kennymac16

Hi all,

First time posting to this forum but have been reading for years. Truck is a 1971 C10 with a 58x 5.3 and 6l90 swap pulled from an identical running and driving truck. Trying to start the truck and it will crank well, sputter sometimes or start and only run for a few seconds then die. Will start and run on spray. All wires have been triple checked and grounds are clean. Injectors have 12v with key on and 9.5ish while cranking, both banks. Crank sensor has around 5v key on and cranking. Just replaced the crank sensor as well. VATS has been deleted since the swap was pulled from a running and driving truck. At a loss here.

Any help is appreciated.

33willys

iTrader: (1)

Back to basics. You have spark because it runs on spray and timing but it appears fuel is the issue. How long did the engine set before you tried to start it? Maybe clogged injectors. What is the fuel pressure?

tommy49

I had a similar issue when I moved my battery to the trunk, a voltage drop to the fuel pump during cranking. I wired the pump directly to the battery with a relay. Problem solved.

kennymac16

I will try that! Thank you

kennymac16

I took the injectors off and pulsed them with carb cleaner and a 9v battery. All sprayed well. The fuel pressure at the rails is 55-60 psi and with the return line plugged over 90 psi.

Quito195

MAP sensor good/plugged in? I fought one a few years ago that was similar and that was my culprit.

kennymac16

Yes I checked that out as well

mrvedit

Since your engine runs with starter fluid, we only need to consider the fuel system and perhaps the PCM. Since you say you have 58 psi fuel pressure, about all that left is Injectors, wiring and PCM. Personally I would next use "Noids" to see if the injectors are firing. If you are sure the injectors have +12V and Ground, then only the wiring to the injectors and the PCM are left. Your first post made me wonder if VATS was killing the engine after a few seconds; I don't know if VATS only turns off the injectors or also the coils. You say VATS is turned off.
I would determine which fuse supplies power to the injectors and replace it, or verify you have +12V to the injectors when the engine is running with spray.

dw456post

Are you using the GM harness and fuse block out of a Silverado?---Or something else?
What computer?

tommy49

Did you solve this? Inquiring minds want to know!

mrvedit

For anyone reading this in the future to help diagnose why their LS engine won't start, here is a related thread:
https://ls1tech.com/forums/pcm-diagn...n-t-start.html
(As of March 1, 2024, he hasn't figured it out yet either. Hopefully we can help get both solved.)