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Old 06-30-2015, 07:02 PM   #1
Jonboy
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No start help after swap; 2008 5.3

Checking to see if some of the gurus here may have any help for me. I swapped a 2008 5.3 (non flex fuel) into a '77 C10. Used an aftermarket stand alone harness with a "tuned" PCM. I am having a no start issue. Fuel is 55 at the rail during prime, moves from 55 to 65 during cranking (assuming that means the injectors are firing?). New Delco plugs; have a bit of a burn spot on them, but not complete. Compression on all cylinders, anywhere from 160 to 170. I pulled the injectors and let them soak in a container of Seafoam thinking they might have been clogged. I am getting spark on #1, and there is signal at the injector plug verified by a noid light. I do have power on the switched power wire during key on and crank, constant power is good.

What could I be missing? It doesn't even act like it wants to try and start.
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Old 06-30-2015, 07:15 PM   #2
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Re: No start help after swap; 2008 5.3

Watching !!
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Old 06-30-2015, 10:53 PM   #3
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Re: No start help after swap; 2008 5.3

Will it try to start with a bunch of starting fluid? If so you may just have a bunch of air in the fuel rails that need purged.

Your tuner may have also not properly deleted the vats. On the newer ecu, he needs to do a write entire and not just write calibration the first time. If you are adjusting the tune the rafter, you can just write the calibration.
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Old 07-01-2015, 11:26 AM   #4
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Re: No start help after swap; 2008 5.3

Sounds like VATS is still enabled. Also with everything powered up does the throttle operate correctly?
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Old 07-01-2015, 09:07 PM   #5
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Re: No start help after swap; 2008 5.3

Try groundi g the case of the computer it self mine wouldnt starr and i ground the computer case and it started right up
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Old 07-01-2015, 11:31 PM   #6
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Re: No start help after swap; 2008 5.3

Will the VATS let it start then die, or will it not start at all?
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Old 07-02-2015, 03:06 AM   #7
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Re: No start help after swap; 2008 5.3

Both honestly. Sometimes VATS won't let it run at all, other times is will allow up to 7 seconds. Usually the first time after a battery reset VATS will allow the longer run, once it fails it will usually only allow it to sputter then die without really ever "catching".
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Old 07-02-2015, 07:54 AM   #8
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Re: No start help after swap; 2008 5.3

Did you turn engine over with the fuel rail and injectors pulled, to see if they are spraying?
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Old 07-02-2015, 09:23 AM   #9
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Re: No start help after swap; 2008 5.3

Quote:
Originally Posted by truckdude239 View Post
Try groundi g the case of the computer it self mine wouldnt starr and i ground the computer case and it started right up
That may be true for a stock computer but my VATS has been turned off and it is sitting on the floor on top of carpet and no ground from the case to the chassie/engine and the engine does what it is ment to do.

I am glad I did not read this before I tried to start the engine as I would have placed a ground from the case top the engine.

Thanks for bringing that info up I will add it to my trouble shooting log
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Old 07-02-2015, 12:40 PM   #10
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Re: No start help after swap; 2008 5.3

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That may be true for a stock computer but my VATS has been turned off and it is sitting on the floor on top of carpet and no ground from the case to the chassie/engine and the engine does what it is ment to do.
The ECM is internally grounded through the wiring harness. You only ever need to ground the case if the internal grounding circuit died. (It happens more than you'd think actually). The direct-grounding of the case is just the easiest way to check for it.
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Old 07-03-2015, 10:11 AM   #11
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Re: No start help after swap; 2008 5.3

I have not had a chance to check throttle actuator yet. I usually only to get to work on it at night, after the kids go to bed. I was going to pull the rails to check injector pattern this weekend. Since the noid light lit up, it led me to believe they were firing.
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Old 07-08-2015, 05:57 PM   #12
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Re: No start help after swap; 2008 5.3

Throttle actuator is working. I can hear it moving, and verified it via scantool. I did an injector balance test, and fuel pressure only dropped on one cylinder (#7). I was able to get a set of injectors from a buddy, and swapped them in. It fired, but runs really rough. The newer set of injectors sat for a while as well; it may just need to run some fuel through them to try and unstick them. The truck has no exhaust on it, so I will mess with it more this weekend. The only time I really get to work on it is after my kids go to bed.
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Old 07-11-2015, 08:43 PM   #13
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Re: No start help after swap; 2008 5.3

I would put my exhaust on before I messed with it any more....
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