C5 Intermitted starting issue
Thread Starter
7th Gear
Joined: Feb 2019
Posts: 7
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From: Northern California
C5 Intermitted starting issue
Howdy, ive got a 1999 base model, with an LS2 in it. I bought the car this way so im not 100% sure about the details of the swap, but ive read a bit about people that have done it before and they say it runs fine with the original ECU. Anyway, the car starts randomly, sometimes it fires right up first crank other times it will just crank and crank until you stop and try again. sometimes it back fires. Mostly i have to try to start it 3-6 times, turning the key all the way off and trying again. Once running it runs great, does not stall or anything.
Hoping someone has run into this problem before and it isnt related to the swap
Any input would be appreciated, Thanks
Hoping someone has run into this problem before and it isnt related to the swap
Any input would be appreciated, Thanks
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Le Mans Master
Joined: Feb 2012
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From: OK
Just because the engine cranks does NOT mean that the voltage is adequate to keep the C5 electronics happy. Measure the voltage across the battery posts. Needs to be greater than 12.5V. At 12.5 or less the engine may start but thr electronics are NOT going to be happy. Charge the battery fully. A good battery at full charge will measure 12.7 to 12.9 volts or more measured at the battery posts using a digital multimeter.
Pro
Joined: Jan 2003
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From: St. Johns Fl
Just because the engine cranks does NOT mean that the voltage is adequate to keep the C5 electronics happy. Measure the voltage across the battery posts. Needs to be greater than 12.5V. At 12.5 or less the engine may start but thr electronics are NOT going to be happy. Charge the battery fully. A good battery at full charge will measure 12.7 to 12.9 volts or more measured at the battery posts using a digital multimeter.
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Yes !!....the cars electronics are very fussy about voltage....ignition relay 42 takes a beating during a "cold start" of the engine...the C5 coil packs draw up to 10 amps each so we're talking almost 80 amps or so plus maybe 8 amps for the injectors !! ...during cranking you can do a voltage drop not just across the battery terminals but across the relay...you can hook the multi meters red lead to battery positive and the negative test lead to one of 2 test points on top of INJ 1 or INJ 2 fuses....crank the engine and read the voltage drop...should not be more than .2-.3 volts...you will also need to determine if you are getting spark AND injector pulse !!
Melting Slicks
Joined: Jul 2006
Posts: 2,332
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From: Silver Spring MD
Ignition Switch
Mine would crank but not start. After wasting 2 months diagnosing I replaced the Ignition Switch, Car started right up. Its a PITA to rip dash apart but it was necessary to fix my car.
Melting Slicks
Joined: Sep 2008
Posts: 3,117
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From: Espanola New Mexico
Since it was a swap, you might want to check ground connections to the engine, the one ground connection to the cylinder head might have not been made or maybe was left loose after the swap.
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Thread Starter
7th Gear
Joined: Feb 2019
Posts: 7
Likes: 0
From: Northern California
Just because the engine cranks does NOT mean that the voltage is adequate to keep the C5 electronics happy. Measure the voltage across the battery posts. Needs to be greater than 12.5V. At 12.5 or less the engine may start but thr electronics are NOT going to be happy. Charge the battery fully. A good battery at full charge will measure 12.7 to 12.9 volts or more measured at the battery posts using a digital multimeter.
Thread Starter
7th Gear
Joined: Feb 2019
Posts: 7
Likes: 0
From: Northern California
Would it start sometimes? Or not at all? Was it slowly going bad or just one day it gave up? If the new battery doesn't solve my issue that might be something im looking into.
Thread Starter
7th Gear
Joined: Feb 2019
Posts: 7
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From: Northern California
I will check them all tonight, i just rebuilt the TT and flipped the reverse gear, and while putting the new clutch in, i looked around the block from the bottom (was on a 4 post) and didnt see anything looking loose or missing, but this is my first LS.
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From: Cape Coral, Florida
As far as "people that have done it before with the original ECU"....It will not run fine but probably not at all if that "original" LS1 PCM is installed in an LS2 engine without some mods....the LS1 uses a 24X crankshaft reluctor wheel and an LS2 uses a 58 !!...your LS2 should have a 24X installed with the 99's PCM or some type of "ignition controller" if it has a 58X.
Last edited by C5 Diag; Feb 20, 2019 at 02:39 PM.
Thread Starter
7th Gear
Joined: Feb 2019
Posts: 7
Likes: 0
From: Northern California
As far as "people that have done it before with the original ECU"....It will not run fine but probably not at all if that "original" LS1 PCM is installed in an LS2 engine without some mods....the LS1 uses a 24X crankshaft reluctor wheel and an LS2 uses a 58 !!...your LS2 should have a 24X installed with the 99's PCM or some type of "ignition controller" if it has a 58X.
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Then you're golden !!....see if you have Tach movement (ignition pulse) when it cranks....see whether you are missing spark, fuel pressure/injector pulse or BOTH (crank sensor issue) !!
Thread Starter
7th Gear
Joined: Feb 2019
Posts: 7
Likes: 0
From: Northern California
Awesome thank you that’s good news, I will check that as well. have you heard of this combo before?
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
You have to check for spark and injector pulse like I had mentioned...to check injector pulse disconnect an injector...take a 12 volt test light (incandescent one) and connect it battery POSITIVE (control circuit is ground side switched)...the control wires are the striped wires on each injector....crank the engine and if the test light flickers you are getting injector pulse. I would want to check the feed wire on the injector too....the feed wires are pink...you would connect the test light to a good ground for this (key ON) !!...I'd probably want to check fuel pump pressure with a gauge also !!