Voltage for my pro-tec swap

Jonny Quest wrote: My 1994 was a Throttle-Body Injection and Pro-Tech setup. It came with 3 breakers: 50 amp, 15 amp and 12.5 amp. When I removed all the related TBI and Pro-Tech gear, I could see that I no longer needed the 15 or 12.5 amp breakers. However, I did like the idea of a fuse or fusible link between the "I" terminal on the starter switch /solenoid and my new DUI unit. So, I ran a 12 gauge wire with an in-line ATO 20 amp fuse from the "I" terminal to the DUI. I went with a new "heavy duty" starter switch from NP. At the DUI distributor, I'm getting 11.3 to 11.5 volts. I liked this set-up as I didn't want to use any old Pro-Tech wiring or harness gear. The engine fired right up and hasn't missed a beat in 100 hours since install. JQ

How did you connect the key (engine running) voltage to the "I" terminal?

The "I" terminal is only hot when the key is in the start position. There is only one control line going to the starter relay. When the key is in the start position the "s" terminal is hot and the relay is closed. When the key goes to the run position the "s" terminal is cold and the relay is open. The "I" terminal is used to fire the ignition. After the engine is running the voltage comes from the key to point 41 on the schematic. That's when the dash wiring/ harness connections and their associated IR drops come into play. I think the boats after '92 have improved dash wiring for the ignition circuit so you should be fine. I was just wondering if you still had the original fusible link (assuming you had one) protecting your wiring harness from burning up and your boat catching on fire if there is a short in harness/dash when you turn the key to start. Slight exaggeration but I think that's why it's there but I could be wrong.

There is nothing wrong with JQ's setup especially if there is loss in the old 12.5 breaker it's just slightly different than stock.

JQ,
After thinking about this we are just using different terminology. When I say the terminal is hot I mean that if you remove both wires from it and measure the voltage it will only be there when the relay is closed. I think you are saying there is always voltage there so it is hot. With the key on the voltage is always there but when the engine is running it's coming from one of the wires attached to the terminal not from the terminal itself. If you remove the wire coming from the engine harness your engine will still start but it won't run.

Maybe I don't know the 92+ well enough but that picture doesn't make sense to me. how can the battery and the starter be on the same post?

*and also I edited the thread title. can no longer look at it like that....

Hollywood wrote: Maybe I don't know the 92+ well enough but that picture doesn't make sense to me. how can the battery and the starter be on the same post? *and also I edited the thread title. can no longer look at it like that....

I think they just added an internal relay to the high torque starters. This relay is now just switching the control line and voltage to the "I" terminal rather than the battery voltage. And thanks.

I agree other than according to the schematic on the previous page it looks like PCM used the "I" terminal for the Protec engines. The voltage goes through the fusible link then the 12.5 breaker to the protec connector.   If the key switch has voltage on both the start and run outputs when the key is in the start position that means that the normal ignition voltage is being supplemented by the "I" terminal voltage when the engine is starting. After that the purple wire from the dash/key is the ignition voltage source. Not sure how JQ wired his but I think he has two wires going to his "I" terminal. One to the DUI and the second from the purple ignition wire through the fusible link or without the fusible link directly to the "I" terminal.

TRBenj wrote: Possible, though a little strange that they would have used the I terminal for the protec. I would not use the I terminal as a jumper point for supplying ignition voltage for the DUI. Back feeding voltage into the start relay while running may or may not cause an issue immediately, but it's not appropriate to do so. Hook the 2 wires together and leave the relay out of the equation.

Could you be more specific....which "2 wires"? I am planning on using the wiring method that uses the #26 wire. There is a thread that suggests to cut it from the EMS connector (labeled "P" and 26 on the page 1 schematic) and splice it to one of the wires that formerly went to the trigger connector, A, B, C, or D. Can't remember which. It does not really matter, just need a "red" wire to continue on from the 12.5 amp break to the hot DUI connection.

When you say to "leave the relay out of the equation", is the above method what you suggest?

Looks to me like the ORIGINAL setup in the diagram on page 1 would have the following flowpath when the key is in START. You turn the key and energize the start solenoid, the starter cranks and the "I" terminal gets powered thru the solenoid. From the "I" it goes thru the fusible link to the 12.5 amp breaker thru wire 26 to the ECM (and also the choke)

Now you let the key go to the RUN position, the "I" terminal is no longer powered from the solenoid (since that's how the solenoid is physically constructed) but the power now comes from the keyswitch in RUN thru the 28 wire to the 41 to the 26 wire to the ECM.(and also the ckoke).

Kind of an odd use of the "I" terminal but it works and seems like you get the highest voltage to the ECM when starting (basically a shorter flowpath without going up to the dash during the START phase. (Big contacts in the solenoid straight to the "I" terminal).

There are at least a few points you can hook in for DUI power from the looks of it.

By the way I can barely spel ElekTrickal but this makes sense to me.

I think Desertskier has already pretty much said this.

Guys,

My system is wired EXACTLY as shown in the starter / solenoid switch diagram I recently posted. The "I" terminal has nominal 12V when ignition switch is in either run or start position. Turn key on...power to DUI. Turn key to start...300 ponies roar to life. Turn key off...engine shuts off.

It appears that there are several possible wiring options to solve the "how to wire DUI" question. My comment is that the method I used works well and was very simple. I have NO ProTech parts left on my rig.

JQ

4 people that I know of (including myself) have done this swap since I created the write up a little over a year ago. Each one worked perfectly fine. I'm confused as to why this is such an issue on this install?

I say install it per the write up and if you have any issues afterwards, let us know what they are and we can hopefully get you up and running.

malcolm2 wrote: BTW my "I" term is hot on key position 1 (on) and 2, so Rob's suggestion would work on my old relay. Not sure about the new relay, have not done the final measurements with the new starter. Once I get that, you can say, "5 people that you know of".

Sorry, but this is driving me nuts. The "I" terminal is absolutely not hot when the key is in the run position. Yes, you measure 12V when you put your meter on it but the voltage is not coming from the relay terminal. It's coming from the wire that is attached to the terminal. Disconnect the wire then turn the key to run and you will read 0V on the terminal. I will stake my electrical engineering degree and 34 years of experience on this.

KENO wrote: This is for Jonny I'm sure your way works and is pretty straightforward using the "I" terminal, but you seem to think that the "I" terminal is powered internally from the solenoid when the key is in RUN. The solenoid isn't built that way.(you need to do a little solenoid research) In START the "I" is powered internally, in RUN in this application, it's getting power from an external source as previously posted by Desertskier and me. In many applications (non Pro Tec) the "I" terminal has NO POWER in RUN as stated by TRbeng and isn't even used unless you're bypassing a ballast resistor on startup in some applications. Lots of solenoids out there with no "I" terminal at all on the solenoid. I'd say your info is sketchy and incomplete making it hard to follow what you're saying unlike the JPASS writeup. I also agree your method is simple and works good, just explain it better..

KENO:

I'll be the first to admit that I'm not an electrician (but I do play a rocket scientist on TV). As such, I did some initial fact-finding on starter switches / solenoids by raising this question to a couple of local master mechanics. One guy in particular started turning wrenches back in the '70s. Both guys I spoke with told me that certain starter switches / solenoids have the "I" terminal that can be used for this specific purpose.

I did not do any write-up on my specific procedure, as JPASS did such a good job on his Pro-Tech swap-out. I didn't feel I could really add anything substantial to his work. That said, I did do things just a little different than JPASS, but our methods were very similar in principle and theory. There are several ways to accomplish the same goal. If folks are comfortable with re-wiring the PCM/Pro-Tech wire harness, then that is a solution that has produced good results. I'm simply stating that I went with a slightly different approach that has also yielded good results.

I simply did not want any Pro-Tech gear left on my engine. Same with the old TBI gear. I pulled everything off. (The only exception is that I left the oil pressure and water temperature switches in place). This methodology caused me to go in a slightly different direction when it came to wiring the DUI. I just ran the tach out to the gray wire on the wiring harness. Then I ran the 12V feed to the DUI from the "I" terminal. I did install a 20 amp fuse in-line for protection. That's it -- 2 wires.

I'm not advocating that anybody follow my procedure as this is for informational purposes only.

JQ

Jeeez....tough crowd.

Hollywood: I am all about learning and gathering knowledge. Please help me understand how these solenoids work, then. Is there a better way? If so, then I'm all over it. With no Pro-Tech wiring or parts, how would you recommend providing 12V power to the dizzy? What advantage would I gain over how I have it wired now? Is the way I have the system wired prone to failure? Will the solenoid fail due to the current wiring? Will the DUI unit fail due to the current wiring?

Not defending myself here...just trying to understand advantages / disadvantages to changing from a system that is working fine.

JQ

desertskier wrote: Sorry, but this is driving me nuts. The "I" terminal is absolutely not hot when the key is in the run position. Yes, you measure 12V when you put your meter on it but the voltage is not coming from the relay terminal. It's coming from the wire that is attached to the terminal. Disconnect the wire then turn the key to run and you will read 0V on the terminal. I will stake my electrical engineering degree and 34 years of experience on this.

So the "I" term has wire #26 on it and goes to the 12.5amp breaker where it meets up with the wire coming from (or going to) the ALT... goes thru the breaker and to what used to be the "P" of the ESM connector (now the hot to the D.U.I.)

Where is the 12v coming from to get to wire 26 connected to "I", at key position 1? The ALT is not turning since I am just turning the key and the motor is not running. And more importantly, were will the 12v come from to get to my D.U.I. if it is not coming from "I" term when the key is at 1?

I can follow directions and JUST DO IT, but I am curious as to why or how it works. I am a lowly Industrial Engineer and had to remove my "occupation" on my profile, cause some folks say stuff like "what kind of engineer are you", when you are curious or ask what they think is a stupid question..... so be gentle.

Apparently PCM does not understand the inner workings of the starter relay as their wiring diagram has the "I" terminal providing power to the electric choke and to the Pro-Tech control module. Am I missing something?