Hey all, I have a 99 qx4 with the 3.3 I recently changed the heads an all new sensors, even put a new distributor, every thing has power an ground when I check with a test light but will not fire when cranking, any help would be awesome
Hello,
It sounds like you've done some significant work on your 1999 Infiniti QX4's 3.3L engine, and it's frustrating to have it not start after all that effort. A "no-fire" condition after a major engine repair like a head gasket job often comes down to one of a few critical things.
Since you've confirmed you have power and ground to your new sensors and distributor, let's think about the "why" behind the lack of spark or fuel. The fact that it cranks but doesn't fire points to a breakdown in the air, fuel, or spark triangle—or, more specifically, the timing of those elements.
Here's a breakdown of the most likely culprits and what to check, in order of probability:
1. Camshaft and Crankshaft Timing
This is the single most common cause of a no-start condition after a head gasket or timing component job. Even if the timing marks look correct, it's easy to be off by a tooth, and that's all it takes for the engine not to fire.
Action: Double-check your timing. Remove the timing belt cover and ensure the crankshaft and camshaft sprockets are aligned perfectly with their timing marks. Pay close attention to the camshaft sprockets—a common mistake is to have one of them off by a tooth. On the VG33E engine, the timing marks are very specific, so consult your service manual or a reliable diagram to be certain.
2. Distributor Position
You mentioned a new distributor, which is another area for potential error. The distributor's position directly controls the spark timing.
Action: Verify the distributor is "dropped in" correctly. The distributor gear must mesh with the camshaft gear in the correct orientation. If it's off, it will be sending a spark to the wrong cylinder at the wrong time. The rotor inside the distributor should point to the correct position for cylinder #1 when the engine is at top dead center (TDC) on its compression stroke.
3. Firing Order and Spark Plug Wires
With a new distributor and a head job, it's easy to mix up the spark plug wires. An incorrect firing order will prevent the engine from running.
Action: Re-verify your firing order. For the 3.3L VG33E engine, the firing order is 1-2-3-4-5-6. The cylinders are numbered from front to back, with the passenger side being 1, 3, 5 and the driver side being 2, 4, 6. Make sure the spark plug wires are routed from the correct post on the distributor cap to the corresponding spark plug.
4. Fuel and Spark Confirmation
While you've checked for power and ground, you need to confirm you're actually getting spark and fuel.
Spark Check: Pull a spark plug and re-connect it to its wire. Have someone crank the engine while you hold the plug against a grounded metal part of the engine block. You should see a strong, blue spark. Use insulated pliers for safety! If there's no spark, you could have a faulty crank or cam position sensor (even if it's new) or an issue with the ignition control module.
Fuel Check: Listen for the fuel pump to prime when you turn the key to the "on" position. You should hear a distinct whirring sound from the rear of the vehicle. You can also press the Schrader valve on the fuel rail while an old rag is over it (to catch gas) to see if you have pressure. Be cautious of fuel spray!
Given that you've already verified power and ground to your components, the most probable cause is a mechanical or timing issue related to the work you just completed. Start by triple-checking your timing belt and distributor alignment. It's tedious, but it's the most likely solution. Good luck!
