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1996 Chevy Z-71 P0337 Fault: No Start, Black Spark Plugs, Fuel Pressure Issues

Model: 1996 Chevy Z-71 Fault Code: P0337 Posted: 2006-07-11 06:02

My 1996 Chevy Z-71 will turn over all day but won't start. Spark plugs are black, indicating excessive fuel delivery. I checked the crankshaft position sensor and measured only 2.5 volts on the yellow wire during cranking—should be 5 volts according to the service manual. After replacing the sensor (Wells brand, mounted behind the balancer with an 8mm bolt), the truck still won't start. The brown wire shows 12 volts when the key is on. I've confirmed no fire issues; the engine turns over but backfires when the key is released. Occasionally, it seems to respond briefly after returning the key to 'ON' before backfiring again. I haven't touched the distributor since last year's tune-up. I suspect a timing issue or fuel system problem. I plan to check the timing soon and will also inspect for potential issues like a worn timing chain or sludge in the oil, especially given the high mileage. The P0337 code suggests a crankshaft position sensor fault, but since replacing it didn't resolve the issue, I believe there may be an underlying fuel delivery problem. A fuel pressure gauge reading shows 62 psi when primed, dropping to 58 psi after two minutes and falling completely to zero when the key is turned off. All spark plugs are wet with fuel, and gas is visibly present on the intake manifold. I suspect a faulty fuel pressure regulator or fuel meter body—though the latter may require replacement due to cost and previous troubleshooting efforts. The dealer provided a V-6 compatible part instead of the correct V-8 version for my truck. I will exchange it tomorrow and update once the engine starts.

Related fault codes

P0337

Comments (6)

Anonymous 2006-07-11 08:26

You still have no spark? Could there be an air gap issue with the crankshaft position sensor? This might explain why the P0337 code persists even after replacement.

Anonymous 2006-07-11 09:30

The engine turns over but backfires when the key is released. It occasionally seems to start briefly after returning to 'ON' before backfiring—this could indicate a timing misalignment or fuel delivery issue, possibly related to ignition timing or fuel pressure.

Anonymous 2006-07-11 13:21

Has the distributor been adjusted recently? What brand of crankshaft sensor did you install? Where is it mounted—behind the balancer? Are there any adjustment slots on the mounting hole?

Anonymous 2006-07-11 15:35

I mounted the sensor behind the balancer using one 8mm bolt. It's a Wells brand, purchased at AutoZone—the only one available that day. I haven't checked timing yet but plan to do so this afternoon. The distributor hasn't been touched since last year when it was replaced during a full tune-up.

Anonymous 2006-07-11 16:29

Does the balancer need removal to access the sensor? Is there any visible damage to it? Some GM engines had known crankshaft sensor defects from factory, which may require a scan tool to relearn cam and crank positions. Check if the mounting hole allows adjustment. Timing chains can also fail at high mileage with sludgey oil—try loosening the distributor slightly and turning it manually to realign timing. A scanner is often necessary for codes like P0337 to confirm proper cam and crank synchronization. Hope this helps! Good luck, and please keep us updated. — Jeff

Anonymous 2006-07-12 18:58

I think I found the root cause—the original crank sensor was faulty. After replacement, the P0337 code cleared. Today, I tested fuel pressure: 62 psi when primed, dropping to 58 psi after two minutes and falling to zero when the key is turned off. All spark plugs are wet with fuel, and gas is visible on the intake manifold. I’m 90% confident it’s a failing fuel pressure regulator or fuel meter body. Since I’ve already spent significant time troubleshooting, I’m opting for replacement of both components—though the dealer mistakenly provided a V-6 part instead of the correct V-8 version. I’ll exchange it tomorrow and post confirmation once the engine starts. Thanks to Jeff for the helpful advice!