I have a 99 F150 work truck. 148k on the truck, 40k on a remanufactured 4.6engine.

If the odometer shows the mileage when I turn the key on, the engine will start immediately. If the odometer shows only dashes (-), the engine will crank like crazy but will not start. This is an intermittent problem.

I have cleaned the aircleaner and replaced the fuel pump and filter. No change.

Thank you in advance for your help.

 

I don't know exactly what would cause this, but you need to bark up the right tree. This looks like an electrical/electronic issue, not an air or fuel issue. It sounds like when the odo is showing dashes, something is grounded or open that shouldn't be, or some sort of sensor is dead.

I may be wrong, but hopefully someone knows exactly what that means.

 

Is the truck equipped with PATS, if it is, it may be a PATS problem.

 

Clean and check all connections from the battery to the cylinoide then to the starter. could also be the cylinoide is failing. might just replace it. $10 at autozone.

 

Joshmac4.6 hit the nail on the head. The PATS module is located in the Instrument cluster....dashes on the cluster are always a bad sign of either a blank PCM or a failed cluster which would means the PATS is not working.....It will crank like there is no tomorrow but will not start. Do you have access to a scanner that can read codes other than generic OBDII codes? How about the theft lamp when this happens? Is it flashing?

On the PCM side you need to make sure all the grounds are secure and making good contact...no corrosion etc....not just the big battery ground but all the smaller grounds throughout the engine compartment....

glc mentioned a bad sensor, a short to VREF could cause PCM troubles as well, you could try unhooking various sensors when this happens one at a time to see if there is a problem sensor causing an issue. You will set a code when you try this though and the CEL will come on. I'd be leaning more towards a failed cluster/PCM problem on this one.

 

this may sound stupid but if you have the keys with the chip in them, is the key all the way in? mine will turn over but not start if the key is not all the way in, and there is very little difference in the feel of it when not in all the way. just a stupid moment that I've had so I figure I'll share my experience. good luck

 

Thank you for the input. This information will be very useful, but at the risk of sounding stupid, I don't know what the PATS module is. I also do not know what PCM, VREF or CEL stand for.

Where can I find this information?

 

Sorry, I'm not good at breaking things down sometimes...I'm used to thinking these terms all of the time...
PCM- powertrain control module or the engine computer

PATS-Passive anti theft...the chip in your key is read by this. It is part of the instrument cluster. There is a tranceiver ring around your ignition lock cylinder that reads they chip in the key and sends it to the module...if a valid key code is received then the engine computer enables the start. If they key code is invalid it will still crank but not start.

CEL- check engine light

VREF- 5 volt reference voltage sent by the PCM to the sensors on the motor.

I don't know of any good online references other than what I have access to...I'm sure somebody around here knows though....hope this helps a little

 

Ford Tech 1- I really appreciate the explanations. Thank you for taking the time.