The test is to attach a pressure gage to the fuel rail test port.
With engine running apply vacuum to the regulator and see if the pressure changes about 10 psi +/- from about 40 to 35 psi +/-.
The test you did was to see if the regulator diaphram would hold vacuum, not allow gas to leak into the vacuum hose and see if the regulator is capable of pressure change.
Good luck.

 

I thank you Bluegrass for your help and owe you an apology.
I realized only yesterday that the first thing I did was to disconnect the battery and redo the chassis grounds. I accidentally erased all codes.

I replaced spark plugs and wires. Pickup is running now. Out of 6 plugs 4 were black. The engine probably was running rich. I will drive the pickup for a few days and check the codes. Thank you, again.

Fuel pressure regulator checked out okay. The vacuum port was holding vacuum - no torn diaphragm.

 

The pickup now has new fuel filter, new plugs and wires. Engine runs fine. No Check Engine Light
Error code P0102 Mass Air Flow Circuit Input Low
Scanner readings: MAF 0.03 Coolant Temp 100 F (engine run only a minute or two) Short Term Fuel 11
I am not sure if the sensor is getting 12V or not. I need to get a pair of penetrating probes. Will report back.

 

You may need a new MAF.

 

You can use stick pins for probes. Those new shirt type pins. Patch the probe holes w/liquid e-tape.

Also, you should pull the MAF connector and check continuity from about 6" back on the harness to the connector pins. Wires have been known to break inside the insulation in this area , unfortunately. Man I hate that.

Anyway, flex/twist the harness while checking. Sometimes the wires can still touch stationary making for an intermediate problem. This can result in hair loss.

 

Thanks. Will check the wires this evening.

I am just curious. There is another sensor between MAF and throttle body. It has a 2-wire connector. What is the part?

 

IAT sensor.

Make sure ALL your MAF connectors are connected.

 

MAF gets 12 V power but no signal output. Same as scanner result.
Removed the 1' wiring between MAF connector and chassis connector. Continuity checked out right for all 4 wires. Time to replace MAF sensor. Thanks for your help.

IAT. I didn't know such a thing existed. Thanks.

I have another code P0453 Evaporative Emissions Control System Pressure Sensor High Input, meaning, Fuel Tank Pressure Sensor High Input. It is directly mounted on the fuel tank. Impossible to reach without removing the fuel tank? Again, wiring fault is a possibility.

EDIT: MAF replaced. Now reads 8-9 g/sec and goes up with acceleration. THANKS TO YOUR HELP. It's been much assuring to me that I have someone to talk to and that they know the vehicle. Pls advise on p0453.

 

Reset the KAM first, since the MAF was replaced. See if the 453 comes back.

 

It is a hard code, reset after first trip. I will have to crawl under and check wiring/connector. I searched for P0453 and found your older posts. I also read the shop manual. But it doesn't show pinout of the fuel tank pressure sensor.

Repair reported in a separate thread: https://www.f150online.com/forums/19...-question.html