skipperHVAC

Hello there all,
I’m new to post but have been lurking a while. I’ve been fishing through posts for info on the Mefi 3 Ecm’s.

I could really use some help from anyone ho has been tuning these boxes. I have purchased MEFIBURN and have no problems with the uploading, however I am lost in 1 dilemma.

I have dropped a 98 454 MPI motor in 89 Bayliner 2850, Errrrr I know but I have a Baja also with a great Gen V edelbrock heads, roller and all the rest t, I built 2 years ago.
But on the bayliner I left in the OMC anchor, oops, I mean drive and the shift interrupt is driving me nuts.

Ok most know an OMC Cobra will not come out of any gear forward or reverse without a momentary engine stall, you can pull on the shift handle all day until you rip the cable out of the gimbal. If the motor does not drop the rpm down to about 250 300 for a second your hitting the dock.

I have spoken Bob to a few times at, OBD Diagnostics and he said he has not had anyone really use the interrupt. The software has the flag switches to enable the shift interrupt but seems to only drop the rpm by about 40 or 50. There is a shift interrupt kill mode also and when enabled, does its job, a momentary blip and the motor dies. I built a relay with a lag and and other gizmos to make it open and close about 1 time per second, BTW that’s what I used for an interrupter with the old OMC setup, because I kept blowing the OMC module.

I tried to interrupt the coil with this relay, and the Ecm sees the no rpm for a second and thinks its restarting each time the interrupt is done, and the Rpm’s flare, and the Iac starts to open, but most of the time it will stall anyway.

If anyone has an idea as to what I can change to make the motor cough for a second I could really use the info.
BTW, I had to swap pin 20 for 9 on the Mefi3’s J2 connector, because I’m not using the shift anticipation and pin 9 is for the interrupt, However I an using the connector that was on the harness with the jump loop.

I really prefer to do it through the Ecm, and I figure if there is a setting for the shift interrupt, it should be able to actually do more than 50 rpm drop I am getting out of it. I think the ecm catches the motor going to stall and corrects it, but I have no idea of what else to change to stop that. Please help after 5, 460 motors I found a sweet 98 454, with all the trimmings, rebuilt it added a few ponies and it runs great, I know I should have used the Bravo with it, but didn’t have the time to hunt down the parts.
Bob,

NordicSS

Hook it up like a alpha and ground the coil out when pulling out of gear.

skipperHVAC

Thanks for the info but as mentioned above, the Ecm sees that as a restart and the rpms flare to about 900 then come back down. And most of the time the motor will die.

Traveler

I run accel DFI on an alpha drive and had the same problem. The coil thing didn't work for me either, the engiine would stall. What I did was wire the shift interupt switch into the ESC line. The switch is normally closed. When you go to shift it opens which causes the timing to go to the distributor base setting. The distributor is set to 10 degrees but I run around 25 at idle on the computer. Pulling the timing slows the RPM and I can shift.

btribut

I have a mefi-3 in a mercruiser 4.3 TBI. Engine was a bravo application that we are converting work with Alpha. I think we have gotten past the shift interupt issue however under load the engine stays at base timing. Why would this happen?

FIXX

iTrader: (2)

put a resister in line on the - side wire coming from the ecm to the coil.you can get them at radio shack. the ones i use are about 1/4 '' in diameter solid wire,black with a silver stripe..silver stripe going in line towards the coil..it will let the - signal pass through but wont let the - signal spike back to the pcm..

just something to try..

their may be another way to brake the signal with a relay..with the relay you will have to cut the - wire going to the coil, hook # 30 on the relay to the - wire coming from the pcm, hook 87a to the cut - wire going to the coil,hook 85 to a + ignition source and hook 86 to your shift interrupt switch 87 wont be used..this will momentarily brake the connection at the - side of the coil..