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** · 1 Week 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** · 1 Week 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** · 1 Week 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** · 1 Week 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** · 1 Week 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.

**1project2many** · 1 Week Ago

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

You know, I sent bags of that stuff to Doc and the little guys at CSH HQ. Not sure if it helped them get their 747 off the ground but I'm sure they had fun trying.

**1project2many** · 1 Week Ago

Originally Posted by churchill.samuel

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.

The chips used with the 7747 are especially susceptible to static shock. You should use a ground strap when swapping chips.

**churchill.samuel** · 1 Week Ago

I am still waiting for the Noid light in the mail, but I have been trying other things to get a better idea what the most likely culprit is. I purchased a used 7427 to try that in the event that was the issue and if it wasn't then it would go in another truck to upgrade from a 7747. Tried the new computer/memcal and no change, put the Megasquirt setup back on and again both injectors spray away with a good pattern as far as I can see. I put the original PCM back in and swapped the wires to the opposite injector and same issue except that the "bad" injector now started working intermittently, mainly when I blipped the throttle and sometimes when it's about to die it will start spraying and rev up making a surge. When it does spray, it looks like I can see some dripping inside the cone of fuel.

I'm starting to narrow in on the one injector needing replaced or cleaned, but the puzzling thing is why does it work with my Megasquirt setup? The only thing I can thing would be if the Megasquirt along with my 6 ohm power resistors are delivering enough amperage to open the dying injector.

I was looking and I've seen people recommend MrInjector.com to clean and flow injectors, has anyone had experience with them or know of a reputable cleaner?