MX-5 1990/93 Megasquirt start up issues

[DanM]

So I'm moving this discussion from my build thread to tech talk to help anyone who may experience similar issues in the future.

 

Background

I am using Megasquirt MSPNP2 as my chosen ECU for my 1990/93 1.6 MX-5 engine.  The engine is basically stock, but I have removed the Air Flow Meter and replaced with an Intake Air Temperature Sensor (IAT) and installed an Innovate MTX-L O2 sensor (wideband).

 

I have loaded the base ECU map for 9093 mx-5 and adjusted the configuration for the IAT and O2 (basic drop down settings).

 

Problem

The engine will crank over but will not fire up on the base map (and it should).

 

Checks

I have the following data from the checks that I have performed.

 

• Fuel Pump - Working
• Intake - Clear
• Spark - Confirmed
• Battery - Delivering >12V
• Starter - Working
• Injector harness - Noid light test fail (12V Confirmed but no signal ground)
• ECU tuner shows RPM
• ECU tuner shows AFR (O2 sensor)
• ECU tuner not showing Throttle position (not sure if it supposed to)
• Engine light remains on when keyed to "On" position

 

Why is the ECU is not sending signal ground to the injector?  Any ideas for the pot?

[fastg]

Well you need to start with the harness, which one did you use, or was it an adapter? But start there follow the ground wires back from the injector all the way to the ECU. Megasquirt's on a Miata are very ground sensitive, did you use the correct ECU to engine ground? There might be something in the install notes, about grounds, if there is follow them to the letter. 

 

There is an amazing amount of support for the MS on https://www.miataturbo.net/megasquirt-18/ almost 650 threads, they have been involved with the MS since the early days. There used to be a user Brainiac or something like that, he built 100's. Including mine. 

 

Graham 

[DanM]

I cranked it over and checked the timing last night and the timing is exactly where it should be, 10 degrees retarded Advanced.

 

Edited August 20, 2023 by DanM

[fastg]

"10 degrees retarded" from what, 10 degrees ATDC (After Top Dead Center)  will not work, you always need some advance to run, 10 degrees advance is a good status fixed timing starting point. 

 

https://www.diyautotune.com/support/tech/other/base-timing/

 

But I thought we were thinking it was an injector problem, what changed?

 

Graham 

Edited August 19, 2023 by fastg

[DanM]

Yeah, sorry Graham, I was very tired when I wrote that.  It is 10 degrees btdc.  I've updated it now.  I'm taking input from multiple forums right now, just trying to gather as much data as I can to narrow down the problem.

Edited August 20, 2023 by DanM