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Old September 25th, 2013, 10:56 AM   #1
Carbon
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Default 98 Silverado issue

My brother has a 98 Chevy silverado with a 5.7 vortec in it. It will start and run but shut off after a few minutes and not start back up. Let it sit for a bit and it will start. 30 seconds later it will shut off. When it dies it looses spark. He has changed the distributor, coil, ignition module and crank sensor with no solution. Any ideas?
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Old September 25th, 2013, 09:31 PM   #2
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Do you have a scan tool? Need to see if there is RPM on the scanner when it won't start. Could be an ign. switch isssue, Check the voltage on the ECM-1 fuse when it won't start.

if you lose communication with the vcm when it won't start thats a dead giveaway it is losing power or something is shorting out shutting the vcm down.
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Old September 26th, 2013, 08:09 AM   #3
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Thank you. What will the RPMs tell me when I have my scanner hooked up when it wont start? Will the ECM-1 voltage be low or 0?
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Old September 26th, 2013, 08:22 AM   #4
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If you don't have RPM w/cranking you need to look at the crank sensor ckt, if you do have RPM whne cranking then it is not a crank sensor issue, it could be a module or wiring issue to the module/coil.

the ECM-1 fuse should be near 12v, if the ign. switch is bad it might be 0- 7 or 8 volts. volts.
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Old September 26th, 2013, 08:33 AM   #5
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We will do some looking. Thank you.
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Old September 27th, 2013, 02:13 PM   #6
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No RPM reading when turning the truck over. What does this mean?
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Old September 27th, 2013, 04:13 PM   #7
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I believe it gets its rpm signal from the crank sensor.. did u get a gm sensor or no? we have seen issues with non oem crank sensor not reading correctly, its either that or wiring. have seen the crank sensor wiring rubbed through along timing cover area.. good luck
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Old September 27th, 2013, 07:29 PM   #8
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He replaced the crank sensor a year ago with an advanced auto parts one which was aftermarket I'm sure and not gm.
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Old September 27th, 2013, 07:38 PM   #9
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check the ground at the front of the block, by the crank pulley. also check the ground on the fender behind the battery.
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Old September 27th, 2013, 08:15 PM   #10
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Quote:
Originally Posted by davidkassie View Post
I believe it gets its rpm signal from the crank sensor.. did u get a gm sensor or no? we have seen issues with non oem crank sensor not reading correctly, its either that or wiring. have seen the crank sensor wiring rubbed through along timing cover area.. good luck
X2

I would suspect a bad crank sensor or the wiring going to it.
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Old September 28th, 2013, 11:24 AM   #11
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BTW what is frdboy doing in Chevy Tech? I assume frd = ford. Hahaha
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Old September 28th, 2013, 11:25 AM   #12
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Quote:
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BTW what is frdboy doing in Chevy Tech? I assume frd = ford. Hahaha
Looks like he's trying to help you fix your broke truck.
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Old September 29th, 2013, 08:01 AM   #13
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Quote:
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Looks like he's trying to help you fix your broke truck.
It's much appreciated. Was just goofing.
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