I'm scatching my head on this one. The CEL came on a week or so ago with a P0401 code but I had not gotten around to fixing it. A couple of days ago my 2002 4.6 (118k miles) would not start after driving it from home to the store, approximately 2 miles. I had my son pick me up, grabbed the code reader and went back to the truck. It showed only the P0401 code with no pendings. I made sure the vacuum lines were all on then tried to start it again and it fired up.

Yesterday I went through the EGR system trying to find out where the code was coming from. I checked the following:

EGR valve - holds vacuum and there is very little carbon build up in the valve or in what I can see of the intake
EGR vacuum regulator - harness has voltage and resistence is within spec
DPFE sensor - voltage checks OK on both sides of the harness

I cleared the code and drove it for several miles with some stops in between so the monitors could cycle. The code reappeared and there were no others pending. I turned off the truck and decided to look at the system this morning.

This morning the truck will not start and I haven't touched anything under the hood. Any ideas?

 

If you apply vacuum to the EGR valve when the engine is running, does the idle drop? If yes, good. If no, clean the valve and all tubing and try again. If still no, replace the EGR valve.

If that's all good, check all hoses connected to the DPFE, you may have a crack or a blockage. If that's all good, replace the DPFE with an OEM Ford part.

 

Thanks GLC. The truck finally started (I have touched nothing since it would not start this morning). I turned it off and restarted twice and now it will not start again. Will something in the EGR/vacuum system cause the truck not to start or not to start intermitently?

 

I dunno - but I might suspect the DPFE.

 

Try changing the cam sensor at the drivers side front cover. An engine will still startup approx. 50% of the time with a bad cam sensor. Good luck

 

Thanks, Dynotech; I'll take at look at the cam sensor and see if there is a diagnostic test I can run before changing. I am going to check the fuel pump as well since it seems a pump going out can function at some times but not others. The truck started up several times in a row last night and then failed to start again. This intermittent stuff drives me nuts trying to fiqure out where the malfunction occurs

 

Changed out the cam sensor and nothing is different with the starting problem. It started after 8 - 10 attempts over 2 hours. I changed the DPFE sensor which fixed the CEL P0401 code. Now it won't start again and no codes are present or pending. I hate intermittent problems.

I am starting to think it may be the fuel pump. I had a friend with a Chevy that had a smilar problem and it turned out the fuel pump would power up sometimes and not power up at other times. I'm looking to purchase a pressure guage I suspect.

 

Maybe the inertia switch is getting flaky?

 

Before I went to a lot of trouble and expense, I'd check the starter relay switch on the firewall. Had a similar problem a while back with a '98 F150 4.6L. I swear it would start for anyone else, but when I got in it--no deal. Even Crossroads Ford couldn't track it down (I live in Frankfort--howdy, neighbor). There's a pretty simple method of troubleshooting the problem I posted a while back if you search this thread for The Vinman, you'll probably find it. Stupid 14 dollar switch.

 

A starter relay problem would cause a "no crank" symptom, not a "cranks but does not start" symptom.

Get the fuel pressure gauge on there. It will eliminate guess work and will identify whether or not your problem is fuel delivery related.

Steve