You are here:

GMC Repair/crankshaft sensor

Advertisement


Question
I HAVE A 2003 Tahoe with less than 159k miles.  I went in the house took care of some person business.  Stayed about and hour or so. I  came back out and my truck wouldn't start
I had a Guy come out and check it. He put a gas towel over the throttle body and it cranked up for a minute.  He said the crank shaft sensor is gone. I know guessing can get very expensive.

Answer
Is the guy who helped you an experienced mechanic?  Usually if your truck won't start but it will fire for a little bit with a gas towel, it means it's a fuel problem.

Truck won't start.

Add fuel manually, with a towel.

Truck fires for a little bit.

It must be a fuel problem.  You know it's getting spark.

Most the time if your crank sensor goes out, the truck will show signs of life and will even run most of the time but roughly and badly.  If it just won't start at all but fires when you give it a sniff of fuel, then it's almost certainly a fuel pump.

Sit in the truck with the key off, fasten your seatbelt so it won't ding at you when you turn on the key, if you are in a noisy area, roll the windows up to make it quieter.  When it's totally quiet and the dingers will not ding, turn the key to the "on" position and listen carefully for the fuel pump to cycle.  You should hear it come on for between 1 and 3 seconds and then turn off.  The sound will be coming from behind you, inside the fuel tank.  If you didn't hear anything at all, then the fuel pump is not coming on.  Double check by raising the hood and removing the cap from the shrader valve in the fuel line.  After cycling the key switch once or twice, get a nail or something and push in on that shrader valve a little.  It should spray a very short burst of fuel at you if the fuel pump is working.  If you push that valve and you get a tiny dribble or nothing at all, then you have no fuel pressure and it's your fuel pump.  With that many miles the fuel pump should be getting ready to go anyway, so it's about that time.  People may tell you it's a plugged filter, but it was running fine when you drove it home, right?  Fuel filters don't suddenly plug themselves completely tight while the truck is sitting still.

On the other hand, the guy saying it's the crank sensor may be an experienced mechanic, and maybe he saw symptoms that you didn't describe.  Your question is short and contains very limited info, and that is what I'm basing my answer on.  I appreciate you choosing me, and I wish you the best of luck.  Please reply with all the detailed symptoms.  When it's cranking and not starting, is it showing signs of life, trying to kick over a little, or does it just crank dry?  Please, if you need to, feel free to give more detail and ask as much as you need.

GMC Repair

All Answers


Answers by Expert:


Ask Experts

Volunteer


The Man of Steel

Expertise

I will take a shot at anything. This service is free, it's worth a try. Please rate in terms of my willingness to help if I can.

Experience

Mechanic for 20+ years

Education/Credentials
AAS Degree in CAD, life experience

©2016 About.com. All rights reserved.