Hey ya'll
I just bought a new motor for my 2000 f150 5.4. My question is after I hook everything up(meaning fuel injectors and eletronics) how does the computer know where the new engine is set at? Or what I mean is if the number 3 cylinder is coming up how will the computer know when to inject or set the spark plug to fire? I know when I took the old engine out number one was at TDC or very close to it. How will the computer know where the engine is set at? I'm just a shade tree mechanic.

 

Very good question;
Here is the answer.
The crank sensor sets the reference crank position for the PCM to work from.
The toothed wheel has a special spacing in it's tooth sequence to act as a time reference. Being fixed to the crank it never changes.
From that the PCM now has a reference for 'firing order' as built into the program.
The actual cylinder ignition 'timing point' being variable, is a computer ...'derived function'.... determined by temperature, RPM, and throttle opening and in some other special cases.
With this setup there is no need for a distributer, only coil control from the PCM in whatever form it is designed, 4, 6, 8 or 10 cylinder configurations..
.
Fuel injection timing is done from a reference as well but from the camshaft position. This must be done in this manner to reference intake valve opening point so the injection takes place when the intake valve is open on the intake stroke and well before ignition happens in a closed cylinder under compression. On the front of one head is the cam position sensor.
The cam gear has an surface point that passes by the sensor to generate a output signal to the computer for injection timing reference.
Injection timing only varies with engine RPM speed but the valve to injection point 'relationship' never changes.
Amount of fuel injected is a 'derived' function much like ignition timing that controls injector open time called pulse width control.
The compute speed is quite fast to handle all these functions in real time.
Bet your sorry you asked.
Good luck.

 

not really I just learned a lot. So, after all I don't have to do anything the computer will get its settings from the sensors. thanks for putting my mind at ease.

 

The computer has a 'base' program from which to operate from.
At first cold start the idle goes high depending on the temperature.
All tables are back to their normal base design and begin table alterations (learning) based on sensor and operating inputs from that point on until a stable moving average is attained.
At the same time, all diagnostics are launched and run to completion.
If any faults are detected a code is set and that specific test is left incomplete and turns on the CEL.
This sets a code 1000 until the all diagnostics pass.
If battery is removed anytime after, this causes the program to revert back (reboot) to the base tables again so the learn cycle starts all over again as well s all diagnostics.
Good luck.

 

For initial start, I'd pull the fuel pump fuse and crank it over for at least 15 seconds to build up oil pressure. A dry start on a new engine can be painful.

 

Even if he just turns it over the engine is dry for most of that anyway. Plug and play. Plug everything in and start it. If the engines all good everything will be fine.

 

There's a lot less pressure on all bearing surfaces when turning over using the starter than when actually running at cold idle speed. This is one "old school" principle that is still valid today. Way back in the day I always pulled the coil wire and cranked for 15 seconds before starting a new engine.

 

Well in the old days I would prime the engine from the oil pump drive shaft. Used to be before you put in the distributor you could drop o socket on the oil pump drive shaft and spin it up... I wouldn't worry about it to much You should have oil pressure in about 15-20 seconds.. The engine should have enough lubrication from the machine shop. But if it makes one feel better by all means pull the fp fuse..

 

Yep, that was a very good way of doing it. Do you really trust the shop to use assembly lube and properly prelube the engine? How long after assembly was it sitting around?

That 15 to 20 seconds can be critical.

 

You can also floor the gas pedal and it will kill the injectors. I doo this when I remember at oil changes. Don't need to disconnect anything.