Where do interupt switch connect

[Technorunner]

Hi. Im doing all the connections for my ECU to my CPI injected 4.3L. vortech converted to mercruiser.
My question is where should i connect the interupt switch? where does it connect on the TBI mercruisers?
I dont know wich one is best to the coil or to the injector. Logical (for me) i should connect it to the injector.
That way i wouldent get any backfire from unburnt fuel the injector squirting in while the coil isent producing any spark. Or is it so short time it dosent get any spark that it wont backfire anyway?

 

[achris]

Re: Where do interupt switch connect

For the MEFI-1 ECU it goes in the white wire that runs between the 4 pin connector on the distributor and J2 on the ECU.
For the MEFI-3 ECU it goes in the white wire on J2 to ground.

You will need to check whether the switch is normally open or normally closed. (MEFI-1 needs NC, MEFI-3 needs NO, I think ).

Regardless, it needs to shut down spark, NEVER fuel....

 

[Technorunner]

Re: Where do interupt switch connect

Thanks !! at least now i know what to "shutdown" Il check it up wich one i need of the to swithes.
is the interupt of fuel to slow for the drive to disengage or is it because of the risk of engine running lean and have detonations??
This is just out of curiosity and NOT "Il try it anyway and see if it work"

 

[achris]

Re: Where do interupt switch connect

Stopping and starting the spark is a lot quicker and more reliable. Back in the day, when the system was thought up, the only fuel system was carburettor and it's not (easily) possible to stop the fuel 'instantly'. I haven't looked into exactly how it's done now, but I know on my MPI it only shuts 3 cylinders off for the shift. It actually makes it harder to disengage, so they came up with 'shift assister', basically a spring loaded plunger that helps pull it out of gear. I dread to think how easy (NOT!) the shift system is going to be to adjust when things start to wear and get a bit of slop in them. The 'shift assister' will be doing it's level best to keep the drive OUT of gear and the slop will ensure that. I pulled it off my previous engine (1994) but the interrupter killed the whole ignition system, so it was just the same as the original 1972 MC-1 drive as far as shift load.

Anyway, good luck with the set up.... You may need to buy a shift assister... Part number -813995A1.

Chris.........

 

[Don S]

Re: Where do interupt switch connect

What ECM are you using? Year? Is the engine an aftermarket marine engine complete? What ignition system are you using?

 

[Technorunner]

Re: Where do interupt switch connect

Il shorten down the story project
I got the boat for almost nothing from a friend with a broken beyond repair 3.0
it was a little bit to weak so i bought my self an CPI vortech 95 astro engine.
now im doing al the wireing for the automotive CPU. The CPU have gotten reprogrammed to go in open loop with no EGR.
all electric components are changed to marine. and of course im building a FWC system to it with a BIG heat exchanger i got hold of from work. It also equipt with a 19" selfadjusting SS prop to compansate the gear ratio. I know some of you will slap your forehead for this kind of project but its fun and will be better gas/milage then a carb and MUCH lesser gas vapors.

 

[Don S]

Re: Where do interupt switch connect

Then wiring colors are meaningless at this point. I have no idea what engine a 95 astro engine had in it.
Marine ECM's are programmed internally for a shift interrupt system. As an example, if you took the ECM off of a TBI engine with a Bravo outdrive, you could not install it on an identical engine with an Alpha outdrive. The ECM's may look identical, but they are not interchangeable.

 

[Technorunner]

Re: Where do interupt switch connect

Its an "Central port injektion" its a half TBI half MPI. I have full control of the ECU pinout and wiring. and the distibutor are almost the same and i checked the schematics and the connector 4 is the same and the coulor white is the same. its Ignition control on ECU pinout.
The interupt switch will be in series in that connection. So it will be normal closed switch i need that will kill the signal and no spark will occur. The only thing i was unsertain of was if i should kill the fuel or spark.
But if you have other thoughts your more then welcome with them. This engine are mated with an alpha one gen1 drive. and are rated for about 215 HP Every thing is almost done. need to install my EM and do the hull thru. Unfortnatly one of them has a casting crack in the Aluminum and i hope to get it replaced from GLM.