After thinking for a few - it seems your most probable fault lies in fuel not getting to the engine - most probable would be fuel solenoid not engaging or blown fuse to the solenoid circuit.
Here is how you can isolate whether fuel issue or spark issue (it can also be a timing sensor failure - but that is harder to diagnose).
From Grok:
Can starting ether be used on an F-150 with fuel injection to test whether the engine is getting spark and may be fuel starved ?
Yes, starting ether (or starting fluid) can be used on a fuel-injected Ford F-150 to test whether the engine is getting spark and may be fuel-starved, but it must be done cautiously and correctly to avoid damage. Here’s how it works and what you need to consider:
Why It Works
Starting fluid is a highly volatile substance (typically ether-based) that can ignite easily in the presence of a spark, even if the fuel system isn’t delivering gasoline. If the engine briefly fires or runs for a moment after spraying starting fluid, it indicates that the ignition system (spark plugs, coils, etc.) is likely working, and the issue is probably fuel-related (e.g., fuel pump, fuel filter, or injectors). If it still doesn’t start, the problem could be ignition-related or something else (e.g., a sensor issue).
How to Use Starting Fluid on a Fuel-Injected F-150
Locate the Air Intake: Find the air intake tube or throttle body, typically near the air filter box or where the intake hose connects to the engine.
Spray Sparingly: Remove the air filter cover or access the throttle body. Spray a small burst (1-2 seconds) of starting fluid into the intake while the throttle is slightly open (you may need an assistant to hold the gas pedal slightly or manually open the throttle plate).
Attempt to Start: Immediately try to start the engine. If it fires briefly or runs for a few seconds, the engine is getting spark, and the issue is likely a lack of fuel delivery.
Observe Results:
Engine Fires Briefly: Suggests the fuel system (pump, relay, filter, or injectors) is the problem.
No Response: Indicates a potential issue with the ignition system (spark plugs, coils, or wiring) or another component like a crankshaft/camshaft position sensor.
Precautions
Use Sparingly: Too much starting fluid can cause excessive combustion pressure, potentially damaging pistons, rods, or other engine components, especially in a fuel-injected engine with precise air-fuel ratios.
Avoid Overuse: Repeated use can wash oil off cylinder walls, leading to wear, or cause a backfire that could damage the intake system.
Ensure Proper Ventilation: Starting fluid is highly flammable. Work in a well-ventilated area, away from open flames or sparks.
Check Compatibility: Most Ford F-150s with fuel injection (common since the late 1980s) can handle a small amount of starting fluid, but confirm your model year doesn’t have specific restrictions (e.g., some newer engines with direct injection are more sensitive).
Don’t Use with Glow Plugs or Diesels: If your F-150 is a rare diesel model (e.g., Power Stroke), do not use starting fluid, as it can cause severe engine damage due to glow plug ignition.
Additional Notes for Your Situation
Since your F-150 was running fine on Sunday but now cranks strongly without starting, using starting fluid is a good diagnostic step to confirm whether the issue is fuel delivery (e.g., a failed fuel pump or relay, as these are common in F-150s). If the engine fires with starting fluid, focus on checking the fuel pump (listen for a hum when the key is turned to “on”), fuel pump relay, or clogged fuel filter. If it doesn’t fire, inspect the ignition system (spark plugs, coils) or scan for codes with an OBD-II scanner to check for sensor issues.
If you share the model year of your F-150, I can provide more specific guidance about the fuel or ignition system quirks for that model. Would you like me to search for additional F-150-specific troubleshooting tips on X or the web to refine this further?
fuel injection diagnostics
common F-150 issues
Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good ...
| 
