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Old 03-16-2017, 09:05 PM   #1
LA_85
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5.3l swap popping

I recently i swapped my old 350 for a 5.3l LS. Took me months to do this. A few weekends ago it was time to turn the key to see what i had. And when i finally got the nerve to do so, my motor just pops back through the intake. I put my scanner on it and it gave me a code for "crankshaft sensor". Replaced it and still did the same thing. Can anyone out the there tell me what the problem is?
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Old 03-17-2017, 06:27 AM   #2
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Re: 5.3l swap popping

Welcome to the site. I've never done an LS swap and not real big on computer controlled servicing, but it sounds like one component isn't talking to the other. Something is either not connected properly, wiring issue, other bad component. There is an LS swap message board where I'm sure you'll find your best answers.

What did you do with that Olds 350?
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Old 03-17-2017, 06:40 AM   #3
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Re: 5.3l swap popping

Quote:
Originally Posted by special-K View Post
Welcome to the site. I've never done an LS swap and not real big on computer controlled servicing, but it sounds like one component isn't talking to the other. Something is either not connected properly, wiring issue, other bad component. There is an LS swap message board where I'm sure you'll find your best answers.

What did you do with that Olds 350?
Im going to pull everything back down and wire it all over again. It was a 355 that was in it and i sold it to my cousin.
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Old 03-17-2017, 12:37 PM   #4
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Re: 5.3l swap popping

If you replaced the sensor and it didn't help, trace the wires carefully to make sure they didn't get knicked/cut/pinched/etc somewhere.
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Old 03-17-2017, 02:57 PM   #5
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Re: 5.3l swap popping

I don't remember the details but I seem to recall having to do some type of "crank relearn"

Try searching for that.
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Old 03-17-2017, 06:00 PM   #6
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Re: 5.3l swap popping

Does the engine turn over smoothly when cranking, besides the popping of course
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Old 03-17-2017, 06:16 PM   #7
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Re: 5.3l swap popping

Double check your coil pack harness. Sounds like you may one or both backwards.

passenger side from front back

2 - pink/red/brown/black
4 - pink/green
6 - pink/blue
8 - pink/purple

driver side from front to back

1- pink/purple
3 - pink/blue
5 - pink/green
7 - pink/red
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Old 03-17-2017, 06:25 PM   #8
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Re: 5.3l swap popping

Quote:
Originally Posted by Daddy'O View Post
Double check your coil pack harness. Sounds like you may one or both backwards.

passenger side from front back

2 - pink/red/brown/black
4 - pink/green
6 - pink/blue
8 - pink/purple

driver side from front to back

1- pink/purple
3 - pink/blue
5 - pink/green
7 - pink/red
X2 on that
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Old 03-17-2017, 07:54 PM   #9
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Re: 5.3l swap popping

Did you do any internal engine work, or is this a stock pullout?

If you end up chasing a solution, you may consider a CASE relearn. This is what was being alluded to earlier. When you put a new crank sensor in, the ECM may need this done. It basically recalibrates the sensor and ECM to the crank angle sensor, and its relationship/phase with the cam sensors. If you did a cam swap, its also very possible.

The downside is that CASE relearns require command-access to the the ECM, so thats something like HPT, a TechII/III or other full feature scanner/control.
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Old 03-18-2017, 12:38 PM   #10
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Re: 5.3l swap popping

But doesn't a crank sensor alignment (or CASE, whatever) require the engine be running before they do it? So it can't be the cause of a no-run, if that's the case...

Given this sounds so much like a distributor issue (and there's no distributor) I'm leaning towards the coil pack myself as others said... we shall see what the owner says!
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Old 03-18-2017, 02:01 PM   #11
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Re: 5.3l swap popping

I'm with daddyo..when I got my engine running it had a backfire/miss to it and a couple of cold header tubes on the drivers side..I looked at the coil pack harness and it looked ok..but I also went and looked at my new trucks harness and sure enough the coil packs were wired backwards..simple swap and it ran like a charm..

Last edited by mongocanfly; 03-18-2017 at 03:46 PM.
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Old 03-18-2017, 03:00 PM   #12
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Re: 5.3l swap popping

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Originally Posted by mongocanfly View Post
I'm with daddyo..when I got my engine running it had a backfire/miss to it and a couple of cold header tubes on the drivers side..I looked at the injector harness and it looked ok..but I also went and looked at my new trucks harness and sure enough the injectors were wired backwards..simple swap and it ran like a charm..
Did you mean injector or coil? I figure batch fire used to work just fine, so having the injectors wired wrong would be sub-optimal and may not idle as well but should actually work without backfiring, etc...

Get the coil packs wrong and all bets are off though!
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Old 03-18-2017, 03:42 PM   #13
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Re: 5.3l swap popping

Dogonit..your right ..I meant coil packs..sorry..I fixed my above post..thanks for pointing it out
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Old 03-18-2017, 07:02 PM   #14
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Re: 5.3l swap popping

Quote:
Originally Posted by davepl View Post
But doesn't a crank sensor alignment (or CASE, whatever) require the engine be running before they do it? So it can't be the cause of a no-run, if that's the case...

Given this sounds so much like a distributor issue (and there's no distributor) I'm leaning towards the coil pack myself as others said... we shall see what the owner says!
Yes turns out it does. I thought your could do the relearn on cranking only, I was wrong.
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Old 03-19-2017, 03:58 PM   #15
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Re: 5.3l swap popping

Sorry fella long weekend. The truck is at the shop right now getting exhaust done on it right now. I will go through it this week and let you guys know what i found. And thanks for all the comments.
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Old 03-19-2017, 04:00 PM   #16
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Re: 5.3l swap popping

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Originally Posted by aruss99 View Post
Does the engine turn over smoothly when cranking, besides the popping of course
The engine turns over good and sounds like it wants to start. But the popping
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Old 03-19-2017, 04:03 PM   #17
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Re: 5.3l swap popping

Quote:
Originally Posted by BR3W CITY View Post
Did you do any internal engine work, or is this a stock pullout?

If you end up chasing a solution, you may consider a CASE relearn. This is what was being alluded to earlier. When you put a new crank sensor in, the ECM may need this done. It basically recalibrates the sensor and ECM to the crank angle sensor, and its relationship/phase with the cam sensors. If you did a cam swap, its also very possible.

The downside is that CASE relearns require command-access to the the ECM, so thats
something like HPT, a TechII/III or other full feature scanner/control.
The enging is completely stock. Just a tune on the computer by frost.
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Old 03-19-2017, 05:52 PM   #18
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Re: 5.3l swap popping

Did you service, clean the injectors, if it was sitting for a long time.
How is the fuel pressure?
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Old 03-19-2017, 08:43 PM   #19
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Re: 5.3l swap popping

if it sounds like it wants to start but is popping, I would double check that the map sensor is reading correctly. I had an issue similar to yours, and it turned out to be the map sensor always reading 100kpa
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Old 03-27-2017, 01:53 PM   #20
LA_85
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Re: 5.3l swap popping

Guys i just want to thank you all for your help. I had the coil harness on the wrong sides. Lol she is definitely running now.
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Old 03-27-2017, 03:37 PM   #21
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Re: 5.3l swap popping

Quote:
Originally Posted by LA_85 View Post
Guys i just want to thank you all for your help. I had the coil harness on the wrong sides. Lol she is definitely running now.
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Old 03-27-2017, 03:57 PM   #22
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Re: 5.3l swap popping

glad ya got it fixed..
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