. Push the needle in the center and see if it shoots out gas. You should have 20-30 pounds of pressure just setting there not running.

 

It has a full tank of fuel and check the fuel pump it humming along and doing it's job. Plenty of flow and pressure.

 

Maybe not enough voltage to the PCM. I will inspect the cables a little more thoroughly!

 

how did you rule out things like the CPS and timing chain?

 

The scanner reconized RPMs while turning the engine over, which is generated by the CPS. The timing chain only by the fact that I still have consistant flow from the tailpipe when turning it over.

 

...How old is your battery? If you have a dead cell in the battery, It can cause issues like your saying. I have seen batteries meausre 12 volts, and still have a serious voltage drop.
Rich

 

It's a 2 year old Orbital from Napa.

 

didnt wanna sound like i was questioning your knowledge, just alot of people come on here saying they did things, yet have no idea what there talking about.

 

No worries. I usually sit down and ponder the issue for a couple of days and have an answer for myself If it's a mechanical I don't have a problem if it's totally electronic issues I'm lost.

 

you need gas and air... and fire at the right time to run. sounds like you got gas to the rail, but cant be sure if injectors are working, or spark plugs sparking, or timing correct. I think i might have a tendance to shoot a small shot of ether into the intake port while cranking and see if you get it to fire. If not, than you are back to plugs sparking and timing. I dont know if you can pull a COP and put a plug in the end and ground it while cranking to see if you have spark ?

 

I rescanned after draining the battery cranking it and got low voltage to PCM message. After closer investigation I found the neg. Terminal down by the crossmember to be almost corroded into where something had rubbed on it for quite sometime. After a little whittling, a coupling and shrink tubing..... It starts runs and gauges no longer reset on starting! The stupid stuff that can go wrong will drive you crazy!
Thanks for all the help and I hope to get another 250,000 out of her.

 

Good to here you used shrink tubing. Most would use an open end connector and about a year down the road would have the same problem all over again if living in a winter climate where salt is used. I see your from Texas but where I come from nothing short of sealing heat-shrink will stop salt corrosion from ruining a wiring repair. I watch numerous car shows such as Horsepower TV for example and see wiring connected with open connectors or quick connects and just shake my head. They wouldn't last one winter in my climate conditions.

 

Sounds like a fuel pump to me. Just because you hear it runnung dosen't mean it's putting enough fuel into the motor. Had the same problem once. I could hear the fuel pump running but the fuel pressure wasn't there.