Quite a few engine management components are involved in getting the engine started in your V8 Chevy Express (GMC Savana) van. If any one of them fail or experience issues, the engine isn't gonna start.
In this guide, I'm gonna focus on two specific components (fuel pump and CKP sensor) and internal mechanical engine problems (specifically, a blown head gasket and a blown engine) as the culprits of the engine no-start issue in your van.
Although diagnosing an engine no-start issue can be a bit of a head-scratcher to diagnose and fix, I can tell you that there is a method to the madness. In this guide, I'll explain a specific testing strategy that'll help you find the source of the engine no-start so that you can resolve it without wasting time and money.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Diagnosticar Un Arranca Pero No Prende (2003-2013 Chevrolet Express, GMC Savana) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the gasoline powered 4.8L, 5.3L, and 6.0L V8 engines only:
- Chevrolet Express 1500, 2500, 3500: 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013.
- GMC Savana 1500, 2500, 3500: 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013.
Difference Between A No-Start And A No-Crank
One of the things that's gonna help you troubleshoot the problem on your Express (Savana) van is to know that an engine no-crank and no-start problem are two different issues. I'll explain:
No-Start Condition: When your van has an engine no-start issue, it means that when you try to start the engine, you hear (and feel) the starter motor turning the engine over, but the engine itself doesn't actually start running.
This can happen because the engine isn't getting:
- Spark (the electric spark needed to ignite the fuel).
- Fuel (gasoline).
- Engine compression.
So to summarize, your van's engine is trying to start, but a lack of air, fuel, or compression is preventing it from doing so.
No-Crank Condition: Now, an engine no-crank condition is a bit different. When your van is experiencing a no-crank condition, it means that when you turn the key to start the engine, nothing happens at all. The starter motor doesn't turn the engine over.
This usually occurs because of a problem with one of the following components:
- The battery.
- The starter motor.
In short, with a no-crank condition, the engine isn't even attempting to start because it's not moving.
If you're van is experiencing a no-crank condition, you need to start by checking the battery (it might be fully discharged) and then testing the starter motor.
The Most Common Components That Cause An Engine No-Start
It's been my experience that the most common components behind an engine no-start are:
- Bad Fuel Pump: The engine in your van needs fuel to start and if the fuel pump isn't working properly, it can't deliver the gasoline the engine needs, and it won't start.
- Bad Crankshaft Position (CKP) Sensor: The CKP sensor plays a crucial role in the engine's ignition system by providing real-time data about the crankshaft's position and speed (as the engine cranks and runs), allowing the ECM to precisely control the timing of fuel injection and ignition spark. If the CKP sensor has failed, the engine won't start due to a lack of fuel injection and spark.
- Blown Head Gasket: Think of the head gasket as a seal that keeps everything in the engine where it should be. If it blows, stuff can leak out or mix where it shouldn't, causing big problems for your engine and making it hard to start or not start at all.
- Engine Compression Issues: Inside your engine, there are these moving parts that help it do its job. If something goes wrong with them, like if they're not compressing the air/fuel mixture right, your engine might not have the power it needs to start.
Now, while there are numerous potential reasons why an engine won't start, issues with the fuel pump, crankshaft position (CKP) sensor, and internal mechanical engine problems are indeed among the most common culprits encountered by mechanics and technicians.
Basic No-Start Problem Diagnostic Tests
The engine needs three core things to start:
- Air (compression): Without sufficient compression, the air-fuel mixture won't ignite effectively, leading to a no-start condition.
- Fuel: If there's a lack of fuel due to a fuel system malfunction, the engine won't start
- Spark: Without spark from the ignition system, combustion won't happen, resulting in a no-start condition.
Understanding that the engine is not gonna start if any of these three things is missing or compromised (while the engine is cranking) is the key to effectively diagnosing an engine no-start issue.
By systematically checking for spark, fuel delivery, and engine compression during the diagnostic process, you can narrow down the potential causes of the problem and work towards a solution that's gonna solve it.
Over the years, I've developed a specific order of tests I perform when diagnosing an engine no-start issue to see which one of these (air, fuel, or spark) is missing.
This set of diagnostic tests has helped me to quickly narrow down the issue to a few specific components (that I can further test to see if they're bad or good):
- Check For Diagnostic Trouble Codes (DTCs).
- Spark Test.
- Fuel Pressure Test.
- Head Gasket Check.
- Compression Test.
Each of the five tests above serve a specific purpose in the overall engine no-start diagnostic, here are the details:
STEP 1 - Check For Diagnostic Trouble Codes (DTCs): Diagnostic trouble codes (DTCs) stored in the vehicle's engine control module (ECM) can provide valuable clues about the underlying cause of the engine's no-start problem.
These codes are generated when the PCM detects abnormalities in various engine systems, such as the ignition or fuel delivery systems. By retrieving and analyzing these codes first, I can quickly narrow down the list of potential issues and focus my diagnostic efforts more effectively.
Unfortunately, not all engine no-start issues will trigger the PCM to set a diagnostic trouble code (helping pin-point the exact cause of the problem). This can frustrating, but while disappointing, it's not the end of the world.
If I do find DTCs stored in the PCM's memory, I thoroughly research them to see if they are related to the immediate no-start problem or are related to engine performance issues (when the engine is running).
STEP 2 - Spark Test: Serves to check if all 8 cylinders are getting the spark they need. Without spark, the gasoline the injectors are injecting into the cylinders won't ignite, and the engine won't start.
The most common cause of a no-spark issue causing the engine to not start is a bad CKP sensor. When it fails, none of the 8 ignition coils will produce and deliver spark to the spark plugs.
So, if after testing the ignition coils and they're producing and delivering spark to their spark plugs, you can conclude that the CKP sensor is OK. Further, you've eliminated the ignition system as the cause of the engine no-start issue and can move on to the next step -testing the fuel pump.
If after testing all 8 ignition coil high tension wires for spark and none of them sparked. You can generally conclude that the CKP sensor has failed. The cool thing is that it can be tested to see if has failed.
You can find the CKP sensor test here:
STEP 3 - Fuel Pressure Test: This one's like checking the van's blood pressure. The objective is to see if the fuel pump is pumping enough gas to the engine. If not, it might be the culprit of the no-start issue.
The most accurate way of diagnosing the condition of the fuel pump (to see if it has failed) is to measure it's fuel pressure output with a fuel pressure tester.
The cool thing is that you can buy a quality fuel pressure tester and it won't cost an arm and a leg.
You can find the fuel pump pressure test here:
- How To Test The Fuel Pump (2003-2007 V8 Chevrolet Express, GMC Savana).
- How To Test For The Fuel Pump (2008-2013 V8 Chevy Express, GMC Savana).
STEP 4 - Head Gasket Check: This test is like a doctor checking for a fever. You want to see if there are any signs that the head gasket is blown and causing trouble in the engine.
There are three common ways of testing for a blown head gasket, two of those three require no tools:
- Checking for Oil-Coolant Mixing: This test involves simply pulling out the engine oil dipstick and checking to see if the engine oil sticking to it is mixed with coolant. If it is, the engine oil will have the color of 'coffee with too much creamer'.
- Compression/Combustion Pressure Escaping Thru Radiator: This test is done by removing the radiator cap from the radiator and then cranking the engine. If the coolant is forcefully expelled (as the engine cranks), you've got a blown head gasket on your hands.
- Using a Block Tester (Combustion Leak Tester): The block tester typically consists of a test fluid and a hand pump or bulb. You start by removing a small amount of coolant from the radiator or coolant reservoir and adding the test fluid to the tester. Then, you insert the tester into the opening where the coolant was removed and use the hand pump or bulb to draw air from the cooling system through the test fluid. If the test fluid changes color (usually from blue to yellow) during this process, it indicates the presence of combustion gases and suggests a blown head gasket.
You can find the four head gasket tests explained in detail here:
STEP 5 - Compression Test: I reserve this test for last since it's the most labor intensive of the previous four tests.
Specifically, the engine compression test helps evaluate the engine's ability to compress air within its cylinders, which is crucial for generating the pressure necessary for combustion and starting the engine.
You can find the engine compression test explained in detail here:
What Tools Do I Need To Diagnose An Engine No-Start Issue
To be able to perform the tests I've outlined in this guide, you'll need some basic diagnostic and hand tools. These tools can be purchased online for relatively affordable prices. Here's the list:
- A Generic Scan Tool: This tool allows you to retrieve diagnostic trouble codes (DTCs) from the vehicle's onboard computer (PCM) and offers basic live data streaming capabilities, allowing you to monitor engine parameters in real-time.
- A Spark Tester: A spark tester allows you to safely and accurately check for the presence of spark at the spark plug wires during cranking.
- Fuel Pressure Gauge: This tool enables you to safely and accurately measure the fuel pressure in the fuel system. The Chevy Express (GMC Savana) vans come equipped with a fuel pressure test port that makes testing the fuel pressure a breeze.
- A Compression Gauge: A compression gauge allows you to measure the compression pressure in each cylinder of the engine.
- Basic Hand Tools: Having a set of basic hand tools (socket and ratchet set, wrench set, screwdriver set, multimeter, etc.) on hand will greatly facilitate your ability to diagnose and repair the engine no-start problem.
Most if not all of these tools can be purchased online for relatively cheap prices, but it's important that you avoid cheap knock-off tools. Buying a known automotive tool brand will ensure a quality tool that'll give you an accurate and reliable result and that'll last more than one use.
It's All A Process Of Elimination
The most important thing to remember, when diagnosing (and resolving) your van's engine no-start issue is the importance of compression (air), fuel, and spark in the engine starting process. This knowledge will provide you a framework for your troubleshooting efforts, helping you focus on the essential components and systems that need to be checked and tested.
By systematically testing and eliminating potential ignition and fuel system components and internal engine issues that when they fail can cause a no-start condition, you can effectively diagnose the problem and take appropriate corrective action to get the engine running again.
While diagnosing an engine no-start problem may require patience and persistence (not to mention buying some tool you many not currently have in your tool box), taking a methodical diagnostic approach is essential for ensuring you find the exact cause of the issue and avoid wasting time and money (replacing components that don't solve the issue).
More Chevy Express/GMC Savana Articles And Tutorials
You can find a complete list of articles and diagnostic tutorials for the V8 Chevy Express and GMC Savana here:
Here's a sample of the tutorials you'll find in the index:
- How To Test For The Fuel Pump (2008-2013 V8 Chevy Express, GMC Savana).
- How To Test The CKP Sensor (2008-2013 Chevrolet Express, GMC Savana).
- How To Diagnose An Engine Cranks But Does Not Start Problem (2003-2007 V8 Chevy Express, GMC Savana).
- How Can I Tell If The Automatic Transmission Is Bad? (2003-2013 Chevrolet Express, GMC Savana).
If this info saved the day, buy me a beer!
