* Compression: Low compression in one or more cylinders will prevent starting even with spark and fuel. A compression test is crucial here. Worn rings, valve problems, or a cracked head can all cause this. The "wants to start" symptom suggests it might not be *completely* lacking compression, but significantly reduced in one or more cylinders.
* Timing: The ignition timing could be significantly off. If it's way retarded (too late), it might crank but not fire properly. A timing light is needed to verify this. A distributor issue (worn rotor, cap, or faulty pickup) could cause erratic timing.
* Fuel Delivery Issues (subtle): While you say you have fuel, the *delivery* might be insufficient. This could be a clogged fuel filter, weak fuel pump (not providing enough pressure), or a problem with the fuel injectors (clogged or not atomizing the fuel correctly). A fuel pressure gauge is needed to check this. Listen carefully; a weak pump might make a faint whining sound.
* Vacuum Leaks: Large vacuum leaks can disrupt the air/fuel mixture, preventing proper combustion. Inspect all vacuum hoses and connections for cracks or looseness.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the position of the crankshaft. A faulty CKP sensor will prevent proper ignition timing and firing order, resulting in a no-start or hard-start condition. It's a common failure point on older vehicles.
* Ignition Module: This is the "brain" that controls the ignition coil and spark distribution. A failing ignition module can cause intermittent starting problems.
Troubleshooting Steps:
1. Compression Test: This is the *most important* first step. A low reading in one or more cylinders strongly suggests a major engine problem.
2. Check Fuel Pressure: Use a fuel pressure gauge to measure the fuel pressure. It should be within the specifications listed in your repair manual.
3. Inspect Ignition System: Visually inspect the distributor cap, rotor, and spark plug wires for damage or wear. Replace them if necessary.
4. Timing Check: Use a timing light to verify the ignition timing is correct.
5. Vacuum Leak Test: Listen carefully around the intake manifold and vacuum hoses for hissing sounds indicating a leak. Spray a carburetor cleaner around suspected areas while the engine is cranking; a change in engine sound indicates a leak.
6. Check CKP Sensor: This can often be tested with a multimeter, but a proper diagnostic tool is best.
7. Ignition Module: Check for any obvious signs of damage to the ignition module. Testing this component usually requires a specialist tool or access to diagnostic equipment.
If you're not comfortable performing these checks yourself, take your Ranger to a qualified mechanic. Trying to diagnose these issues without the proper tools and knowledge can lead to further damage or wasted time and money. Remember to always consult a repair manual specific to your 1988 Ford Ranger 2.9L V6 for proper specifications and procedures.
