83 Crossfire TA

iTrader: (2)

I have an '87 Trans Am with a factory TPI (LB9 305), and I have an MS2 PCB 3 plugged in using the adapter board (basically a plug in + vacuum line). I set the basic settings as best as I remember/can find and I connect, see basic (and reasonable) values... the car cranks but doesn't even try to start.

FWIW, I've done this before (87 Formula 350), back in the day (maybe 6 or 7 years ago) and can even remember having the same problem. I remember that there was something with "some HEI" modules that prevents it from starting. After doing some digging I'm thinking that it's the "apply 5v reference signal during cranking discussed here:
http://www.diyautotune.com/tech_arti...part2-nova.htm

I think that in my formula I did it in the wiring harness (I don't really remember), but since there is a mod kit out there that just adds 2 jumpers and a resistor I decided to just do that the other night.

After that I tried it again, no better. It cranks, but no start. Doesn't even act like it's trying to start. With TunerStudio hooked up and he dash up I get sensor feedback (like the CTS and TPS are working), but when I turn the key no Tach, and nothing from things that I'm assuming need to see a signal to happen (like no injector pulse width).

I plugged the stock ecm in and it fires and runs fine (so I know that I didn't hurt something like the HEI module or something), and I pulled the MS to GM harness adapter and got continuity between the HEI pins on both sides so I know that the signal is getting through the adapter.

I hooked up the STIM to the MS to make sure I didn't mess something up doing the HEI mod (since I knew that this setup worked before on my '98 Formula), and that works fine too, I can change the rpm pot and I see it on the dashboard

I'm at a loss what else it could be/what else to check. I suppose it might be my .msq, but I would think that even if my settings were completely wrong (which is a possibility, the TunerStudio settings are different now than when the instructions were written), I would imagine I would at least see a cranking rpm when cranking the engine if it sees the rpm with the STIM connected.

Six_Shooter

iTrader: (2)

It sounds like you need to find why you're not getting a signal or strong enough signal from the HEI module to the MS.

Do you have or have access to an oscilloscope?

JP86SS

iTrader: (1)

The pickup coil wires could be reversed.
Something happened a while ago to me and that turned out to be the cause.
I didn't think it could be a problem being like that but I flopped them and it worked.
Might want to see if the MS has it different than the GM.
Does sound like its something with the ign signal.
Is the MS unit looking for module output (sq 5V) or input (sine, zero crossing)?
Something to check anyway.
Jp
Link to some RBob wisdom on the subject.
https://www.thirdgen.org/forums/diy-...out-spark.html

willexoIX

Correct me if im wrong, but the 5v ref isnt supposed to be there during cranking, only run if im not mistaken. At least thats what I remember from installing my Megasquirt. Mine is an MS1/extra.

LilSki

iTrader: (1)

5vref is there during cranking. If you don't want to to be you need to run it through a relay that only trips when the key is in run and not start. That is how I have mine set so it starts on base time.

83 Crossfire TA

iTrader: (2)

FWIW, it was the cranking timing bypass which is listed as a problem with _some_ aftermarket HEI modules... BS, I've seen it with 2 original OEM modules now... fixed by adding power only while cranking to pin C9 on the adapter.

willexoIX

Mine starts on base time without the relay. No 5vref while cranking. Once running the MS sees the 5v and takes control of timing. On mine anyway.

LilSki

iTrader: (1)

Oh maybe the later firmwares don't send 5vref on crank. When I was using B&G code it was there and definitely caused some abnormal timing during cranking. Back then I installed a relay but haven't checked it since I went to MSextra.

willexoIX

As a matter of fact I think you are correct, though I never ran the B&G firmware I remember reading that was one of the changes when switching to MSextra.

gp90gta

iTrader: (1)

Is this a diy pnp? Which module, hei7 hei8?, how did you build the circuit for ignition?

willexoIX

Www.diyautotune.com

Www.msextra.com

Two of the sites having to do with megasquirt.

Take a gander at "another turbo 2.8 in progress" over on the v6 section of this site, I documented alot of my MS build in there with pics and links.