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Thread: 99 Silverado manual, swapped to 5.3, won't start

  1. 01-28-2019 #1
    f22b2accord
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    99 Silverado manual, swapped to 5.3, won't start

    Friend of mine swapped out the 4.3 to a 5.3 on his 99 Silverado manual 4wd. He's using the 5.3 ecu, out of a 2000 Suburban, both trucks have manual throttle bodies. I flashed the truck. Removed vats and all trans related dtcs. Also set trans to manual, and under prnd, I set it to none. The starter won't engage, nothing happens if we turn the ignition switch. The starter relay doesn't receive a signal. Tried different relays, and opened the relay cover and there's no movement. Truck was starting just fine before swap. Any suggestions or tips? Thank you
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  2. 01-28-2019 #2
    5FDP
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    Setting it to manual doesn't do anything.

    You have to actually do a segment swap if you want it to be a true manual transmission file.

    Did he use a 5.3 fuse block too?
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.
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  3. 01-28-2019 #3
    f22b2accord
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    He used the stock fuse box, from the 4.3
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  4. 01-28-2019 #4
    f22b2accord
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    As far as a segment swap, how would I go about that? And thanks for replying, I appreciate it
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  5. 01-28-2019 #5
    5FDP
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    He will need to do more research but he needs to verify that things are in the same place in the fuse block from a 4.3 and a 4.8/5.3. If the wire harness on the V8 isn't seeing the correct things in the fuse block, that is going to an issue.

    Find a matching OS from a manual transmission silverado/sierra and maybe even a S10/blazer from the year 2000 like that computer is and do the segment swap. Use the compare feature and the segment swap function is in there. You can search more on that if you want.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.
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  6. 01-28-2019 #6
    f22b2accord
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    Since the ecu is out of the 5.3, and everything fuel related is from the 5.3, we're just trying to see if this thing will start. The fact that the strater isn't receiving a signal is what's troubling us. Once the truck starts, then fuel tunning will be the first thing. The fact that it's not starting is confusing to us. The fuse box looks identical, but I'm not sure if there's minor differences. The donor truck was wrecked, so I'm not positive about comparing one fuse box to another
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  7. 01-28-2019 #7
    f22b2accord
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    Also, forgot to mention, the engine harness is from the 5.3, the ecu is also from the 5.3. the truck is a 99, the donor engine and ECU are 2000, both as the 2000 body style, not the square 5.7 engine body style
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