Intake manifold fills up with gas have changed the fuel pump air intake sensor fuel filter and pcm

If your 1991 Chevy's 4.3 Vortec engine has spark and fuel, but still fails to ignite, there are several possible reasons to consider. Timing: Make sure the burn time is set correctly. Incorrect timing can prevent the engine from starting. Double-check the timing marks to make sure they align properly. Compression: Make sure the engine has adequate compression. If the pressure is low in one or more cylinders, starting problems may occur. A compression test will help determine this. Fuel Delivery: Even though you said it has gas, pay close attention to the fuel delivery system. Make sure the fuel pump is working properly, the fuel filter is clean, and the fuel lines are not clogged or leaking. Air intake: Inspect air intake for blockages or leaks. A clogged air filter or leaking intake manifold gasket can affect engine performance. Vacuum leaks: Check the vacuum lines and connections for leaks. A vacuum leak can cause an uneven mixture of air and fuel and cause starting problems. Sensors: The engine relies on sensors to send information to the computer unit (ECU). Defective sensors such as the crankshaft position sensor or camshaft position sensor can prevent the engine from stalling. Wiring and connections: Ensure all electrical connections are secure and non-corrosive. Damaged wiring or loose connections can block signals to engine parts. ECU/PCM: The engine's computer (ECU/PCM) can be faulty, preventing proper signals from reaching the engine components. Distributor cap and rotor: If your engine uses a distributor, inspect the distributor cap and rotor for any signs of wear or damage.

Hi,
Here is the location of the "Knock Sensor" you requested, I hope it helps you. It is Number 17. for future reference here is the list of the others
1 = Camshaft position sensor (CMP)
2 = Crankshaft position sensor (CKP)
3 = Engine Control relay (EC) -engine bay fusebox/relay plate 1
4 = Engine Coolant temperature sensor (ECT)
5 = Exhaust gas recirculation valve actuator (EGR)
6 = Fuel Filter
7 = Fuel Filter Heater - in fuel filter housing
8 = Fuel Flow control valve - on high pressure fuel pump
9 = Fuel Rail pressure sensor(FRP)
10 = Fuel Temperature sensor - on high pressure fuel pump
11 = Glow Plugs
12 = Glow Plug Relay 1 - engine bay fuse box/relay plate 2
13 = Glow Plug relay 2 - engine bay fuse box/relay plate 2
14 = High Pressure fuel pump
15 = Injectors
16 = Intake air temperature sensor (IAT) - in MAF sensor
17 = Knock Sensor (KS)
18 = Mass Air Flow sensor (MAF)

I would first start with the coil, distributor cap, rotor, spark plugs, and the spark plug wires. If that doesn't fix the problem, I would then change the fuel pump (located in the gas tank) and the fuel pump relay switch (located in the kick panel on the driver's side). If that still does not fix the problem, I would change out the Air Flow Sensor (located on top of the air filter box), and the Fuel Sensor (located where the air filter tube attaches to the intake manifold).

sounds like a coil problem to me

What year vehicle ? mass air flow or speed density fuel control . Do you have a scan tool that can view sensor data . What are the fuel trims ( short & long term ) showing ? PCM problem ? O2 sensors stuck lean , adding propane , do the O2 sensors go rich ?

2.6L Engine

1. Before servicing the vehicle, refer to the precautions in the beginning of this section.
2. Drain the cooling system.
3. Relieve the fuel system pressure.
4. Remove or disconnect the following:
   • Negative battery cable
   • Hood
   • Accessory drive belts
   • Accelerator cable
   • Positive Crankcase Ventilation (PCV) valve and hose
   • Air intake duct
   • Fuel pressure regulator vacuum line
   • Canister hose
   • Brake booster vacuum line
   • Engine wiring harness connectors at right wheel housing
   • Ground cable connector at the intake manifold, starter and firewall
   • Heated Oxygen (HO2S) sensor connector
   • Alternator wiring connectors
   • Oil pressure switch connector
   • Starter motor harness connectors
   • Ignition coil connector
   • Spark plug wires
   • Distributor
   • Exhaust front pipe
   • Exhaust Gas Recirculation (EGR) gas temperature sensor connector
   • Air pump
   • EGR pipe
   • Heat shield
   • Exhaust manifold
   • Throttle Position (TP) switch connector
   • Cooling fan
   • Water pump pulley
   • Power steering pump
   • Intake manifold
   • Crankshaft pulley
   • Front cover
   • Timing belt. Refer to the Timing Belt unit repair section.
   • Valve cover
   • Rocker arms
   • Camshaft
   • Cylinder head

Cylinder head bolt loosening sequence - 2.6L engine

1. To install:
2. NOTE: Refer to Section 1 of this manual for the cylinder head torque sequence illustration. The illustration is located after the Torque Specification Chart.
3. NOTE: Lubricate the cylinder head bolts with clean engine oil for assembly.
4. Install the cylinder head with a new gasket. Tighten the bolts in sequence as follows:
5. Step 1: 58 ft. lbs. (75 Nm)
6. Step 2: 72 ft. lbs. (98 Nm)

1. Install or connect the following:
2. Camshaft

• Rocker arms
• Valve cover
• Timing belt
• Front cover
• Crankshaft pulley. Tighten the bolt to 87 ft. lbs. (128 Nm).
• Intake manifold
• Power steering pump
• Water pump pulley
• Cooling fan
• TP switch connector
• Exhaust manifold
• Heat shield
• EGR pipe
• Air pump
• EGR gas temperature sensor connector
• Exhaust front pipe
• Distributor
• Spark plug wires
• Ignition coil connector
• Starter motor harness connectors
• Oil pressure switch connector
• Alternator wiring connectors
• HO2S sensor connector
• Ground cable connector at the intake manifold, starter and firewall
• Engine wiring harness connectors at right wheel housing
• Brake booster vacuum line
• Canister hose
• Fuel pressure regulator vacuum line
• Air intake duct
• PCV valve and hose
• Accelerator cable
• Accessory drive belts
• Hood
• Negative battery cable

1. Fill the cooling system.
2. Start the engine and check for leaks.

The two-wire Intake Manifold Air Temperature (IAT) sensor is installed in the intake manifold with the sensor element extending into the air stream:

1. This is a Negative Thermal Coefficient (NTC), meaning that as the manifold air temperature increases, the resistance (voltage) in the sensor decreases, and vice-versa.
2. The IAT sensor provides an input voltage to the PCM, indicating the density of the air entering the intake manifold based on intake manifold air temperature. When the ignition is turned ON , a 5-volt power circuit is supplied to the sensor from the PCM. The sensor is grounded at the PCM through a low-noise, sensor-return circuit.
3. The PCM uses this input to determine:
   Injector pulse-width (air: fuel ratio) Ignition timing (to prevent spark knock)

Fig. IAT sensor installed in the intake manifold of a 5.2L engine. Others similar

replace the fuel filter,if this does not help,replace the fuel pump.

use intake manifold cleaner to resistors in mas air flow sensor(will have to remove from air intake hose and take front screen off first)HAS THREE SMALL RESISTORS DONT DAMAGE THEM

What year is it?
4 cyc or V6?
====
I will assume you has a fresh tank of gas.
Here's a lot of to do / to check list.

clean air filter
clear air passage intake tube
clean mass air sensor MAS with electronic part cleaner
clean carb. or throttle body with carb. cleaner.
check or replace spark plug/wires/cap/rotor
check timing
change coolant (it's over due)
oil change (it's over due)
fuel filter (it's over due)

Give it a little TLC and it me know