LS swap 5.3

[zainestrife]

Hello All,

Been digging and looking through the forums and my search will continue even after I post this, I have a basically stock swap into my 68 skylark Deleted vats, deleted secondary 02 sensors. Had a few issues with wiring and the maf but that seems to be solved now. But as The car is running its popping and backfiring. all 8 holes are hot on the exhaust, all have spark all have fuel , I am attaching my data log and tune file . Any help is appreciated

2004 chevy Tahoe donor gen 3 5.3
evap deleted
Standalone harness,
stock computer from flagship one flashed to the vin of the vehicle
4l60e converted from 4x4 to 2wd
stock cam injectors throttle by wire

thank you in advance

41223 skylark.hpt

41223 skylark.hpl

[TheMechanic]

Verify you don't have any injector pigtails swapped. Like #6 on #8 or #5 on #7 etc.

[zainestrife]

Thanks will check out the pinning today, guess its not unreasonable that those are wrong too

[blindsquirrel]

What type fuel system, what fuel pressure? 'Cause a 2003 VIN Z file will have injector data set up for a 51 PSI referenced/return fuel system, if you have something different at a different pressure, the injector stuff needs changing to suit.

[zainestrife]

What type fuel system, what fuel pressure? 'Cause a 2003 VIN Z file will have injector data set up for a 51 PSI referenced/return fuel system, if you have something different at a different pressure, the injector stuff needs changing to suit.

Using a external holley pump PART# 12-170, pushing to the rail at 58 psi, factory pressure regulator is still there

flow is pump to rail
rail return to aftermarket pressure regulator holding at 58 dumping back to tank

[blindsquirrel]

A 2003 L59 rail-mounted regulator should have a base pressure of 51 PSI ("48-54 PSI", according to the service manual). If yours is anything other than that then it's not a L59 regulator pod-thing, it's from a non-flex return style truck. All others were 58 PSI base only the L59 flex was 51.

'Base pressure' is key on engine off, or engine running with the regulator vacuum hose removed.

[zainestrife]

A 2003 L59 rail-mounted regulator should have a base pressure of 51 PSI ("48-54 PSI", according to the service manual). If yours is anything other than that then it's not a L59 regulator pod-thing, it's from a non-flex return style truck. All others were 58 PSI base only the L59 flex was 51.

'Base pressure' is key on engine off, or engine running with the regulator vacuum hose removed.

it was a flex fuel truck, Will turn down/edit my pressures as well

[blindsquirrel]

How? Does it or does it not have a stock L59 regulator in the stock L59 fuel rail? The stock regulator isn't adjustable, the tune file already has data set up for 51 PSI. You said it's got 58 PSI, and these injectors do not flow 33lbs at 58 PSI, they flow 35.4lbs.

If you have 58 PSI base, referenced/return-style, then use the 0 kPa VAC column across your entire flow rate & offset tables from a '05-up returnless L59, as those are 58 PSI.

[zainestrife]

340456691_1449431755800651_4372245737771111246_n.jpg

Sorry, let me clarify and I am open to changing things too.

From the pump to the rail fuel is flowing freely, on the rail still has the factory regulator referenced to intake fuel continues to regulator on the firewall which is set to 58 psi before returning to the tank

[blindsquirrel]

You can't do two regulators like that. What's happening there is, the second regulator is forcing the rail-mounted regulator wide open all the time, since the one on the rail is trying to regulate at 51 PSI. If there is vacuum to the one on the rail, it's never going to reduce rail pressure when vacuum is high (low pressure) and raise it when vacuum is low (high pressure, = to atmosphere). Your second, non-referenced reg is the one in control since it has the higher set point, and you need to use injector data set up for a returnless/non-referenced system (copy tables from a '05-up L59).

Ditch the add-on reg and use the stock one on the rail by itself and you won't have to change any of the injector data in the file, since it's already configured for the L59 51 PSI referenced setup.

[zainestrife]

You can't do two regulators like that. What's happening there is, the second regulator is forcing the rail-mounted regulator wide open all the time, since the one on the rail is trying to regulate at 51 PSI. If there is vacuum to the one on the rail, it's never going to reduce rail pressure when vacuum is high (low pressure) and raise it when vacuum is low (high pressure, = to atmosphere). Your second, non-referenced reg is the one in control since it has the higher set point, and you need to use injector data set up for a returnless/non-referenced system (copy tables from a '05-up L59).

Ditch the add-on reg and use the stock one on the rail by itself and you won't have to change any of the injector data in the file, since it's already configured for the L59 51 PSI referenced setup.

I realized that after I posted it, I reduced the psi of the secondary reg down to next to nothing 10 psi maybe? and am still getting popping but I think my pump is pushing through the injectors and will need to route my fuel from tank that that regulator first

I have also realized as soon as my pump turns off the pressure to the fuel system is back down to 0

[blindsquirrel]

Again, two regulators in series like that aren't going to behave like either reg used separately. Do you have a pressure gauge on the rail (i.e. before the rail-mounted regulator)?

[zainestrife]

Again, two regulators in series like that aren't going to behave like either reg used separately. Do you have a pressure gauge on the rail (i.e. before the rail-mounted regulator)?

No I do not have a pressure gauge on the rail. I will swap my return line to the rail after work and remove the aftermarket from the circuit and fire it up again

I did just back down the after market to 2 psi and the backfire seems to be a lot less for sure

[zainestrife]

no change when going to just the fuel rail and no secondary FPR

[blindsquirrel]

This is baseline pre-startup stuff to get everything configured correctly, not chasing a solution to your specific problem. It needs everything set up and verified working before you can reliably go diagnosing problems.

[zainestrife]

I understand and appreciate all the help for sure, Didnt get to check injector or the rest of the coil pinning yesterday but I plan on doing so tonight

[zainestrife]

Injectors were all fine, Coil signal between #5 and #4 in my harness were reversed. causing the backfire, So cheap harness strikes again.

Now to solve transmission shifting issues but somehow I think the culprit is still the same

[jeremiah pistol]

coil harness can go on backwards and do as you describbed