Died twice under braking, won't crank a few days after
 

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?

Any spark? That'll at least rule out the trigger wheels/CAS/.

Year?

Main relay could.do everything you describe.

96

No tach movement when cranking, btw.

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

Confirm you have 12V on any one of the wht/red connections KOEO.


https://cimg4.ibsrv.net/gimg/www.mia...816c026de4.jpg

i am not familiar enough with the Basic or the 96, but it looks to me like the room fuse supplies 12V to the MS at all times. There may be a back drive, or the bridge chip could be powered from the R/W

Edit: yes on the main relay for tach and fp

When did this happen?

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.

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.

If the Megasquirt has 12v and ground, you should connect. If it's not, diag that, ending with pulling the case off and checking for burnt traces.

In addition to Curly, something else isn't adding up. If you have W/R 12V, the FP should turn on with the diag port short.

https://cimg4.ibsrv.net/gimg/www.mia...d01789b820.jpg

Would that mean that not being able to connect is a red herring and I might have a fuel pump relay or fuel pump problem?

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.

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

you idiot, you used the wrong office supply to jump the FP. Everyone knows the proper tool is a paper clip, not a staple dummy.

Something under the dash is buzzing with it jumpered. Trying to take - apart to investigate

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.

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.

12v+ has been lost at injector harness. I must have popped a fuse somewhere or have a bad connection.