Just installed a new timing chain set and resealed the intake, valve covers and plenum, as well as cleaned and resealed the injectors on my '96 Monte Carlo 3.1M V6. It started and ran fine for over an hour or more, but once I shut it down and tried to restart about an hour later, it began to backfire and crank hard, as if there were a hydrostatic lock in one cylinder. What can this be?
First thing I would do is make sure you have the plug wire's in correct location's. Other than that are you sure you had the timeing mark's rite when you installed the new chain?
I'd have to make sure battery has a full charge and battery connections good. Sometimes if vehicle is hard to start, people run the battery down? We can't do any testing if battery is down. Use a digital mutimeter across battery posts, everything off. The generic spec for a full charge is around 12.6 volts. Leave the meter leads touching the battery posts, have helper turn key to crank, the reading shouldn't drop below 9 volts, That reading may vary a little from one vehicle to another. Some say 9.6 volts, some say ten, you get the picture.
How long since a tune-up? Any applicable trouble codes? Does it backfire out the exhaust or intake? I'd want to check fuel trims, see if anything shows up? As far as hydrostatic lock, pull the spark plugs, see if any fluid comes out?
SOURCE: 1995 monte carlo starting and run problems
Sounds like the fuel is draining back towards the fuel tank, which is the reason for extended cranking till fuel reaches injectors. My guess would be the fuel pump in the fuel tank. It contains a REVERSE FLOW VALVE, which SHOULD prevent this. A visible way to check would to place a manual fuel pressure gauge on the fuel rail valve. After shutting the engine off note the degree of pressure drop, if any. Hope this helps
SOURCE: my car backfires and will not start.
check the fireing order of your plug wires u most likeley crossed a few wires and put them in the wrong order if u r looking at the front of the vehicle the front 3 cylenders are 2,4,6 starting from the front of the moter and the back 3 cylenders are 1,3,5 and the coil packs should be marked as to wich cylendr they go to if not the startin with the top coil pack the top plug wire pin is num1 and the second is num4 the next coil pack is 5 being the top pin and 2 being the bottem pin on the coil and the last coil pack is top pin cylender 3 and bottem is cylender 6. hope this helps
SOURCE: 2004 monte carlo, engine light on and engine
Not Good! Probably upper engine damage Intake or exhaust valve, possibly camshaft,Check the spark plug or wire condition.
SOURCE: my b 4000 4.0 litre misses while driving and
check the emission part of your truck for the backfire on deceleration
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