TURNS OVER BUT WONT START

  • Tiny
  • bigglou
  • 1999 Chevrolet Tahoe
  • 110,050 miles

1999 chevy tahoe 5.7 v8, will turn over but will not start, replaced crank sencer, distributor cap, distributor rotor, ingnition moduler, ignition coil pack, spark plug, wires are good, relay swiches strater&fuel, and replaced the fuel pump, still the samething

Monday, March 12th, 2012 AT 11:31 PM

4 Answers

  • Tiny
  • Wrenchtech
  • Expert
  • 19,541 posts

All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.

Every engine requires spark, fuel and compression to run. That's what we have to look for.

These are the basics that need to be tested and will give us the info required to isolate a cause.

1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.

2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.

3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.

4) If all of these things check good, then you would need to do a complete compression test.

Once you have determined which of these functions has dropped out,
you will know which system is having the problem.

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Monday, March 12th, 2012 AT 11:48 PM
  • Tiny
  • fixitmr
  • Member

Cam sensor /hall effect/ pickup coil in distributor. Have to remove and disassemble.

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Monday, March 12th, 2012 AT 11:53 PM
  • Tiny
  • Wrenchtech
  • Expert
  • 19,541 posts

I wouldn't mess with anything in the distributor at this point until you get some idea what function is preventing it from starting. If you move that distributor you will need a professional scan tool to get it set right again

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Tuesday, March 13th, 2012 AT 12:04 AM
  • Tiny
  • tech911
  • Member

Basic diagnosing, late model vehicles give you the luxury of trouble codes. 98 and up C/Ks (Silverado, Tahoe, suburban) had a theft deterrent system that can cause this problem. Get trouble codes, or even better get a dealer to diagnose it for you. Beats guessing at parts. That way wastes time and money and worse yet you could CAUSE more problems than what you started with which again will cost more money and time for a PRO to diagnose.

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Tuesday, March 13th, 2012 AT 4:18 AM

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