NO START 3: Checking Engine Mechanical Condition
One of the most overlooked areas, when testing a hard to diagnose cranks but does not start condition, is the mechanical condition of your 4.0L Jeep vehicle.
Checking the engine mechanical condition usually means doing an engine compression test and/or a blown head gasket test. These tests will confirm (or disprove) an internal engine problem is the root cause of the cranks but does not start condition your vehicle is experiencing.
Here are some specific tips:
- When performing an engine compression test, what you're looking for is an average compression reading of NO LESS THAN 120 PSI across all or the majority of the engine cylinders.
- If you have one or just two readings that are under 90 PSI your 4.0L Jeep vehicle will still start and run, albeit with a misfire condition.
- The following tutorial will help you do a compression test:
Cranks But Does Not Start Summary
By this point, in this tutorial, you now know that the cranks but does not start condition of your 4.0L Jeep is due to a lack of one of the following:
- Spark.
- Fuel.
- Air (from a lack of cylinder compression).
You now also know that you can perform specific tests to see what's missing from the mix (when you're cranking your Jeep to get it started). The tests I'm talking about are: spark test, fuel pressure test, and engine compression test.
Thankfully, all of these tests are done with simple tools. Which leads me to the next talking point.
To check the basics, you need tools. There's just no way around it. One of the analogies that I've always enjoyed repeating, about doing a job without the right tools is like trying to eat a bowl of soup with a fork.
So besides knowing what to test, you need tools to do those tests. You don't have to spend an arm and a leg, since you can buy a lot of diagnostics tools that are tailored for the pocket-books of the serious do-it-yourself-er. Here are some of the basic tools you'll need:
- A fuel pressure gauge.
- A spark tester.
- A compression gauge.
- A multimeter.
Most of these tools you can buy or rent for free (after you leave a cash deposit which you'll get back when you return the tool) at your local auto parts store (mainly AutoZone and O'Reilly Auto Parts). Or, if you want to save some bucks, you can buy them online.
More 4.0L Jeep Diagnostic Tutorials
You can find a complete list of tutorials here: Jeep 4.0L Index Of Articles. Below, is a sample of articles you'll find in this index of articles:
- How To Test TPS Codes: P0121, P0122, P0123 (1997-2001 Jeep 4.0L).
- How To Test The MAP Sensor (1997-2003 Jeep 4.0L).
- How To Test Engine Compression (Jeep 4.0L).
- How To Troubleshoot A Bad Fuel Injector (Jeep 4.0L).
- How To Test The Crankshaft Position Sensor (1994-1996 4.0L Jeep).
- How To Bench Test A Starter Motor (Step By Step) (at: easyautodiagnostics.com).
If this info saved the day, buy me a beer!
