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Will not start

Tiny
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  • MEMBER
  • 2001 FORD F-150
Two Wheel Drive Automatic 76000 miles

I went out the other day to go on an errand and when I turned the key to start it, it turned over fine but would not fire. No stumbling. Just the sound of a healthy starter turning the engine over. I took a shot in the dark and wiggled the fuel pump relay. Presto the engine started and worked fine all day. Next day the same thing occurred but this time wiggling the relay did not produce the same results so I removed the relay and promptly replaced it and then the truck started and worked fine all day. I then assumed a defective relay and bought a replacement and installed it. Next day I went out to test the truck to see if it was going to start and it did and I thought the problem was solved. WRONG!

I went out today and it will not start no matter what I do. I tried replacing the new relay with the old relay to see if that would have an effect and it didn't so I am dead in the water with no ideas. There is no "Check Engine" light on or any other indication of a malfunction. I have checked all fuses and the gas tank is 3/4 full.
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Saturday, November 29th, 2008 AT 8:23 PM

12 Replies

Tiny
DAVE H
  • MECHANIC
  • 13,384 POSTS
Thanks for the donation. Have you checked if the engine is/is not getting fuel to cylinders try cranking it over and then removing a spark plug. To check if we are getting fuel? Plug should be wet and smell of gas? Please repost with answer and could you also supply exact engine size of your vehicle
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Saturday, November 29th, 2008 AT 8:36 PM
Tiny
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The engine is the 5.4 Triton V8.
I cranked the engine and pulled a spark plug and it's dry.
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Sunday, November 30th, 2008 AT 12:20 PM
Tiny
DAVE H
  • MECHANIC
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When you first sit in vehicle. Make sure everything is turned off. Radio/heating etc. Put key in ignition and turn to ON. Do not try to start. Just ignition lights on. Do this a few times slowly. Do you hear a buzz noise for about 10/15 seconds? Also could you check fuse #10. 20amp. In underhood fuse/relay box.
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Sunday, November 30th, 2008 AT 2:00 PM
Tiny
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I did as you said and I could hear a buzz that lasted about 2 seconds that was coming from the back about mid-ships. I am assuming that is the fuel pump being activated? Fuse 10 is ok. If only it were that simple.
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Sunday, November 30th, 2008 AT 4:12 PM
Tiny
DAVE H
  • MECHANIC
  • 13,384 POSTS
So we now know fuel pump is working .. so if there is no fuel in cylinders on cranking then we are not getting injection .. try replacing CMP ..

Camshaft Position Sensor
A 3-pin Hall Effect type sensor or a 2-pin variable reluctance Camshaft Position (CMP) sensor is used. CMP sensor is used to determine camshaft position and to identify when piston No. 1 is at Top Dead Center (TDC) of compression stroke. CMP sensor signal is used by Powertrain Control Module (PCM) for synchronizing firing of sequential fuel injectors. Applications with Coil On Plug (COP) ignition also use CMP signal to select the proper ignition coil to fire.

Camshaft Position (CMP) Sensor (5.4L)On front of engine. See Fig. 3 .


http://www.2carpros.com/forum/automotive_pictures/266999_cam_4.jpg

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Sunday, November 30th, 2008 AT 5:45 PM
Tiny
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I put the spark plug back in and reconnected the coil for it and decided to see what would happen if I tried to start it. It started. Just what I need, an occasionally starting truck. A mechanics worst challenge and an owners worst fear because I'll never know when it will fail again. I think I'll take it to a garage and let them chase the problem. That is if it starts again tomorrow. I was hoping to find the failed part without going through and replacing them by trial and error and with it starting whenever it feels like it I will never know if I have fixed the problem till it won't start again.
I appreciate your help on this. I have learned a few things about the truck and I am more convinced than ever that I am out of my comfort zone with this problem.
Thanks again.
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Sunday, November 30th, 2008 AT 7:05 PM
Tiny
DAVE H
  • MECHANIC
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Out of curiosity which plug and coil did you remove? It could just be loose connection somewhere?. Have the mechanic plug it in to a diagnostic computer. It should tell him where the fault lies. Hope it starts in the morning for you?

Dave H
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Sunday, November 30th, 2008 AT 7:12 PM
Tiny
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As you face the engine, the first plug on the left (passenger side). Is that number 1?
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Sunday, November 30th, 2008 AT 7:16 PM
Tiny
DAVE H
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Yeah #1. I am of the opinion that it is the CMP. Not supplying a pulse to the injector circuit. This could be a faulty sensor or wire to the sensor. Sometimes they work when cold. And not when hot? Engines are 70% electrical sensors nowadays. Not like they used to be. Plug it in to a computer and it will direct you to the fault. They will start making us coffee soon I hope. Haha. Ask your mechanic to read the PCM. Let me know the outcome please?
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Sunday, November 30th, 2008 AT 7:30 PM
Tiny
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The last car that I had that I could work on was my '73 Volvo 1800ES. I sold it a couple years back and haven't had the nerve or desire to work on the newer cars that we have owned. Makes you techs a very valuable bunch.
I'll let you know the outcome.
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Sunday, November 30th, 2008 AT 7:44 PM
Tiny
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I took the truck to a local garage and they replaced the fuel pump and I have had no problems since. It was malfunctiong on an occasional basis and they diagnosed a pressure drop. Not the repair I had hoped for but we don't always get what we want. $600 poorer but it works.
Thanks for your help and ideas.
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Saturday, January 3rd, 2009 AT 7:09 PM
Tiny
DAVE H
  • MECHANIC
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Thanks for letting us know the outcome.

Happy new year and Happy Motoring

Dave H
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Saturday, January 3rd, 2009 AT 7:37 PM

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