How To Diagnose A No-Start Problem (3.1L V6 Buick, Oldsmobile)

STEP 2: Testing The Fuel Pump's Pressure

After eliminating the ignition system as the cause of the engine's no-start problem, the next step is to check the fuel pump.

If the fuel pump is faulty, it will not send any fuel to the engine. The end result is an engine no-start problem.

There are several ways to test the fuel pump, but the most accurate way is with a fuel pressure test gauge.

The fuel pressure gauge is connected to your vehicle's fuel system with a special adapter. This adapter is connected to the Schrader valve on the fuel injector rail.

You can find the fuel pressure specifications and the fuel pump pressure test explained in a step-by-step manner here: How To Test The Fuel Pump (3.1L V6 Buick, Oldsmobile).

The fuel system is NOT causing the no-start problem if:

• Fuel pressure is within the indicated 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 correctly conclude the fuel pump is not behind the engine's no-start problem.

The next step is to check for an anti-theft system problem. Go to: STEP 3: Anti-Theft System Checks.

The fuel system IS THE CAUSE of the no-start problem if:

• Fuel pressure is 0 PSI (or anything below the fuel pressure specification).

This confirms that the no-start problem is caused by a lack of fuel. This usually means that the fuel pump is bad and needs to be replaced.

STEP 3: Anti-Theft System Checks

The most common failure of the PASS-Key anti-theft system is the PCM (or BCM) not recognizing the key that you're using to crank and start the engine.

When this happens, you'll see one of two problems:

• The engine does not crank to start. The PCM has disabled the starter motor.
• The engine cranks but does not start. The PCM has disabled the fuel injectors after a few seconds of engine run time. In other words, the engine starts but runs for a few seconds and then shuts off.

Unfortunately, a PASS-Key failure (that is allowing the engine to crank but not start) can mimic a failed fuel pump problem and usually makes the vehicle owner think that the fuel pump has failed.

Is the PASS-Key system the one keeping your vehicle from starting? Here's how you can find out:

A PASS-Key system problem IS behind the no-start problem if the following three conditions are met:

• The fuel pump's pressure is within specification (as confirmed with a fuel pressure test gauge).
• All six spark plug wires are sparking (as confirmed with a dedicated spark tester).
• The engine starts with starting fluid (even though it'll stall after the starting fluid you sprayed into the throttle body gets consumed).

The PASS-Key systems leave specific trouble codes in the PCM or BCM's memory when a failure occurs in one of its components. Unfortunately, you usually need a professional-level scan tool to read these codes.

This doesn't mean you can't correctly pinpoint the PASS-Key system as the culprit behind your vehicle's no-start condition.

3.1L V6 Buick vehicles with PASS-KEY:

• 3.1L Buick Century: 1997-2005.
• 3.1L Buick Regal: 1994-1998.
• 3.1L Buick Skylark: 1996-1998.

3.1L V6 Oldsmobile vehicles with PASS-KEY:

• 3.1L Oldsmobile Achieva: 1996-1998.
• 3.1L Oldsmobile Cutlass: 1997-1999.
• 3.1L Oldsmobile Cutlass Supreme: 1994-1997.

STEP 4: Checking For A Blown Head Gasket

A blown head gasket will cause an engine no-start problem. The 3.1L V6 engine in your Buick (Oldsmobile) has two of them.

A blown head gasket can be confirmed with one of four tests. You can find all four tests explained in detail here:

• How To Test A Blown Head Gasket (3.1L V6 Buick, Oldsmobile).

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 engine compression test is probably one of the most overlooked tests when troubleshooting an engine no-start problem.

This test is almost always done after eliminating the ignition system and the fuel system as the sources of the engine's no-start problem.

I've written a tutorial that describes how to test the engine's compression and, more importantly, how to interpret its results. You can find it here:

• How To Test Engine Compression Test (3.1L V6 Buick, Oldsmobile).

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

The most important thing to remember when diagnosing an engine no-start problem, is that the engine needs 3 things to be able to start.

These 3 things are:

• Spark.
• Fuel.
• Air (compression).

When the engine does not start, it's because one of these is missing from the mix.

Therefore, testing an engine no-start problem literally boils down to a process of elimination.

Once you've confirmed that you've got spark at all cylinders, there isn't any need to spend time testing the ignition system. The next step is to make sure the fuel pump is working and so on and so on.

By checking these basic things (spark, fuel, air), you'll save yourself the frustration of replacing components that won't solve the problem.

More 3.1L V6 Buick, Oldsmobile Tutorials

You can find a complete list of 3.1L V6 Buick (Oldsmobile) tutorials in this index:

• GM 3.1L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test Engine Compression Test (3.1L V6 Buick, Oldsmobile).
• How To Test A Blown Head Gasket (3.1L V6 Buick, Oldsmobile).
• How To Test The Fuel Pump (3.1L V6 Buick, Oldsmobile).
• How To Test The 24X Crankshaft Position Sensor (1995-1997 3.1L V6 Oldsmobile Cutlass Supreme).