5.3 Ignition starter wiring

[71chevystep4x4]

So I finally got my 5.3 started last night for the first time, but ran into a strange issue in the process. I had been fixing all of the minor issues with the fuel system for the last two days, and trying to start it along the way. It would crank over with everything working correctly but wouldnt start. So in the process of checking everything over, I hooked a remote starter up from the battery to the starter sylonoid. As soon as I hit the trigger on it, the engine fired up instantly. After turning it off and trying again by ignition, no start. Hit the remote trigger straight from battery, fires up every time. So what's the deal with my ignition not starting it, there's nothing to it???????

[ls1nova71]

Is it in park or neutral? If by starting it at the starter you would be bypassing the neutral safety switch. If it was cranking before and now it doesn't that's whjat I would think. Just a thought.

[BR3W CITY]

Assuming VATS has been removed; is your ignition hot through the switch, or do you have the switch through a relay down to the starter? You could either be putting too much current through the ignition switch (seen that done, but not on a swap), or just have a bad/wrong/wrong wired relay.

[71chevystep4x4]

It cant be the nuetral safety switch, Im running the orriginal sm465 4 speed tranny and removed all of the tranny wires from the harness. Otherwise, all there is to the starter is the + battery cable, and the purple ign wire from the truck that has been there since she was assembled in 1970.

[ls1nova71]

If you're getting power on that purple wire at the starter, then it sounds like the starter solenoid is bad. At least on the older starters that was the case. I remember starting my Nova with a screwdriver across the terminals when the solenoid would go bad. That was the original 350 though but I would think the newer starters would be similar.
Posted via Mobile Device

[71chevystep4x4]

I wonder if it could be the opposite, and that the purple wire isnt supplying enough juice to the starter? It cranks over just fine by ignition, just wont start. As soon as I hit it with the remote starter switch, fires off instantly. Is it possible its not cranking over fast enough by ignition? I cant tell how fast it turns over by remote, because it starts right away.

[ls1nova71]

I suppose that's possible, but I wouldn't know why it wiuldn't be putting out enough power, since you said you didn't do anything to it and it has been starting the truck for 40 years? Put a voltmeter on the purple wire and have someone crank it and see how many volts you're getting. Maybe you've got alot of resistance in your ignition switch?

[ls1nova71]

Ok wait! I just re-read your posrt and you say it cranks over fine but just wont start? Yiou're losing power to the PCM when you turn the key to the crank position. What wire are you powering up the LS harness with? should be the old wire to the distributor.

[rmvlt1100]

Originally Posted by ls1nova71

Ok wait! I just re-read your posrt and you say it cranks over fine but just wont start? Yiou're losing power to the PCM when you turn the key to the crank position. What wire are you powering up the LS harness with? should be the old wire to the distributor.

I had the the same type of problem, mine would crank but not start. I did not have one of the pink wire from the computer to a cranking circuit.

I believe it was;

Pin 19 and 75 - Pink - 12v+ KEY Power Source to PCM. Hot when Key is in the ON and CRANK positions in the blue connector.

This is web site that I used to convert my harness;
http://www.lt1swap.com/2000harness.htm

It was a pain for me at first but then everything came together and it works great. I love the LS engines.

Good luck with the conversion,
Robert

[71chevystep4x4]

yeah thats the same site I did my harness off of as well, and I have ALL of the pink wires running off of a 12v key power source. So I'm thinking that the PCM loosing power upon ingnition makes pretty good sense. I have it set up with the main power wire from the harness goes to the junction block, along with the main truck power wire, then I have a wire run from the RADIO ign plug on the fuse box, that goes to the harness' ign relay that turns on all the pink Keyed 12v. I wonder if that ign wire isnt big enough????? I'm pretty sure that's were I ran my old distributor wire from, it's just been 3 1/2 years since I yarded it out.

[rmvlt1100]

Originally Posted by 71chevystep4x4

yeah thats the same site I did my harness off of as well, and I have ALL of the pink wires running off of a 12v key power source. So I'm thinking that the PCM loosing power upon ingnition makes pretty good sense. I have it set up with the main power wire from the harness goes to the junction block, along with the main truck power wire, then I have a wire run from the RADIO ign plug on the fuse box, that goes to the harness' ign relay that turns on all the pink Keyed 12v. I wonder if that ign wire isnt big enough????? I'm pretty sure that's were I ran my old distributor wire from, it's just been 3 1/2 years since I yarded it out.

Either 1 or 2 of the pink wires need to get power while cranking. The other wires can go to ignition only. I'm not sure how the ignition switch is on your truck but mine had a wire coming off the ignition switch that had ignition power while cranking. Also you can try to find cranking power in the fuse box while cranking the engine but it is a pain with 1 person. I will look at mine and tryto get a picture or where my wire or wires are connected.

[ls1nova71]

Pretty much all the ignition wires need power while cranking. Especially the coils and injectors. Not to mention the fuel pump. The ignition relay needs to poewr the whole harness up. The wire that originally went to the coil is the easiest way to do it.
Posted via Mobile Device

[71chevystep4x4]

Now if I remember correctly, when I first put a small block with HEI distributor in her years ago, I had a friend that was amazed it ran with such a small ign wire going to the HEI, and suggested I run a thicker AWG wire to it. Maybe this is the same case, just PCM compared to HEI????

[ls1nova71]

The radio WILL loose power when cranking. This is your problem. It powers up when you turn the key to ON... but as soon as you go to CRANK it looses power..
Posted via Mobile Device

[71chevystep4x4]

Allright, so the reason that caused this confusion, and after checking all of the other fuse panel terminals, I cant find anywhere to plug into that isnt hot at all times, or that doesnt cut power while cranking. I dont remember which one I used to plug my Distributer into, but does that mean somethings wrong with my fuse panel? I just cant find a ign power supply that stays on while cranking.

[ls1nova71]

Where do you have your LS harness fuse box mounted? Is it in the cab or under the hood?

[71chevystep4x4]

under the hood, its just the typical four fuse block with ignition and fuel fump relays.

[ls1nova71]

In this pic, the pink wire in the second slot down on the left is the wire that used to go to the coil, I took the resistor wire out and replaced it with a regular wire, but this stays hot while cranking.

[howell57]

Trying to marry starter wires to new L83. Instructions on wires says that the red wire goes to starter and the pink wire goes to ignition. I hooked a battery up to main red wire (old wiring) and turned ignition key to find out what wire was going to the purple wire and got nothing. The pink wire powers the computer and turns everything on and I thought that the start position of the key would power the solenoid. Old SBC guy and this new engine is a huge learning curve.

[71chevystep4x4]

Allright, thanks man. It's just been years since she had a coil with the straight six, then followed by a small block, big block, and now this 5.3L. Have a hard time remembering how all the previous were wired:-)

[68GMCCustom]

Originally Posted by 71chevystep4x4

Allright, thanks man. It's just been years since she had a coil with the straight six, then followed by a small block, big block, and now this 5.3L. Have a hard time remembering how all the previous were wired:-)

I hear ya....mine's had the 305 V6, a 305 V8, a 383 V8, an LSx in carb'd config....and now LSx in efi config. And yup...lots of wiring changes!

[JMac11]

LS1..... you are running all "key on" funtions through that wire? I plan on doing mine that way, new packard 56 and 10 guage wire. That circuit is fused in the factory block?

Thanks
Josh

[ls1nova71]

That's the wire that originally went to the coil, pretty sure it's not fused since it comes straight off the ignition switch. I'm using that wire to power up the ignition relay that powers up the whole 5.3 engine harness.
Posted via Mobile Device

[preciador6]

subscribed having same prob.

[mongocanfly]

Unless its different than mine,I just reused the original starter wires from the sb on the ls starter
The switch on wire that went to the hei I wht I used for my switch on power