5.3L LS won't fire
 

Hey gang,


Has anyone here had any experience getting a LS system to fire?

I have a 2008 5.3L just installed into my '57 stepper with the DOD now removed, new cam and lifters installed by a GM tech and a FiTech Ultimate LS injection system installed. FiTech says all their wiring is correct, but no fire to the plugs.

Thanks,

Ken

Re: 5.3L LS won't fire
 

The instructions are pretty straight forward https://secureservercdn.net/198.71.2...ctions-v.2.pdf

You did properly ground the ignition ground # 6 in fig 13 ? Good tight ground to clean bare metal?

if that was an original V8 truck with the stock ignition switch I'm thinking that the switch doesn't power to the coil (ignition) when you crank the engine depending on the resistor bypass to provide power to the coil. Meaning that you may not have power to The "red wire" for the igniton or even to turn the Ecm on when it is cranking.

Take a test light or volt meter and connect it to the red wire and have someone crank the engine and see if you have power when you are cranking. The red wire being #4 in fig 13.

Re: 5.3L LS won't fire
 

Good grounds are crucial... the frame was powder coated so that's a real possibility for the issue. The 57 is a V8 truck but has a frame off rebuild now with the addition of the 5.3L power plant, so it's all new.

Re: 5.3L LS won't fire
 

Beautiful truck..does sound like you need to start with the grounds..
I'm not familiar with the Holley setup, but you should have a 12v constant feed,a switch on 12v feed to the ecm, and the grounds..who flashed the ecm ?

Re: 5.3L LS won't fire
 

Researching the Ultimate LS setup last night it is a stand alone with it's own ECM and doesn't need the oem ECM. This is probably the unit he has. https://fitechefi.com/product/ultima...3-port-intake/

Re: 5.3L LS won't fire
 

Thanks! Pretty excited to get it done. Sadly, I'm currently at the mercy of the body shop finishing the build. They have exhausted their mechanical capabilities so I've told them to finish the rest of the areas they can and get me the truck and I'll work on getting it fired up.

pretty close... mine is the 70004, 500 HP version.

Re: 5.3L LS won't fire
 

First is what everyone else has said. Check all of the grounds.

Second, make sure the 12v ignition is still 12v when cranking. I installed a 5.3 with the Fitech in an '86 Cutlass and it would show 12v with the key on but not while cranking.

Once I found a different source for the 12v that stayed constant while cranking it fired right up.

The Fitech systems are okay but their tech support isn't very good. You can also check on https://ls1tech.com/forums/conversions-swaps-28/, there should be a lot of info on these systems there.

Re: 5.3L LS won't fire
 

this is likely it. the key switch wire diagrams are not intuitive and skymangs had this exact problem with his ls swap, he had ign 1 and ign 2 swapped and ign 2 had no power when cranking. i dont know why they call it ign 2 when it should be labeled acc.

Re: 5.3L LS won't fire
 

I too was tripped up on the 12v "while cranking" on my previous EFI build. It is usually the simple things.

Marc

Re: 5.3L LS won't fire
 

It looks like several of us have run into this same problem over the years.

Meaning that that truck is designed to get power to the coil through the resistor bypass on the solenoid when you are cranking.

My experience was on a well tuned truck that the bypass wire got left off for one reason or another. You would crank it and it didn't fire but it would fire when you let off the key but just let it go to the on position.

What you may have to do is install a "start" button that acts as a resistor bypass switch when you are cranking the engine. Maybe one that is hidden under the edge of the dash were you can get it with the tips of your fingers. Or wire in a relay that works off the start pole of the switch and provides momentary power to the red wire.

Re: 5.3L LS won't fire
 

Thanks everyone. I'll concentrate on 12v and grounding issues.

/Ken

Re: 5.3L LS won't fire
 

I just went through this with a Holley Terminator X install. I thought I had grounded but then found a bad ground that messed the whole system up. I checked by running a good thick ground wire straight from the battery to the harness even if temporary. The two areas being discussed for the LS are those two ground wires near the coils. There could be more of them in the harness. Mine ended up being the in cabin one connected to the ECU.

Re: 5.3L LS won't fire
 

common ignition switches have 4 positions:
off
accessory (usually just radio)
run (with power to ign and all accessories)
crank (with power to ignition)
When you crank your car the radio, wipers, heater etc all stop working until the key returns to run. So obviously your ecm and fuel pump need to be powered on crank.

to illustrate, the picture below is the ignition switch connections for the ~86 camaro with tilt column I used in my truck. I'm not sure what purpose the wires that go to ground on crank have, I ignored them.
Attachment 2223733

Re: 5.3L LS won't fire
 

nice tips lee. looking at his project though, he doesnt have a column ignition switch. its the in dash switches that label the poles IGN 1 and IGN 2 but they dont tell you that IGN 2 is actually ACC. so you wire it up as IGN and it turns off during crank.


its the NSS or the park signal from a floor shift.

Re: 5.3L LS won't fire
 

I figured it was probably something like a ground or other connection. Maybe an ECM or coil pack, but it's system wide. The FiTech unit is new though.. so, we'll see what happens this week.

Thanks everyone!!

/Ken