08-07-2014, 07:21 PM
Join Date: Nov 2011
Total Cats: 0
Car won't start, intermittent spark
My car stopped running a couple weeks ago at the track and I'm looking for some help in troubleshooting. The engine stopped running after a downshift before I got back on the power in a corner. I was able to coast into the pits, but ever since then the car refuses to start. The engine turns over and I've checked many things with no results. When the engine cranks it occasionally sputters lightly as if it's trying to fire, but never makes much progress. I'm a bit of a useless noob when it comes to my megasquirt, but I did run a few ignition logs and got inconsistent info. The latest ignition log after all the troubleshooting described below seems to imply that the ECU is getting a good CAS signal.
Background info: My car is a 1995 with a Flyin Miata turbo kit and Reverant Enhanced MS2 ECU. The car has been turbo'd for over a year with over 15 track days and was running strong right until it died.
To date I have done the following to try and fix the problem:
- Checked fuel pump, it runs as expected and fuel can be smelled in garage after cranking
- Listened to injectors with stethoscope and can hear them firing
- Checked throttle body and throttle cable, they are not stuck
- Checked spark with timing light (on all spark wires), spark is intermittent and inconsistent
- Checked spark by pulling plugs out and cranking engine with plug resting on engine: spark is intermittent and inconsistent
- Changed plugs (to recommended NGK plugs that were properly gapped)
- Changed ignition coil
- Changed Main relay
- Changed Camshaft Angle Sensor
- Checked CAS wiring (has ground continuity, 12 volt, +4V, -4V when in run)
- Visually inspected grounds and ensured they were tight (strap near dipstick, grounds under master cylinder, ground at back of intake, ground at front of intake)
- Wiggled the CAS/Ignition coil wiring during cranking, no effect
- Checked that it has oil
- Verified oil pressure during cranking
- Verified timing belt is in one piece (through hole left during coolant reroute, I did NOT remove belt cover to verify timing, however timing belt was changed 2 years ago prior to turbo, and was re-verified when engine was out to fix oil pan leak and do coolant re-route 1.5 years ago)
- Verified cams turn when cranking (through oil filler port)
Right now I'm thinking there is a shorted or broken wire somewhere (in the engine bay or at the ECU), that I have a bad ground, or something has gone wrong with the ECU. Does anyone have any tips on where to look for said items? Or if there are other possibilities for why my car won't start?
The wiring diagram implies that there is a ground on the top of the engine, but i'm not sure where that is. Does anyone know? Also, is there a good method for getting good grounds beyond cleaning off the terminal and tightening the bolt well?
Also, I have a data log and ignition log that I took today while cranking the engine. I attached them so that you could look at those and let me know if I'm missing some key info that's in there.
Thanks in advance for any help,