Need Help
 

I know there has been a lot of guys here that have conversions of gen v engines into older vehicles. I sure could use some help please.


Here is what I have. 1957 Chevy truck with a totally stock 2014 L83 engine and 6L80E trans. Factory computer, front O2 sensors installed.

Factory fuse relay panel X50A, have deleted the VATS have HP Tuners and only made a few changes with the DTC’s.



Here is my problem.

Engine fires and runs very good and after a running for a while (Sometimes 20 minutes sometimes 30 to 45minutes) it dies and will not start. After a few minutes it fires right back up and runs great for a little while and then it dies again, after I let it set a few more minutes it fires again. Very frustrating.

What I found

When the engine dies I am not getting the ground signal from my computer causing the powertrain relay to open X50A pin below

Pin

H6

0.5

YE

5991

Powertrain Relay Coil Control



ECM E92 X1 pin below

Pin

72

0.5

YE

5991

Powertrain Relay Coil Control

engines shut down for a lot of reasons, the pcm supply's the ground so to see if your theory is correct once the engine starts ground that relay externally. See what happens, sounds like you have a electronic component over heating. I worked at a GM dealer as a tune up tech and could isolate modules by creating a pattern of failure and then introducing ice cold water to find the failing part. Sometimes the failures don't fit into the diagnostic envelope and you have to THINK . HST Tuned ECM's are handy-caped diagnostically. Clearly when it wont start you need to test for spark, injector pulse rpm and fuel pressure etc.

Thanks Driveability
I am thinking that I may have a ecm problem. When the engine dies and won't start I bypassed the relay and the engine will run, but very poorly. Is it uncommon for ecm's to go bad?

As I said you need to go step by step when the engine dies. You need to find out what's failing. The engine is dying for a specific reason and the engine computer is reacting to that by un-grounding the power relay. By "bypassing" and grounding the power relay your not correcting the failed sub-system. Find out what's missing when the car fails to start,( spark, computer data, injector pulse, fuel pressure etc.. could be a computer issue but guessing is a rich man's game LOL .