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05-12-2021, 07:26 AM
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#1 |
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Registered User
Join Date: Aug 2012
Location: New Boston, New Hampshire
Posts: 34
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LS swap fires then quits
Swapped a 99 4.8 into my 72 c10. Got everything hooked up and ready to run. Starts immediately and then quitsafter a few seconds.. Computer was sent to Lt1swap.com to remove vats and what was not needed. In searching my issue it sounds like vats, how do I test for that or what else could be the problem? Thanks in advance.
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05-12-2021, 07:39 AM
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#2 |
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Post Whore
  
Join Date: May 2015
Location: Alabama
Posts: 14,673
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Re: LS swap fires then quits
Do you have the maf hooked up?
Any codes?
__________________
Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver |
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05-12-2021, 07:42 AM
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#3 |
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Senior Member
Join Date: Nov 2013
Location: East Tennessee
Posts: 2,200
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Re: LS swap fires then quits
does the fuel pump prime for a few seconds when you turn the key to "on" if so make sure it's also running when you get it started.
If so the VATS may not be disabled?
__________________
1967 C10 Step side 1968 C10 Step side 1970 Chevrolet K/5 Blazer 1972 Chevrolet K/5 Blazer ............. 
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05-12-2021, 07:53 AM
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#4 |
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Registered User
Join Date: Aug 2012
Location: New Boston, New Hampshire
Posts: 34
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Re: LS swap fires then quits
Maf is hooked up. Checked with a scanner and shows no codes. Pump has power with key on and cranking, can hear it when I turn key on.
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05-12-2021, 10:16 AM
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#5 |
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Registered User
Join Date: Nov 2014
Location: Austin
Posts: 749
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Re: LS swap fires then quits
Maybe check fuel pressure. You have enough gas in tank, right!
Maybe crank sensor...but usually that is a no start situation, not a run and stop scenario. Hope you get if figured out. Soon I will have my 2001 5.3L dropped in my '71...I am always nervous what is happening to you will happen to me. I too had LT1SWAP reprogram my ECM/PCM. EDIT: Per other thread...check for massive vacuum leak...such as leaving a port on the manifold wide open. Last edited by Davidf; 05-12-2021 at 10:38 AM. |
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05-12-2021, 10:44 AM
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#6 |
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Registered User
Join Date: Dec 2009
Location: Independence Mo
Posts: 4,119
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Re: LS swap fires then quits
Can you keep it running by feathering the throttle? I have had swaps that when you first hook up the battery after it has sat a while with it unhooked, that it won't stay running. It has to recalibrate where the IAC is, and once it's done that runs fine there after.
__________________
My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html |
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05-14-2021, 09:26 AM
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#7 |
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Registered User
Join Date: Aug 2012
Location: New Boston, New Hampshire
Posts: 34
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Re: LS swap fires then quits
Found my problem, forgot to plug hole in intake for egr tube, huge vacuum leak! Starts and runs now, just need to put exhaust and 02 sensors on.
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05-14-2021, 09:37 AM
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#8 | |
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Senior Member
Join Date: Nov 2013
Location: East Tennessee
Posts: 2,200
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Re: LS swap fires then quits
Quote:
that also shows how difficult it is to diagnose a problem without actually being there in person...an extra set of eyes is most always helpful....
__________________
1967 C10 Step side 1968 C10 Step side 1970 Chevrolet K/5 Blazer 1972 Chevrolet K/5 Blazer .............
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