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I'd sure appreciate some help with a sudden no-start situation. I started my car for my weekly trip to Cars & Coffee but the engine died after a few seconds. The engine cranked when I tried restarting but nothing else happened. I'm seeing AFRs of 22.4 after cranking, which lead me to wonder if there's a fuel issue. I put the MS into test mode and verified I could hear both the ignition system and injectors firing. I also put the fuel pump into test mode and it sounded like fuel was flowing. I see a signal from the CAS so it seems that should be OK. The main relay appears OK because I'm still able to communicate with the Megasquirt. I swapped it out for another one just to be sure but had the same problem.
I can't think of what else could be causing this. Would you please look over my log and tune files to see if anything pops out?
to confirm, you are seeing rpm signal when cranking? Can you confirm that the injectors and ignition are working during cranking? You do have gas, right?
I can see the tach needle move when cranking and I can see data on the RPM trace in MLV. I'm not sure how to confirm that injectors and ignition are working while cranking but I hear them working when I'm in test mode. Yes, there's sufficient fuel in the tank and I verified that auxiliary fuse and relay I installed for my fuel pump are good.
I looked a little closer and it sounded like fuel wasn't actually flowing after a few seconds. I checked for power at the fuel pump and saw correct voltage for a few seconds after turning the key to On, which seems to be the priming behavior. After that the voltage drops to zero.
That would sure explain the apparent no-fuel behavior. Any ideas why there would be power to the fuel pump during priming and then nothing? Could the fuel pump relay be acting up?
Last edited by aceswerling; 08-26-2017 at 04:47 PM.
It is normal FP operation by MegaSquirt to run the pump 1-2 seconds with KeyOn. The MS turns it off until there is an RPM signal. So, pump should come back on when actually cranking.
Look for voltage to pump during cranking. If you have it, then that is not your issue.
OK, that's good to know. I'm seeing ~11.5v at the plug when the car is cranking so there's power after all. I'll look at the pump and wiring next. Thanks for the pointer.
Sure, here you go.Thanks very much taking a look, Aidan.
As an update, I pulled the fuel pump and verified it's running properly as DNMakinson described. I applied some power outside the car and also saw it run when connected to the car. Seems like the fuel pump isn't the issue.
How strange. I clicked the link from within the forum and Excel opened it for me. I've saved the data in an Excel XLS format with the hope that'll be better. Can you try this version?
Ah, OK. I don't know what's causing that problem so I took another log and verified that MLV would open it. I'm also posting 2 screenshots in case there's more trouble.
Trying to think what else could be going on. Is it possible the fuel pump isn't actually pushing fuel even though the motor is running? Very little fuel came out of the lines when I disconnected them from the pump. It was much less than I'd seen before and more of a dribble than a pressurized squirt. That makes me wonder if the pump is making pressure. Has anybody seen this failure mode on a DW200 pump?
i would suggest pulling a couple of plugs to see if they are wet or dry. that will be a good indication of if it is spraying fuel or not. while it is out you can also test that the spark is working as it should. When trying to start, do you get ANY kind of response from the engine as if it were trying to start?
Thank you for the suggestion. I went through everything again today, starting with verifying if I had fuel pressure. That was OK so next I used test mode to validate again that the fuel pump, ignition, and injectors were working properly. They all seemed fine so I moved to your suggestion to see if the plugs were wet after cranking. It turns out they weren't so I knew there was a fuel issue. Didn't know what it could be. As a hail Mary play, I decided to revert to a previous version of the tune. I hadn't changed anything that should have made a difference but I thought it was worth a shot. The car started right up on that old tune. Go figure.
So thankfully, everything is working fine, even if I don't know why. I've uploaded the tune that's working now in case anybody wants to take a look.
And your good disposition gets you back to equilibrium on Cats.
EDIT: I loaded your tune and then did a compare to the other tune. Not much difference between them, and not enough to make the car not start, that I could see.
Wonder if you just needed to restore. I'm interested to know what would happen if you put the other tune back in.
DNM
Last edited by DNMakinson; 08-29-2017 at 08:19 PM.
Thank you very much for the cat. I've always endeavored to be a valuable member of this community and deeply appreciate the encouragement. It's taken effort to learn how the Megasquirt operates and to work through some oddities of my installation. I couldn't have learned without this forum and I'm profoundly grateful for the information and guidance I've been given. I offer my thanks to all of you.
FWIW, I tried the non-functioning tune again and found the engine wouldn't start, even after bopping back and forth a few times. Perhaps it's corrupt in some way?
Any errors when you load it? The only differences I saw were Overboost tolerance was turned on. Maybe its because your boost target is 0 down low its turning on overboost?
Try turning off boost tolerance. Its in the boost control settings menu.
Thanks, Aidan. That did the trick. Still, it's interesting the car would start at all with these settings. I turned on Boost Tolerance about 2-3 days before the no start condition showed up.
In any case, is Boost Tolerance a good feature to enable? I recall my boost control mirrors settings you posted so perhaps it's not needed. But assuming you're correct and that we decide it's a good feature to use, then changing the bottom row of the boost target table to something like 100 should allow boost tolerance to work, right?
BTW, many thanks for the boost control settings. It's made my car much more enjoyable to drive now that I can control the power. It's much less wild and (frankly) dangerous now.
08-26-2017, 01:11 PM
MS3 Won't Start
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