TBI Injector Not Firing... With a twist.

**churchill.samuel** · 2 Weeks Ago

I recently have been trying to switch away from a Microsquirt ECU on a 383 TBI, putting the old 7427 PCM back in and acquired all the chip burning hardware. With the MS (Microsquirt), I had it running and driving pretty good, but putting the original PCM back in (and changing the Displacement per cylinder to a 383 in the Binary file) it ran terrible and would not drive in gear. The O2 was reading rich then lean back and forth, nothing crazy, but adding more throttle after 5% made no more power and sounded horrifically lean. I popped the lid off the air cleaner and the passenger side injector was not spraying at all, Driver side was fine.

The thing is that if I put the old MS setup back on, both spray as normal and drives fine. I don't know if its a hardware problem or tuning problem but it is driving me up a wall. Does anyone know what the heck is going on? I've compared my modified bin against the original BJLF bin for a 1994 Blazer L05 4l60e and I didn't change anything other than Displacement constant, VE, and EGR. I'm probably going to open up the PCM case and have a look but wasn't sure if this was a known issue or not.

**dave w** · 2 Weeks Ago

I think hardware.

When using the 16197427, have you tested the injectors with a Noid Light?

**churchill.samuel** · 2 Weeks Ago

Never heard of a Noid Light. I will look into that and pick one up.

A side question that I can't seem to find info on. When swapping chips to burn, do I need to disconnect the battery every time or can I just remove the fuse to the ecu?

**In-Tech** · 2 Weeks Ago

Noid light kits,
https://www.rockauto.com/en/moreinfo...001027&jsn=328
https://www.rockauto.com/en/moreinfo...001027&jsn=330

I am 99% sure pulling the fuse is just like key off. I always unplug computer for a couple mins(or disconnect battery) to clear any ram stored in the ecu.

**dave w** · 2 Weeks Ago

I've been lucky several times swapping chips with just the ignition switch "OFF". It's a personal risk factor, so how do you really feel about swapping chips with (Battery +) ~ (Battery -) still connected to the computer? Electrons are lazy, they take the path of least resistance.

I learned long ago the basic rule about how everything electronic is smoke powered, DON'T LET THE SOMKE OUT of electronics.

**In-Tech** · 2 Weeks Ago

Originally Posted by dave w

I've been lucky several times swapping chips with just the ignition switch "OFF". It's a personal risk factor, so how do you really feel about swapping chips with (Battery +) ~ (Battery -) still connected to the computer? Electrons are lazy, they take the path of least resistance.

I learned long ago the basic rule about how everything electronic is smoke powered, DON'T LET THE SOMKE OUT of electronics.

The chips run on magic smoke, if you let the smoke out, no more worky

Yepper, plenty of times I will just swap a chip with the key off. The emulation stuff can get a bit weird at times though. The clearing ram thing is mainly if things have gone fubar. If I can, I pull the + cable and hold it to the negative to drain everything quicker.

**churchill.samuel** · 2 Weeks Ago

Ok thanks the replies. Ill pick one of those kits up and try it out. Ill probably also just pick up another PCM too because even if I get the original going, I have some other trucks with the 7747 that could use the newer computer.

Yea I'm surprised I haven't seen many people mention anything about taking power off the ecu in chip swapping related threads. Must not really be a problem.