Ran fine, 15 mins later No Start. It Cranks, has Fuel Pressure and Spark.[SOLVED]

Hey Fellas,

I've got a '98 Suburban 5.7L that I just can't get to start. This is my spare vehicle that I drive occasionally on the weekends when I need a truck. The truck has been running and starting fine.

Here's what happened:
The other day, I drove the truck about 5 miles to the hardware store. This was the first time I had driven the truck in about a week. As usual, the truck started up and ran fine on the way to the store. However when I came out, the truck just would not start. It would crank and crank, but it would not fire. I had to have the vehicle towed home...

What I have Done and What is Known:
This happened about a week ago. Since then, I have done a little digging, and I have determined that I have good fuel pressure (via a gauge) and I hooked up a spark tester and I am getting spark. About two years ago, I upgraded the truck to MPFI using an OEM (Delphi) unit. The plugs and wires are fairly new as well. I only drive this truck maybe 6-10K miles a year, and it has ran and started fine right up until the full failure. I did notice a slight high idle on the way to the store, but it was negligible. So far, I went ahead and replaced the ignition control module, which did nothing. I also pulled the distributor cap and all appeared fine (it is only about a year old along with the plugs, wires, and MPFI unit). I also replaced the fuel pump about 2 years ago as well (only about 10K miles)

Possibilities:
since I'm getting spark, fuel and it's cranking, I'm a little stumped as to where to go next. AS stated, I just installed a new ignition control module, and the plugs wires, cap/rotor, MPFI and fuel pump have been replaced within 10K miles, and no running issues whatsoever were experience right up to the moment of failure.

Any input would be appreciated!

Have you checked for codes?

Shoot some starting fluid in the intake. That will narrow it down.

Yep, not showing any codes, at least not with my scanner (I don't have a tech II). Will try starting fluid tommorow. One thing I was reading about, could it be security system related? I read that the security has the pcm tell the fuel injectors to not fire,

Buick CIty said:

One thing I was reading about, could it be security system related? I read that the security has the pcm tell the fuel injectors to not fire,

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That is a possibility. I believe the Pssskey came out on these trucks in 98. Someone else will have to chime in who knows them better.

lamogo33 said:

Have you checked for codes?

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skylark said:

Shoot some starting fluid in the intake. That will narrow it down.

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lamogo33 said:

That is a possibility. I believe the Pssskey came out on these trucks in 98. Someone else will have to chime in who knows them better.

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It is not Security, the Security light goes off and the truck does not fire at all.

I scanned for codes and got nothing.

And, I tried starting fluid in the intake and again I did not get anything.

I'm thinking either my Distributor jumped time maybe due to a broken gear, or maybe the same thing with the timing chain. The chain could not have broken, because I am getting spark.

I am definitely no expert but I seem to remember something about distributer gear issues on Vortec engines.

SOLVED!

Scan tool showed the coolant temp sensor was reading -40 degrees! Apparently the engine does not allow itself to start when it thinks it is that cold. Disconnected the sensor, and it started right up. This also explains the final trip before it would not start where it was idling high. It must have failed enroute, and obviously the engine would idle high if it thought it was -40 degrees!

Have you replaced the sensor? Although that does look like the issue, I've learned that disconnecting one sensor can put the computer in limp mode, which is actually masking the issue from another sensor.

Example: Had a truck fail to start at a gas station, 300 miles from home. Was running rich the day before so I unplugged the ECT sensor and she fired right up. Made it home swapped in a new sensor plugged it in and problem came back. Was a HO2S that was reporting lean and tricking the computer to run rich. Just something to keep in mind.