N3v

ok, so I'm helping someone megasquirt their 1990 right now, and I've gotten to a point where I'm kinda stumped. When the key is in the ready position everything seems good, but when you try to crank it, the megasquirt turns off. I've megasquirted two 1997's, but I just don't know the wiring on a 1990 as well, and the wiring diagrams in cjernigan's sig aren't working anymore. I wired everything up per braineack's thread.

when the key is in the 'ready' position:
- all the gauges read like they should
- car does that little backfire fart thing, which is good cause it shows the ignition is hooked up
- no voltage on the grey +5v Vref wire (problem?)
- battery voltage shows across the main red positive wire for the megasquirt

Then yeah, when I cranked it the megasquirt turned off, then wouldn't turn back on. I pulled it out of the car and hooked it up to my stim and it operated normally. It's running ms-extra code. Am I missing some wire? what wire on the plug is the dedicated voltage line for when the car is cranking? Are any of those wires supposed to lose power when the car is cranking? Thanks.

Joe Perez

iTrader: (8)

The white/red wire at position 1B is the primary ECU power line form the main relay. It is hot in both Run and Start.

Have you measured the ECU power line during cranking to see if any voltage is getting there?

N3v

thanks for the input joe. here's some further developments.

megasquirt responds fine on the stimulator, but when i plug it into the car, the megasquirt turns on and off in a split second. the car sometimes farts/backfires when this happens. it's running 440ccc injectors so thats probably why that is happening, due to a fuel leak or something. anyway, there is no voltage across the grey +5v vref wire when the car is in the ready position, no matter if the megasquirt is plugged in or not. the main power line (white/red 1B) stays hot during the ready position and while cranking. I checked all fuses under the hood, nothing is blown.

thoughts? oh btw, this can't be a problem yet, but I just loaded an msq to the 1990 from my 1.8 to set up most of the settings like they should be. do I need to change anything in the msq for a 1.6?

N3v

ok, new development. I thought it wasn't booting, but it was just taking a really long time to boot. the two ignition LEDs on the MS start really really dim, then get brighter, and finally the middle light kicks on and the car afterfires. I'd say it takes a full 15 seconds. It boots immediately on the stim though, so I don't think its a faulty component on the megasquirt itself. Also, I've cranked it when it took 15 seconds to boot and the megasquirt stayed on, but I got no tach reading. I'm using a known working msq from my 1997 1.8l

DMRider_10

Dont use the .msq from your 1.8, use the PNP 1.6 map with the req fuel and cranking PW adjusted for your injectors

N3v

this car has 440cc low impedence supra injectors on it, and resistors were installed to effectively make the injectors high impedence to run on the stock ecu. When the key is turned to the ready position, the two outside LED's on the megasquirt start out very dim, and they brighten very slowly and flicker, every time they flicker the injectors click. then eventually they brighten up to regular brightness and the middle LED turns on and the spark plugs all fire once because the megasquirt actually booted.

So anyway, I figured it might be the resistors in the injectors causing the problem because the injectors were clicking, but we removed them and the problem was still there.

N3v

also I didn't ground all the wires like joe prefers, I just grounded six of them like in braineack's diagram

DMRider_10

same as most people i would have thought

Braineack

iTrader: (62)

unplug your injectors, does it start up instantly?

N3v

ok i got it running. it was a grounding issue. the only wiring I didn't do myself. Anyway, now that its running its having a problem, but I feel like its more common. it runs into a wall when you rev it to around 3k or when the turbo (2556) would probably spool. its like a rev limiter. I have a log of the occurance. you can rev it to like 3500rpms if you baaarely give it gas, but thats about as high as it can go.

Braineack

iTrader: (62)

hard to guess without an o2 reading or an attached msq. just going to throw over boost protection out there....

DMRider_10

Sounds exactly like overboost protection^

N3v

nope, that was the first thing I checked. This car doesn't have a wideband in it yet, it's still in the mail. I'm just trying to knock out all of the underlying issues before the actual tuning comes into play. To see if it was the tune causing it to happen, I changed the fuel map between 50% and 150% of the base map, and it still cut in the same place. I've never tuned a boosted car though, so I could very easily be missing something.

The megasquirt has no mods on it right now, besides an idle mod. The car has a manual boost controller. It is running 440cc low impedence supra injectors with resistor packs installed on them, which makes them the same resistance as stock miata injectors, apparently. It also has a fuel pressure regulator. Adjusting the fuel pressure didn't change anything.