STEP 2: Testing The Fuel Pump's Pressure
Once you have confirmed that the ignition system is not the cause of the engine no-start problem on your 4.3L V6 Chevy S10 Pickup (GMC-S15 Pickup, GMC Sonoma), the next step of the diagnostic process is checking the fuel pump.
As you already know, the electric fuel pump in your pickup truck's tank is a critical component to the operation of the engine, as it's responsible for sending fuel from the fuel tank to the engine.
If the fuel pump is not working properly, it won't send fuel to the engine, resulting in the engine not starting or running properly.
To test the fuel pump and see if it's working properly, you can connect a fuel pressure gauge to the fuel filter with a special adapter.
This method of testing the fuel pump is one of the most accurate fuel pump testing methods to determine if the fuel pump is the cause of an engine no-start problem.
The following tutorials explain the fuel pump testing process in detail for the TBI and CPI equipped 4.3L engines:
- How To Test The Fuel Pump (1988-1995 4.3L TBI Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
- How To Test The Fuel Pump (1992-1995 4.3L CPI Chevrolet S10 Pickup, GMC Sonoma).
The fuel system is NOT causing the no-start problem if:
- Fuel pressure is within specification.
If the fuel pressure gauge registers the indicated fuel pressure specification, then you can confidently conclude that the fuel pump is working and delivering enough fuel to the fuel injectors.
You can also conclude that the fuel pump is not behind the engine's no-start problem.
The next step is to check for a blown head gasket. Go to: STEP 4: Checking For A Blown Head Gasket.
The fuel system IS THE CAUSE of the no-start problem if:
- Fuel pressure is 0 PSI (or anything below the fuel pressure specification).
The components that can cause a 0 PSI fuel pressure problem are:
- A bad fuel pump.
- A bad engine oil pressure switch.
- A bad fuel pump relay.
The components that can cause a low fuel pressure problem are:
- A bad fuel pump.
- A bad fuel pressure regulator.
STEP 4: Checking For A Blown Head Gasket
A head gasket is a gasket that sits between the cylinder head and the engine block and your 4.3L V6 pickup engine has two of them.
It plays a critical role in the proper functioning of the engine by sealing the combustion chamber, ensuring that coolant and oil don't mix with the combustion gases.
A failure in one or both head gaskets can cause various issues with the engine, including the engine not starting.
The most common reasons behind a blown head gasket leading to an engine not starting are hydro-lock and loss of compression between two side-by-side cylinders.
Hydro-lock occurs when coolant enters the combustion chamber and prevents the engine from turning over.
A head gasket failure between two side-by-side cylinders leads to a loss of compression in both of them, as compression from one cylinder leaks into the other, and vice versa.
Diagnosing a blown head gasket isn't difficult, and the following tutorial will guide you through the four tests you can perform:
A blown head gasket is NOT causing the no-start problem if:
- The engine oil has a normal color (in other words, it doesn't have a milky-white color).
- The coolant in the radiator remains undisturbed when cranking the engine (with the radiator open).
- The engine passed a block test.
Your next test is to check the engine's compression. Go to: STEP 5: Making Sure The Engine Has Good Compression.
A blown head gasket IS THE CAUSE of the no-start problem if:
- The engine oil has a milky-white color (like coffee with too much creamer).
- - or -
- The coolant in the radiator shot out when cranking the engine (with the radiator open).
- - or -
- The engine failed a block test.
STEP 5: Making Sure The Engine Has Good Compression
The process of engine compression in your 4.3L V6 Chevy S10 pickup (GMC S15 pickup, GMC Sonoma) plays a vital role in starting the internal combustion engine.
The compression process is initiated when the starter motor turns the crankshaft, causing the pistons to move upward, compressing the air/fuel mixture in the cylinders.
When the compression reaches a certain level, the spark plug generates a spark which ignites the compressed air/fuel mixture, starting the combustion process.
The resulting pressure created by the compressed air/fuel mixture pushes the pistons down, causing the crankshaft to turn, thus starting the engine.
It's important to note that checking the engine's compression is often overlooked when trying to troubleshoot an engine that won't start.
If you have already ruled out any issues with the ignition system, fuel pump, and head gaskets, using a compression tester to check the engine's compression is the next logical step in your diagnostic process.
The following tutorial explains how to perform an engine compression test and interpret the results:
- How To Test Engine Compression (1988-2003 4.3L V6 Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
An engine compression problem is NOT causing the no-start problem if:
- The compression of each cylinder is above 120 PSI.
An engine compression problem IS THE CAUSE of the no-start problem if:
- 2 or more cylinders have 0 PSI compression.
- - or -
- All cylinders have 0 PSI compression.
No-Start Troubleshooting Summary
Solving an engine no-start issue is a matter of methodically eliminating potential culprits until the root cause is identified.
To achieve this, it's necessary to test specific components and determine which of them is responsible for the lack of spark, fuel, or compression.
Fortunately, you can perform all the tests with relatively inexpensive tools that you can easily get from your local auto parts store or online retailers.
By taking a systematic approach to troubleshooting an engine no-start issue, you can save yourself the frustration and cost of replacing unnecessary parts.
More 4.3L Chevy S10 Pickup, GMC S15 Pickup, And GMC Sonoma Tutorials
You can find a complete list of 4.3L Chevy S10 pickup, GMC S15 pickup, And GMC Sonoma tutorials here:
Here's a sample of the tutorials you'll find in the index:
- How To Test The Fuel Pump (1996-2003 4.3L V6 Chevrolet S10 Pickup, GMC Sonoma).
- How To Test The EGR Valve (1988-1995 4.3L TBI Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
- How To Test For A Blown Head Gasket (1988-2003 4.3L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
- How To Test Engine Compression (1988-2003 4.3L V6 Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
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