I know this answer, partly, since I have tried it. I have a non PATs key I carry sometimes for my F150. I had it created for a $1 at a discount key house, it will open my truck doors and get me into the cab, but it won't start my engine. Just out of curiosity I have tried starting the motor with it. It will fit into my ignition lock, and it will crank the engine quite well - but the engine never starts.
That key once saved me some trouble when I lost my regular PATS key at a shopping center. I was able to remove valuables from my cab so that I could return home and get my other set of keys.
I want to do a compression test on my cylinders. It appears that the ignition and fuel system are cut off when I use a non-PATs key to crank the engine - and this is just the situation I want when I run a cylinder compression test.
Does anyone know for sure, if this is the case?

 

Yes, a non pats key is recognizes as illegal and prevents the motor from starting by inhibiting the fuel.
It is supposed to work that way or it would not be a Theft protection system worth the effort to be there.
Your PATS key has a chip the system recognizes. The one you got for a $ does not.
Good luck.

 

Does the ignition system still fire when the ECM cuts off the fuel supply? I hope using my non-PATS key would also inhibit the spark - that would greatly simplify testing cylinder compression on this model.

 

It really does not make any difference about spark.
You have to remove the connectors off the coils and remove the coils and spark plugs to open all cylinders to air before testing compression on each cylinder.
You also must open the throttle to allow air to be drawn in during cranking.
If your further concerned, remove the fuse that supplies both the coils and injectors.
Good luck.

 

Now you have my curiosity raised. Why would you need the spark inhibited to test compression? If there is no fuel it won't run, it will just crank.

 

Everything I have read about testing compression has said you should somehow disconnect (or bypass) the power supply to the coil (or to the equivalent in modern systems) to prevent the unnecessary generation of 50,000V spark voltages that would otherwise find their own paths to ground. Perhaps there is even a possibility of the stray sparks blowing holes in insulators or otherwise damaging engine electrical parts, for no good reason, since spark and fuel are not essential to measure cylinder compression. I'm not an engineer, just my opinion.
I bought and used a cheap (HF) inline spark detector last night on my F150 as it was getting dark out. Plug #4 had a nice spark detected, along with a bright side spark coming from where the detector wiring tried to connect to my plug. 2 sparks for the price of one!. On further tests I made a point to really bear down hard on the connection and I saw no more stray sparks.
I asked my original question because I thought the cranking of my engine with a non PATS key would have had the same effect as disconnection of power to the coil during the cranking process.

 

You have a 2001 with 8 coils.
You remove the coil connectors first, then remove the coils out of the holes.
Then you remove the plugs.
There will be no spark when this is all done.
You must remove all the plugs for a compression test to be meaningful.
So I might as well ask what it is I don't understand about this if you keep asking.
Even if you have a V6, removing the connectors from the coils will prevent spark.
I will accede that under certain circumstances if you pull plugs and crank engine with fuel and spark present that you are inviting fire from gas pumped out of the plug hole.
That is the basis of the warning as it does not address a non Pats key but for overall safety on any engine and situation.
If you know you have no fuel and spark it does not exactly apply.
Are you under control of the situation or not?
Good luck.

 

Those are good points. That's why I asked. I didn't see a reason, now I do. Thanks!