No start SR20DET with fuel and spark [SOLVED]

[boosted240]

(see last post for short synopsis of issue and fix)

Hello all,

Engine was running good on E85 after a fresh build. I had more than desired valve noise so I recently re-shimmed my SR. Engine was down about 4 months during this period (got married an stuff which caused delays). For those who aren't familiar, only the cams are needing to be removed for adjusting the valve height. I put the engine back together and had a no start situation. I double and triple checked my timing and took pictures as well to show, but apparently can't upload them regardless of the file size. Please verify yourself in case I'm missing something. During my troubleshooting I found that I didn't have spark or fuel. I then checked the ECM tach pulse LED on the side of the module, it wasn't flashing however I did see RPM value on the log file. I then supplied 12V directly from battery to ECM pins 38/47 as they weren't getting any voltage (I don't know why yet). Once I provided 12V to those pins the tach pulse LED began to blink while cranking and I now had fuel (verified by pulling the fuel rail off the intake, all injectors firing) and spark (verified by pulling all coils to test with spark plug). So now I have a once running nicely engine with a no start condition with air (compression), fuel and fire. When I say no start, there's really not even an attempt. On occasion the starter will get "hung up" which is normally associated with "starter kick back" when timing is off, but I don't think that's the case here.

ECM info:
- MSPNP2
- Firmware: 3.0.22

Things I've considered:
1. I have tried switching the ignition coils around in case my timing was off by 180*. No impact.
2. Had the battery tested by two different stores, 710CCA @ 12.5V. No issues.
3. Tried a different battery as well as two batteries in series for more power. No impact.
3. Tried to get some fire going with starter fluid. No impact surprisingly.
4. Reflashed the ECM with a few different calibrations and then back to the last known good cal. No impact.
5. Adjusted cam angle sensor (CAS) both retarded and advanced. No impact.
6. Added 100% additional fuel during cranking. No impact.

[jsmcortina]

In both logs, the ECU thinks it is operating the injectors and wasted-spark coils.

Your battery voltage does get very low during cranking though (down to 6V.)

Back to basics:
- are the spark plugs wet or dry?
- leave the plugs out of the next test
- remove power from the fuel pump and check that the coils firing at the correct time - check timing with a strobe during cranking on each plug lead.
- also test the coils using the spark test mode

James

[boosted240]

---Partially solved---

OK I did some homework and found that the global timing, "Trigger wheel tooth #1", needed to be change from 78* to 121* BTDC, 43* difference. Geometrically this really doesn't make any sense!??!!! I found this by checking the timing when the crank timing was set to 0* with the plugs out to ensure good engine speed. This absolutely baffled me because the mechanical timing between the CAS, crank and cams were all correct. This doesn't make sense to me. The engine seems to run fine stationery in the garage, haven't driven it yet. I'm starting to think that something has changed with the ECU. Penny for your thoughts?

I also checked the resistance and voltage drop from the +V on the battery to the alternator and the underhood-fuse box to see if there were issues with my wiring. Resistance from the battery (which is in the trunk) to fuse box and alternator was .01 ohm with 0V loss. No issues there, but can't explain the low battery voltage during crank.

Still can't get tach pulse without supplying 12V to pins 38/47. Haven't investigated fully yet to be fair. I'll have to try to find the appropriate schematics to troubleshoot whether it's an ECM issue or a relay issue. I'm guessing that it's an ECM issue since nothing else on the car has changed since the valve overhaul. I hope I'm wrong though... to be continued.

[boosted240]

<<SOLVED>>

Pin 4 should've been pulled low instead of +12V at key on which then provides the low side to activate the ECU relay which supply 12V to pins 38/47. In speaking with Megasquirt technical folks I quickly found out that there's a known issue with the MSPNP2. I sent the ECU back to MS and they repaired it at no cost except for shipping one way. Based on the notes they left on the ECU it appears they had to replace a capacitor, resistor and a diode.

Thanks MS for standing behind your product.

[eekoog]

Hi,
It is a bit of a long shot but i am having the same issue with the "ECU relay" on pin 4 that doesn't turn ON.
Do you know why pin 4 stays at 12v instead of ground ?
This is on a customer's car so i cannot wait to send the ECU back to DIYAutotune. I have to solve it myself. No issues with soldering.

Thank you.

[jsmcortina]

Probably best to start your own topic rather than tailing on to a 7 year old one.

James