Gordonm

This is just pure lunacy. New battery and it turns over but no fire just like previous. Now this morning I am getting no injector pulse. WTF!

SteveG75

Can you get a different computer to try?
I had a problem with my FAST XFI caused by me connecting the computer ground before the big ground to the battery with the door open. The door light circuit grounded through the computer and ended up frying the IAC controller. It ran by badly since the IAC was not working.
Possible that a ground issue did something to the ECU.

cardo0

Well it is a GM PCM and it does have OBD II trouble codes - if you can access them. Does your conversion have an ALDL port? If so you would need the correct software also to scan your PCM. If the PCM shutdown your fueling you would definitely get a hard code. But without a scan tool and a ALDL OBD II port you will never see the PCM diagnostic code. I apologize I am familiar with OBD I but not OBD II so I can't help you with OBD II software.

I want to say something you may already know but a OEM computer looks for all the normal stock sensors and their information and if you don't have all those same sensors you need to somehow dummy those signals to the PCM. My research tells me a PCM will enter a limp home mode when it has the right trouble codes. I really don't know of any codes that will kill fueling (at least I can't recall any). My suspicion tells me a failed PCM would do that.

There are a lot of stand alone aftermarket EFI that are becoming simpler to use and allow you to choose what you want use for sensors and accessories. I know they're not cheap but for carburetor'd conversion they seem to make better sense than an OEM PCM conversion. I think you have quite an investment in the LS conversion itself and while changing PCM's again would be painful it might be what you need.

Hope this can help more than it hurts.

Gordonm

The stock PCM has been recalibrated to eliminate al the un needed sensors. All the VATS and the rear O2 sensors have been eliminated. It has worked very well previously to this. It has fired up and run pretty well. It does have an OBD port and no codes are there. I have a cheap scanner so it does not have diagnostic but it will read codes.

cardo0

But I have to say OBD II has plenty of DTC's for fuel metering: P005-P007 (fuel shutoff valve), P0200-P0212 (injector circuit open) and computer open circuits P0600 series, fuel injector supply voltage P2145-P2157, ECM/PCM power P2505-P2511. My guess is when the vendor re-calibrated the computer to dummy out stock sensors it blocked many or all codes also, or else your code scanner is not up to the task. We know your getting spark so it has lost fueling. Bad fuel pump or bad PCM/ECM is whats left.

Wee

I'm going to give some old school advice that I'm sure you are aware of.....Check all this out in the dark to see if you can see any sparks/arcing....Just like check old plug wires for arcing. I know that is a long shot but if there is a connection issue somewhere it might rear it's ugly head.

Good luck and it looks great....
Brian

Kacyc3

When you checked fuel pressure were you trying to start it or just key on engine off? The fuel pump may be going out and not providing enough pressure while cranking but still shows 58 psi while the injectors are closed. You need a scanner that shows live data to see what the ecm is seeing. My favorite test to try is to disconnect the tps and start it.

F22

Thanks to you, folks with far more knowledge about modern vehicles, to help Gordon out. I'm still watching this thread, just to see how it turns out. Still rooting for Gordon to keep at it and tell us what he finds, when he finally gets the fix in.

kossuth

Are you getting solid 12 DC power to the injectors? Are you certain it can carry a load? If you are certain of this and if your 100% sure on the grounds then I would get a scope and back probe an injector plus also grab the PCM signal off a coil and go from there. If you for sure have no signal on a scope grab the crank and PCM signals. Something is amiss. Given that it ran before I’m wondering if you indeed burned out the PCM driver for the injectors.

Gordonm

I’looks be jumping back on this in another day or two. Still have family in but the wedding was just awesome. My brother in law brought up a computer and complete wiring harness for an LS3 to try some things. So I have a few more ideas to try.

bmans vette

Good luck Gordon.
Nothing worse than chasing gremlins, which is why I despise electronics. I am better at mechanical stuff.
I am sure You will get it right.
Happy Father's Day btw....

ajrothm

IF you are not getting any flashes on the noid lights, then the injectors are not getting the ground signal from the PCM. Therefore, its either the injector harness has an issue (like the 12v/neg wires are touching in the harness), or the PCM is flawed. I have had both issues, personally, on my C5Z, Injector wires were taped together from the factory in the harness, yet rubbed a hole in each other, inside the harness, where it drops behind the head. Also I had a PCM that took the tune, showed the tune, would prime the pump yet would never fire the injectors, and the one time it did, it locked one open and filled up a cylinder full of gas. Another thing is your injector harness, if its a modified stock harness, may have ground loop/wire that grounds on the back of the head on both heads,... If you leave that off, no injector firing... Ask me how I know.

Just a few things to check.