I have a 99 Blazer LS 4.3 with no-start issues. It turns over but won't crank. The security light blinks when I open the door but goes out after putting the key in the ignition and turning it on. I can hear the fuel pump prime when I slightly turn the key to the crank position, but not enough to turn over, the fuel pump also runs for a couple seconds after I turn the key off. I'm no mechanic so I'm trying to rule out the passlock before diving deeper in the fuel system. I've had a few problems in the past with cranking but she always ended up firing eventually. I just changed the plugs and distributor cap last summer, so I don't think it's a spark issue. ALso, does being able to hear the fuel pump rule that out as well? Or can you still hear a malfunctioning fuel pump? I haven't checked fuel pressure yet.

 

Is the battery fully charged? (At least 12 volts)

You said you changed the cap and plugs... did you not change the rotor? or wires?

Fuel pump should run for about 2 seconds with key on engine off, and then another 2 when you turn it off.

Next step, fuel system diagnosis, would be here: https://blazerforum.com/forum/tech-a...agnosis-23038/

These are things I'd check, anyway.

 

If/when Passlock detects a theft situation, the security light will stay on, the engine will start, the PCM will disable the fuel injectors, and the engine will stall, usually within 2 seconds. Sounds like Passlock is not the issue with yours.

The only 100% accurate way to test a fuel pump is by checking maximum pump output pressure, leakdown rate, and regulated fuel pressure.

When you initially turn the ignition to the RUN position, (do not start the engine) the fuel pump should run for ~2 seconds and then shut off. The 2 second time frame when the pump is running is called "pump prime". When you turn the ignition to the OFF position, the pump should run for ~2 seconds after the engine shuts off.

Most auto parts stores rent/sell fuel pressure testers. It connects to the service port next to the distributor. Ignition ON, engine OFF, fuel pump running, (pump prime): Pressure must be 60psi to 66psi, (this is the regulated fuel pressure). Pressure must remain above 55psi for at least 10 minutes after the pump shuts off, (this is the leakdown rate). Post your results, if it fails either part of the test, further testing is necessary to pinpoint the problem.

 

battery is dead now, I'm going to jump it off and try again when my ride gets here. I changed cap, rotor, and plugs. Wires are still in good condition. I just pulled off the dist. cap and checked for cracks and moisture because it has been raining the last few days and it is still in good condition. Pulled a plug out and checked to see if it was sparking before I killed the battery and it's got a good blue spark.

As soon as my ride gets here I'm going to the parts store to get a fuel pressure gauge and a new fuel filter. The filter hasn't been changed in 40k+ miles, so hopefully it's just a clogged fuel filter.

 

Can't tell if wires are good just by looking at them. That's like looking at a swimming pool and trying to guess the water temperature They need to be tested on an oscilloscope. Checking resistance with an ohm meter is not near as accurate, but it works. Rule of thumb, with good quality wires, they should last 100K miles. The el cheapo chain store brands won't last near that long. Did you install AC Delco cap & rotor? Yes, it does make a difference. Did you put silicone dielectric grease on the terminals?

 

Being it ran and is just now acting up, I'd rule out the cap/rotor. You could always do it the old 'redneck' way, and pull a plug boot, stick another plug in the boot, and see if it sparks when you turn it over. Also, pulling out a plug (the easiest one to get to) will show you if it's wet with gas or not. If you have fuel and fire - you've got computer issues. Can you get a code reader on it?