5.3 SWAP Wiring Problem

[Clyde65]

I dont know if this will help you but my swap had the same issue, however when I found one of the W4Me supplied harness power needs was a constant 12v through the key on and start process was lacking, I put one from the fuse box and it started and ran. I used the W4Me harness and sort of stock truck harness along with the fuel pump and fan relays. Hope it helps.

[eagleuh1]

What fuse box are you using in the engine harness. Theres fuses for the injectors and coils and other various systems in the engine harness. It requires some kind of fuse box such as the under hood fuse box from the donor vehicle or an after market one from Current performance. Check the fuses in this fuse box to verify good, or there/installed.

[sick454]

Originally Posted by eagleuh1

What fuse box are you using in the engine harness. Theres fuses for the injectors and coils and other various systems in the engine harness. It requires some kind of fuse box such as the under hood fuse box from the donor vehicle or an after market one from Current performance. Check the fuses in this fuse box to verify good, or there/installed.

W4m said all i need is the 15 amp fuses on the pigtails they intalled and a 10 amp fuse on the white constant power to the PCM. There are no Fuses to the coils, or injectors other than these.

[68GMCCustom]

you can send your PCM and VIN to a good tuner...and they will put the factory loads for your VIN into the PCM...once thats done, they tune it for your individual needs (fuel octane, elevation, reduction of torque management, etc.) before returning it to you. With this done a crank relearn shouldn't be necessary.

ALL of this is one of the reasons I am putting a carb on my LSx.

[sick454]

OK here is what happened, Went and got a Scanner and the only codes it's giving me are the HO2S Heater codes. And that should not keep it from running. (P0030, P0036, P0050, P0056) I asked WFM to remove the two they recommended to remove (the back, I think), and still nothing. Jesse swears there is nothing wrong with it. I am severly frustrated! Then he wants me to go buy 4 O2 sensors and leave them hanging to see if it will start then??? They are a little expensive for me to just experiment with them.

[sick454]

Alright, I went out to double check, I only have two O/2 sensor plugs (W4M remove the two rear ones) but the Scanner is giving me four 0/2 codes. unplugged the MAF sensor and still nothing. Anyone with ideas? Thay haven't been discussed thus far?

[eagleuh1]

OK, he's got inline fuses installed. No bulky fusebox to look at then. Check to verify theres actually a fuse installed in the holder, and that it still is good. Have you checked to verify you have power on the circuits that energize when the ignition key is on and also in the crank positon. It will go through a relay to energize these circuits. With an aftermarket harness I don't know where'd he'd put this relay, but verify it's working. It sounds like it is if the injectors are cycling, but he may have them on seperate relays.

[eagleuh1]

If you can get some noid lights from somebody, you can check to make sure the injectors are all cycling.

[Clyde65]

Like I said and Eagle said, one of those wires that W4Me supplied needs key on 12v even when cranking so it will run, I will need to look when I get home to see which wire it was on mine. I would call W4Me and ask which one needs that kind of power to it.

[sick454]

OK, First, I WAS WRONG. There that's out of the way. It started. Come to find out I had the fuel pump wired backwards. I knew it would be something stupid and easy. and it was. Each terminal is different sized. Ones large and one is small. Naturally I assumed the Large on was the positive. I was wrong (dang said that twice) the little one is positive. Once I swapped it. It fired right up.
Now to hook up oil pressure and water temp gauges and then a trip to the muffler shop! IT's LOUD!!!

Oh and yes it was labeled which was positive and negative, however at 10 pm on a saturday night, under a truck, in the dark, it's hard to remember to look and verify it.

I wanted to Thank everyone who chimed in and offered help. they were all great idea's. Now on to the next step!

[Clyde65]

I did the same thing......I completely understand how that could be missed.

[glock35ipsc]

I'll have this moved this to the LS swap area for future reference.

BTW, when I tried to start mine for the time, I also had fuel but no spark. Turns out the "key on" wire I had chosen to trigger my ignition coil relay had 12v when the key was in the "run" position, but lost power when in the "start" position. Changed the trigger wire to one that had power in both "run" and "start" and it fired right up.

Glad it finally started for ya!

[eagleuh1]

Awesome, glad you got it figured out and was something so simple and cheap to fix. How bout some pictures now.

[Ackattack]

Originally Posted by glock35ipsc

I'll have this moved this to the LS swap area for future reference.

BTW, when I tried to start mine for the time, I also had fuel but no spark. Turns out the "key on" wire I had chosen to trigger my ignition coil relay had 12v when the key was in the "run" position, but lost power when in the "start" position. Changed the trigger wire to one that had power in both "run" and "start" and it fired right up.

Glad it finally started for ya!

I had the exact same thing when I was doing my TPI swap, but occasionally, the engine had enough inertial to spin enough, that when I let off the "start" back to the "run" it would fire up.....that had me stumped for a week!



Glad you got it fired up

[tk-mpl]

I feel your pain, it took me 3 weeks of more then just sundays to get mine going. I rewired and reprogrammed with EFI Live myself. Went to start it and had no injector pulse and no spark. I rechecked every pin on the ECM and traced a lot of the wiring... LONG story short I reflashed it with a different vin and it started right up........ But man, all the hate was gone when the sound of open headers scares the crap out of you.......

Trevor

[faribran]

its good that you guys share this kinda info.... will be helpful to others down the road...
this makes the challenges more fun.