Died twice under braking, won't crank a few days after
#1
Moderator
![](/mt2011/images_td/ranks/supporter1.gif)
![](/mt2011/images_td/ranks/moderator.png)
Thread Starter
iTrader: (12)
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,885
Total Cats: 3,075
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
My engine quit, tach immediately to zero, on the interstate offramp. I dropped the clutch and it refired. Then I attempted to brake again and the tach dropped immediately again. The car still had momentum so I dropped the clutch and it refired again. I drove around for a while longer trying to get it to die again but it didn't.
I pulled the seats out and replaced the carpet and harnesses.
Now the car cranks but doesn't fire. I don't hear the fuel pump cycling. And the laptop suddenly doesn't connect to the MS3 Basic so I can't composite log. I tried jumping the FP to GND in the diag box and the fuel pump is still quiet.
Is the inability to connect the laptop to the ECU a red herring? I'll check the FP relay tomorrow and the pump itself. Any other ideas?
I pulled the seats out and replaced the carpet and harnesses.
Now the car cranks but doesn't fire. I don't hear the fuel pump cycling. And the laptop suddenly doesn't connect to the MS3 Basic so I can't composite log. I tried jumping the FP to GND in the diag box and the fuel pump is still quiet.
Is the inability to connect the laptop to the ECU a red herring? I'll check the FP relay tomorrow and the pump itself. Any other ideas?
#5
Moderator
![](/mt2011/images_td/ranks/supporter1.gif)
![](/mt2011/images_td/ranks/moderator.png)
Thread Starter
iTrader: (12)
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,885
Total Cats: 3,075
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
I haven't checked the spark but doesn't have tach or FP. I'm frustrated with the not connecting. Would main relay do that also?
Opened the MS3 Basic and I see both the 12v and 5v LEDs lighting up
Opened the MS3 Basic and I see both the 12v and 5v LEDs lighting up
#7
Tweaking Enginerd
![](/mt2011/images_td/ranks/supporter1.gif)
iTrader: (2)
Join Date: Mar 2013
Location: Boulder, CO
Posts: 1,809
Total Cats: 366
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Edit: yes on the main relay for tach and fp
#9
Moderator
![](/mt2011/images_td/ranks/supporter1.gif)
![](/mt2011/images_td/ranks/moderator.png)
Thread Starter
iTrader: (12)
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,885
Total Cats: 3,075
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
I upgraded my mechanical boost gauge yesterday and had to wire up day/night color change plus 12v acc power also. It works but maybe something popped on one of the other circuits under the dash due to my activity.
I'll pull and inspect all of the fuses in the driver's kick panel before proceeding. If the room fuse feeds the ECU that will be something to check.
Then I'll proceed to injector harness wht/red.
I'll pull and inspect all of the fuses in the driver's kick panel before proceeding. If the room fuse feeds the ECU that will be something to check.
Then I'll proceed to injector harness wht/red.
#10
Moderator
![](/mt2011/images_td/ranks/supporter1.gif)
![](/mt2011/images_td/ranks/moderator.png)
Thread Starter
iTrader: (12)
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,885
Total Cats: 3,075
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Injector harness wht/red has 12v positive when key on, so main relay is operating.
Room fuze is good. Also meter and engine fuses on same interior fuse panel. All of the fuses there are good.
I wish the megasquirt would connect so I could get a composite log.
I don't know what to check next.
Room fuze is good. Also meter and engine fuses on same interior fuse panel. All of the fuses there are good.
I wish the megasquirt would connect so I could get a composite log.
I don't know what to check next.
#14
Moderator
![](/mt2011/images_td/ranks/supporter1.gif)
![](/mt2011/images_td/ranks/moderator.png)
Thread Starter
iTrader: (12)
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,885
Total Cats: 3,075
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
I'm trying to connect with a different laptop right now but it's old and I'm having to update and reload some programs. I'm trying the old laptop because it has a real serial port.
I've got a multimeter. Somebody come up with the bright idea of what I should check, LOL. I'm baffled unless the 'squirt got popped. But then the FP should still make noise when jumped at the diag box.
I've got a multimeter. Somebody come up with the bright idea of what I should check, LOL. I'm baffled unless the 'squirt got popped. But then the FP should still make noise when jumped at the diag box.
#15
Moderator
![](/mt2011/images_td/ranks/supporter1.gif)
![](/mt2011/images_td/ranks/moderator.png)
Thread Starter
iTrader: (12)
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,885
Total Cats: 3,075
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Okay tried an actual jumper wire instead of the staple I was using previously for the fuel pump to ground and
EDIT something weird happened
EDIT something weird happened
Last edited by sixshooter; 05-03-2020 at 12:37 PM.
#18
Moderator
![](/mt2011/images_td/ranks/supporter1.gif)
![](/mt2011/images_td/ranks/moderator.png)
Thread Starter
iTrader: (12)
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,885
Total Cats: 3,075
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Ok. Fuel pump relay buzzes when the FP to GND is jumped in the diag box and the key is turned on. If I disconnect the MS it doesn't buzz. The FP can't be heard either way.
I'm suspicious the MS fuel pump circuit is fucked, otherwise this buzzing wouldn't occur from jumping in the diag box.
I'm suspicious the MS fuel pump circuit is fucked, otherwise this buzzing wouldn't occur from jumping in the diag box.
#19
Moderator
![](/mt2011/images_td/ranks/supporter1.gif)
![](/mt2011/images_td/ranks/moderator.png)
Thread Starter
iTrader: (12)
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,885
Total Cats: 3,075
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Disconnected harness from fuel pump relay and checked with a multimeter. Both White wires with red stripe do not have 12 volt positive with key switch on.
This leads me back to the main relay or some portion of the harness. I don't understand why I had good 12 volts on the injection harness earlier. Going to recheck that and make sure that has not been lost.
This leads me back to the main relay or some portion of the harness. I don't understand why I had good 12 volts on the injection harness earlier. Going to recheck that and make sure that has not been lost.