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Shift interrupt on a Bravo engine MEFI-3

4K views 9 replies 5 participants last post by  Traveler 
#1 ·
Hello
I am new to this forum here.
I bought a 6.2 MX MPI from 2001 for in my 19ft Monterey to use it with my existing alpha drive.
The engine uses a MEFI-3 controller and is wired for a shift intrrupt switch. When monitoring wit a DDT or scantool I can see the status for interrupt changing from off to on. But it has no effect on the engine. It looks like the shift interrupt part of the software is missing.
So I need a solution for this, reprogramming or alternative.
I am also in contact with Mark from precision and Tyler crockett, but no solution so far.
And I can use an extra ECU, anyone one left?

Richard
 
#3 ·
Not sure what the issue is with your setup but this may be helpful. My setup is an alpha drive with Accel DFI fuel injection. To get the drop in RPM the drive needs to shift I wired the shift interuptor into the "Timing" signal between the computer and the distributor. In case I don't have the right name, it's the cable you disconnect to set base timing. In my setup the shift interupter is a normally closed switch. When you go to shift the switch opens and the distributor defaults to base timing which in my case I've set to about 4 deg BTDC. While you probably can't adjust youre base timing, if you get the same drop in RPM when the distribuotr goes to base timing it should work. If you know enough to call a meter a DMM you should be able to figure out the wiring. Hope this helps, good luck.
 
#4 ·
The ALPHA drive shift interupter was a normally open switch that when you tried to shift the resistance would close the switch and cause a temporary short to ground of the signal side of the ignition coil and this would stop the spark just long enough to cause the engine to stumble and the drive to come out of gear.
The shift interupt ONLY works to get out of gear.
 
#5 ·
Sorry to disagree but your information is not true in all cases. On a 1998 MEFI 2 the switch is noramlly closed and it does not go to the ignition coil even though the schematics say so. It's in fact a NC switch wired directly to the ECU as a digital input.

I painfully chased a stumble for an entire summer, in the end to discover an intermittent switch that was dropping ignition. (Lots of new EFI parts for sale if anyone's interested :))
 
#7 ·
That is correct,
The engine uses a MEFI3 ad there is a input for the interrupt. With a scantool or DDT you can see the setting change from off to on. But since this engine is only sold with a bravo there is no provision in the software to "do" anything. So I need an alternative maybe cutting the injector feed? Anyone tried a programmable ECU from AZ?

Richard
 
#8 ·
Change the switch to the older open type and if this engine has a coil just ground one side of the switch and run the other side to the signal side of the coil.
When the switch trips it will ground out the coil and kill the spark for a second. This will work as long as the coil is fed with 12 VDC on the hot side.
 
#9 ·
I still haven't found a solution for it. I spoke to Mark from precisionmarine and should be able to do the remap.
But I like to keep my current ECM at home so I need a spare one.
Does anyone know a good source for a MEFI-3 ECM?

What about the idea of cutting/interrupt the power feed for 4 of the 8 injectors?

Richard
 
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