Help! '99 Tahoe doesn't start...

[Osteoblast]

I have this '99 Tahoe an it doesn't start.
The previous owner guessed it's the passlock.


-Security light not on or flashing
-new spark plugs
-new spark plug wires
-new distributor
-spark plugs getting power and firing
-fuel pressure 50 psi

-tech2 shows P0463

Engine cranks but won't fire up

What should I check or do next?

Thanks!

 

[Osteoblast]

It's a 5.7 vortec

 

[Jeff Janssen]

It's a 5.7 vortec

Fuel pressure may be too low. See if it tries to start with a little (just a little) shot of quick start.

 

[618 Syndicate]

If it will not start at all, it's unlikely to be the passlock. Especially without a flashing security light.
Crank, start, almost immediately die is the passlock symptom.

 

[Osteoblast]

Fuel pressure may be too low. See if it tries to start with a little (just a little) shot of quick start.

Unfortunately not.

 

[stutaeng]

I'm assuming you already checked for spark? Fuel pressure does seem low. Try to prime it a few times to see if can get pressure to increase more, then try cranking it again to see if it fires. My Vortec engines of this vintage start at 55 psi of pressure, but I think spec is 60-62 psi...

You just bought this truck?

 

[Osteoblast]

Just bought it. Used but in awesome condition with the known starting issue.
Spark, yes.

 

[bigshane]

I've been plagued similarly (two diff. gmt400 '99s) and solved it by fully charging or replacing the battery and fixing blown-out corroded connections in the crappy lead-disc-spacer arrangement between the two positive batt cables / terminal connection. Though it would spin the starter decently, and had enough juice to get fuel pressure readings, and I could pull obdii codes, for some reason they must have been undervoltage when cranking. (or I lucked out twice )

 

[Osteoblast]

I replaced the battery with a brand new one.

 

[Schurkey]

You need:

1. A burnable air/fuel mixture
2. Adequate compression. GM spec at one time was 100+ psi cranking pressure.
3. A spark ACROSS THE PLUG GAP, AT THE RIGHT TIME.
4. Adequately non-restrictive exhaust. When the exhaust is restricted, the engine will often pop or run for a short time, then stall. The exhaust is unlikely to be so plugged that the engine won't even pop.

Lots of folks mistake "spark on my spark tester" for "spark across the plug gap". If the plugs are fouled, there's spark...but not across the gap.

What does the scan tool show for Cam Offset when cranking? It's REAL easy to get the distributor stabbed-in a little off. Any other sensor data looking goofy? Engine coolant temp same as ambient temp when the engine hasn't run for a long time? MAP sensor showing ambient pressure when the key is on but the engine isn't running?

EGR valve isn't stuck open?

What is your cranking vacuum?

Is the gasoline so old it won't burn? Gas tank empty, but the gauge shows it has fuel?

As said, fuel pressure seems suspicious. How old is the fuel filter?