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Old 05-11-2005, 11:30 AM
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Default EFI Gurus wanted

How do I hook up the shift interupt switch???? I am repowering my 93 boat with a 95 350 MAG MPI (engine only)The problem I have is that the boat has an Alpha and the 350 MAG is from a Bravo package.

Has anyone done this before? Is it as simple as splicing the white wire at the Dist. to the shift interupt switch or do I need to change to the original 350MAG MPI Alpha harness and ECU?

Thanks for any help.
wally.
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Old 05-11-2005, 12:21 PM
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Default Re: EFI Gurus wanted

You pretty much have it figured out. You will need a normally closed shift interrupt switch (opens when activated) wired into, as you mentioned, the IC circuit (white wire at dist). This is assuming you are using the Delco EST distributor.

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Old 05-12-2005, 05:15 PM
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Default Re: EFI Gurus wanted

I treid the white wire with no luck. The issue is that the shift interupt is contlolled by the ECU and this ECU is for a Bravo and doesn't have the program for shift interupt.

Does anyone know of another way to hookup the interupt switch. I also tried hookig it up to the lanyard circ but it killed it instantly.

Help
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Old 05-12-2005, 08:07 PM
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Default Re: EFI Gurus wanted

I hate to tell you this, but you need the Alpha ECU
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Old 05-12-2005, 11:56 PM
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Default Re: EFI Gurus wanted

You don't need a different ECM.

You do have a Delco EST Distributor, correct?

Assuming this is the case, I think you are using the wrong interrupt switch. Are you sure you are using a normally closed interrupt switch? The normally open switch is much more common. If you are using the wrong switch, the engine will start and run, but the interrupt switch will have no effect.

Using the wrong switch will set a trouble code 42, if you have a scan tool to check that.

If not, test the switch for continuity when it is not activated (not depressed) with a mutlimeter. Or, you can test the wiring and switch by depressing the switch, holding it down while starting the engine (you may need a helper to do this), then releasing the switch. If the engine dies, your wiring is correct, but you have the wrong switch.

Dave
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Old 05-16-2005, 12:18 PM
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Default Re: EFI Gurus wanted

Dave,

My dist has two plug-ins at the base, one is a 4 wire that goes to the ecu and the other is a 3 wire the goes to the coil. The switch I am using came with the new shift plate kit, Merc# 864363A 1. I never tried it with the old swicth. Even with the engine running when I removed the white wire from the dist it kept running.

I hope I am doing something wrong cause the only other option might be what Marc from BAM said, that I need the Alpha ECU, and if so, anybody know where I might look for a used one?

Thanks for your patience and you help. If it would be easier you can call me toll free @ 1-888-310-0222 pacific time.

Thanks again,
Paul.
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Old 05-16-2005, 12:40 PM
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Default Re: EFI Gurus wanted

Originally Posted by Dave_N
you can test the wiring and switch by depressing the switch, holding it down while starting the engine (you may need a helper to do this), then releasing the switch. If the engine dies, your wiring is correct, but you have the wrong switch.
Did you do this test?

Dave
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Old 05-16-2005, 02:00 PM
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Default Re: EFI Gurus wanted

No not yet. But I thought that disconnecting the white wire at the dist shoulddo the same thing as the switch, kill the motor, & it didn't.
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Old 05-16-2005, 03:32 PM
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Default Re: EFI Gurus wanted

The reason it's not stalling when you disconnect the white wire at the distibutor, is due to using the wrong (normally open) interrupt switch.

To explain;
When when you start the engine under normal operation (IC circuit closed) the ECM immediately switchs from "Distributor Module Mode" (using the timing signal generated by the ignition module) to "Run Mode" (using the signal generated by the ECM, using the IC circuit to send the signal back to the ignition module). In Run Mode, interrupting the IC circuit will stall the engine.

What is happening is that when you start the engine the ECM is detecting an open IC circuit (due to the normally open instead of normally closed shift interrpt switch), and is not switching to Run Mode, instead staying in Distributor Module Mode.

In Distributor Module Mode the engine will run seemingly normal, but since it is not using the IC circuit to receive the timing signal (it is using the signal internallly generated by the Ignition Module), interrupting the IC circuit in this mode has no effect whatsoever.


The test I gave you does this;

1) holding the shift interrupt switch closed (closes/completes the IC circuit)

2) starting the engine (the ECM will detect normal operation and switch to Run Mode)

3) then letting go of the switch (opening the now in use IC circuit) stalling the engine

Dave
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Old 05-16-2005, 06:31 PM
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Default Re: EFI Gurus wanted

Dave.

What you said makes total scence. I understand the difference between the two switches and will check to make sure I am useing the normaly closed switch and due the test you outlined.

This is what's puzzling me.When I disconnected the wire at the distributor the switch was not hooked up. I had cut the wire before the dist,stipped the ends, touched them together and started and ran the engine. While running I undid the connection and the engine kept running.

I'll let you know how the test work out. Thanks.
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