Really long fire-up

[AndrewJReynolds85]

I have a 99 Suburban that I have ls swapped and it had a gen3 6.0 in it. It never fired up super fast, normally takes about 5-6 seconds to fire. Sometimes i have to turn the key off and let it prime again. I swapped out the motor for a 5.3 for an unrelated issue and it seems to have gotten worse. It really seems to me to be not getting enough fuel in the startup but didnt know if timing might help that as well. The motor is a 5.3 with a texas speed stage 2 truck cam. Also I am trying to figure out if the misfires I have on #2 and 7 are a concern or if that's normal.

Suburban 5.3 9-20 after smoothing.hpt9-20 drive.hpl

[blindsquirrel]

Have you confirmed it's lack of cranking fuel by priming it with a shot of brake cleaner, and not a cam sensor issue?

[Josue Galban]

I have a 99 Suburban that I have ls swapped and it had a gen3 6.0 in it. It never fired up super fast, normally takes about 5-6 seconds to fire. Sometimes i have to turn the key off and let it prime again. I swapped out the motor for a 5.3 for an unrelated issue and it seems to have gotten worse. It really seems to me to be not getting enough fuel in the startup but didnt know if timing might help that as well. The motor is a 5.3 with a texas speed stage 2 truck cam. Also I am trying to figure out if the misfires I have on #2 and 7 are a concern or if that's normal.

Suburban 5.3 9-20 after smoothing.hpt9-20 drive.hpl

Suburban 5.3 9-20 try this file, by @quickxstep.hptSuburban 5.3 9-20 try this file, by @quickxstep.hpt

try this file

[AndrewJReynolds85]

Well I finally broke down and dug through my storage unit for my Fuel pressure gauge. Looks like i have a mechanical issue. Maybe a leaking injector???? It primes but immediately loses prime. and no leaks anywhere I can see. Would this be an injector stuck open? https://youtube.com/shorts/TqbC4LuVT...5fgnndpt340oLl

[Josue Galban]

Well I finally broke down and dug through my storage unit for my Fuel pressure gauge. Looks like i have a mechanical issue. Maybe a leaking injector???? It primes but immediately loses prime. and no leaks anywhere I can see. Would this be an injector stuck open? https://youtube.com/shorts/TqbC4LuVT...5fgnndpt340oLl

look my file

[blindsquirrel]

(please ignore anyone suggesting their special tune file to fix a pump or injector issue)

Pinch off the return line to eliminate the regulator as the cause of the pressure drop. Pinch off the supply line to eliminate the check valve in the pump. If there's no change with either of those, it's probably a leaky injector. Pretty easy to unbolt & raise up the fuel rails where you can see a drippy injector.

[Alvin]

Well I finally broke down and dug through my storage unit for my Fuel pressure gauge. Looks like i have a mechanical issue. Maybe a leaking injector???? It primes but immediately loses prime. and no leaks anywhere I can see. Would this be an injector stuck open? https://youtube.com/shorts/TqbC4LuVT...5fgnndpt340oLl

Most of the time its just a bad check valve in the pump.

[AndrewJReynolds85]

Most of the time its just a bad check valve in the pump.

Well, I think it might just be a bad setup on my part but now I don't know. I have a quantum 340LPH in tank pump and a Holley 12-880 Fuel pressure regulator. Its allowing the fuel to go back in the tank. I have my inlet going in 1 side and the outlet on the other with the return on the bottom. The injectors pressurize to 60psi immediately then drop back down. I'm guessing it was exacerbated but the fact I was waiting on the laptop to connect so I could run a data-log.

[Alvin]

I assumed a stock fuel system.. Yeah a lot of aftermarket regulators do this also.

[AndrewJReynolds85]

I assumed a stock fuel system.. Yeah a lot of aftermarket regulators do this also.

Yes, It was my mistake. I was thinking it would work but this regulator is made to run after the rails not before and i am running a stock ls truck rail so I am stuck with a single inlet. Now i Need to either 1 deal with the slow start, 2 get aftermarket fuel rails or 3. Get a new Fuel pressure regulator like a corvette style. I think I am going to just deal with it lol

[Alvin]

On some OS's you can lengthen the fuel pump prime time.. That might help.. Stock is usually 5 sec I think.

[blindsquirrel]

Fuelab is the only aftermarket EFI regulator I know of that is built like a real EFI regulator that holds pressure with the pump off. Everything else on the market is just a carbureted regulator with a big fat spring in it.