870 to 165 ECU, injectors pulsing way too fast

[2.8/3400 1985 Camaro]

Figure I will see if I can maybe widen the potential knowledge base and post this up here too, did an ECU swap to convert my car to DIS, the DIS part is working just fine, plugs are firing great, but for some reason my injectors are pulsing too fast, I have a thread started on the TGO forum already, so I will just link to it:

http://www.thirdgen.org/techboard/dfi-ecm/626333-870-ecu-165-ecu.html#post5026329

[pocket-rocket]

That guy on TGO may be onto something with the v8 code.

The nitty gritty:

My memcal doesn't have any kind of cover on it, is it possible the bin it had, was erased by sunlight and it reverted to its original bin maybe?

Short answer, no. Not possible, well, to an extent. The information on the chip (the .bin) is erased by UV light, so it's possible (if the chip sat out without the silver sticker for a long time, the sticker is what covers the UV window on the chip) that the sun could erase the chip, but it's not going to revert back to the original bin without the aid of a chip burner.

yeah see, I am missing that cover piece, so I guess I don't have that #...but he sent the ECU as complete ready to run and preprogrammed.

You don't need the blue cover, the silver sticker with the BCC is right on the chip covering the UV erase window. If you don't have the sticker and you don't see a window, it's possible that the original chip (EPROM- Erasable Programmable Read Only Memory) has been removed and replaced with a new one (EEPROM- Electrically Erasable Programmable Read Only Memory). When tuning OBD1 the old fashioned way people do this and let the chip burner erase the chip in seconds before writing the new code to it. Otherwise it takes 10-15 minutes in a UV light chip eraser, and you only get a few burns before the chip can go bad, vs probably thousands of erase/write processes with an EEPROM.

If you do not have the sticker and it's an EEPROM, you are going to have to either buy your own, or find someone local, or semi-local, or mail your chip to someone to have it read so the BCC and code mask can be found out to determine which code is being run on that ECM.

I'm kinda curious how you know the injectors are firing too fast, though...

[Superdave]

Sunlight, unless concentrated and focused onto the window of the eprom will not erase the information and even in that case the heat of the IR band would cause the chip to fail before the UV band would erase the info.


the UV bulb in a chip eraser is extremely powerful. It's badass enough to give you skin cancer in a matter of minutes. I have one and it takes roughly an hour of exposure to erase a 27C256 chip.

[pocket-rocket]

An hour huh? Odd, Ben must have had a very bad to the bone one because I could have sworn his did it in about 15 minutes.

Also, OP, you do know your car was made to run in batch fire mode, right? Old multiport engines were set up to run in batch fire, where all injectors fire at once, not separate like sequential injection on the newer engines.

[Superdave]

I'm thorough with the UV eraser, it might actually take less time but it's annoying when you have one that doesn't blank check.


I get 27C256 Eproms for free from work, usually with just 1 burn on them so that's what i sell all my tunes on.

[2.8/3400 1985 Camaro]

I know its pulsing the injectors too fast from a test light you plug into an injector connector, kind of like a spark plug checker. And yes I know its batch fire and not SFI, question about its batch firing though, does it fire in cylinder banks, or ALL injectors at once? And either way its still most likely the cause, I suspected the problem was fuel ever since the swap, and a spark plug checker showed that the DIS end of my conversion was a smashing success, which doesn't leave much else to question, especially with a new fuel pump, and filter and no leaks in the lines.

[SappySE107]

all at once, not bank. Its either the tune or the wiring, but I didn't read the thread:P My UV eraser took 15min or the chip never would erase, either way:P I am done with 27C256.

[Superdave]

datalog.......