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GMC Yukon won't start

I have a 1997 Yukon, 5.7 vortex V8 with 64,000 actual miles. It has always started immediately with very, very little cranking. Then it intermitantly and increasingly harder to start, until now it will not start at all. The engine turns over okay … but it just cranks away and never fires.

Confused.

When was the last time the spark plugs, fuel filter and plug wires changed? How old is the battery? have the battery and charging system been checked (Many auto part stores will check them for free.)

At 64,000 miles, it’s never had a tune-up. Original plugs, wires, etc. Battery is 2-3 years old, Charging system checked ok last year. As stated, the engine cranks, but never fires.

Try spraying a little starting fluid into the air intake while cranking the engine. If it fires up then quits, you have a fuel supply fault.

For spark, remove a plug, lay it against the block and turn the engine over, if no spark…

Long list for no spark.

Now I’m really baffeled …
I used the starting fluid and the Yukon started okay and kept running. Let it run for a couple of minutes, then turned it off. After a couple of minutes, I tried starting it again, but it did not fire. I gave it another shot of starting fluid and it fired up. Let it run for about 15 minutes to get it warm, and then shut it down, waited 5 minutes, and tried to start it again, it fired right off. Now, this morning, same thing … it will not fire. I’m guessing a sensor somewhere ???

The original spark plugs are now 12 years old. The gasket that seals the ceramic at the base of the plugs is likely deteriorated to the point that a little moisture will affect the plugs. It maybe a sensor, but changing out the spark plugs is way overdue. If this motor uses coils on top of the each plug then you don’t need new wires, but if it does use traditional spark plug wires they need to be changed too.

I believe new plugs and wires will give you the spark you need to fire up the cold motor without resorting to starting fluid.

The Coolant Temperature Sensor could be the problem. You could check the calibration of the CTS by measuring its resistance, noting the engine temperature, and checking to see if the value is within tolerance.

To save time and effort, the CTS could be changed. You have to make sure that the temp sensor you change is the CTS as the gauge or idiot light sensor is nearby.

Hope that is what it is.

What is the theory about a coolant temp sensor causing a complete no-start not even a fire? I certainly understand how a incorrect coolant temp sensor can keep a vehicle in open loop but it will still start.