HAILERS

Actually it's a voltgage switch that incorporates a relay in it. I bought it from JAYCAR. It comes with four pages of instructions in plain language. It requires some soldering of the parts to the board.

A jpg that is attached with this post shows a simple schematic of the wires to the switch. You use the output of the water thermo sensor (green wire with white stripe) as an input to determine when the switch will complete the circuit to pin 3B to the ECU.

Over 120 degrees temp and the circuit should be open to 3B so the car will start with higher temperatures. Any temp under that, and the circuit will close and make it a normal factory circuit for 3B, so the car will start easily when the temps are cooler.

I labled the Relay on the board. The relays output/input is on those screws showen above it where I show the Black/Blue wire.

Bottom line: If I made it, ANYBODY can make it. Fact.

https://www.rx7club.com/forum/showth...203post6003203


I got the idea from this site: http://autospeed.drive.com.au/cms/A_2476/article.html

AsianFlip06

hmmm u talking bout this plug connector? I was lookin at my ECU one day and saw this red looking chip spliced on the black/blue wire.... Here is a pic uploaded

HAILERS

Well it looks like it goes to 3B (bottom row, far right on the plug), but what you call a chip looks more like a home made splice with some red celophane tape around it to protect it.

Do you know or have you followed to see where that piece of speaker wire is going to????? The one that comes off the red outfit?

At least one of the two looks like spreaker wire at the end opposite the black wire. Have you followed either of those two wires to see where they lead to????

IF that is red cellophane tape, maybe you could peel it back and take a picture of what is underneath.

Fitness Stain

will any switch work, or does it have to be rated for a specific amperage/voltage/whatever

im going to do this tomorrow i think, and im going to buy a simple rocker switch like the one that landers used in his fuel cut off switch writeup ... will that one do? i just have to extend the wires and hook each wire to the switch right?

HAILERS

No. That circuit carries little current. It's 12vdc ONLY when the key is HELD to start and no voltage at any other time.

Like I said, it carries zip in the way of current. It's just a signal to the ECU that we are now in the start position.

Even a 5amp or less switch will do. Heck, even a one amp switch would do the job.

boost_its_what_for_dinner

okay this hot start problem is one i know all to well. but riddle me this mine will start when hot but only if i hold the gas to the floor and crank for a few seconds, so i thought maybe my afm was bad since the air flow meter controls the fuel pump kicking on and off so you know if you roll your car it doesnt flood the place with gas but i need to have some one else try this way of starting so i can make sure that mine is not different than other hot start problems plz let me know soon oh samll side my car also cuts out in boost at the slightest boost load cuts out but the turbo stills spools in the process but motor doesnt make power its like a fuel cut but dont know why im running factory boost and i have a aftermarket gauge

Fitness Stain

awesome. thanks for the info!

boost_its_what_for_dinner

okay this hot start problem is one i know all to well. but riddle me this mine will start when hot but only if i hold the gas to the floor and crank for a few seconds, so i thought maybe my afm was bad since the air flow meter controls the fuel pump kicking on and off so you know if you roll your car it doesnt flood the place with gas but i need to have some one else try this way of starting so i can make sure that mine is not different than other hot start problems plz let me know soon oh samll side my car also cuts out in boost at the slightest boost load cuts out but the turbo stills spools in the process but motor doesnt make power its like a fuel cut but dont know why im running factory boost and i have a aftermarket gauge

AUGieDogie

iTrader: (4)

Holy ****!!!!! I had that exact setup installed in my 87 T2. It worked for years but doesn't now. I could never find any info on it, and the shop that put it in for me closed down.

AUGieDogie

iTrader: (4)

OK I've calmed down now. Just never seen or heard ANYTHING on this little device.

I had it installed in about'98 and it work for about 4 years just fine. I have no idea what it is or how it was made. A local import shop installed it. 2 of the wires where spliced directly inline with the starter wire (3b) and the other wire goes to ground. After I had problems with hot starts agian, I discoverd that if I switched the wire to ground it would work start normal when cold and start normal when hot IF the ground wire was switched off. Since then I have discoverd that It works just as well with the whold assembly removed and just a switch on 3b.

I'm going to try and find the circut/device/thingy.

AUGieDogie

iTrader: (4)

Bingo!! got it in my hot little hand.

What do you wanna know?

HAILERS

It'd be interesting to see a jpg of it off a scanner or camera with the thing exposed and not covered up with tape etc.

BinaryRotary

You mean theres cars without a hot start problem?

AUGieDogie

iTrader: (4)

I Uncoverd it last night. It looks like the reason it stopped working was that a capacitor became dislodged. I'll try and post an image of it, if i can figure out how.

AUGieDogie

iTrader: (4)

Here we go

88RX7T2

iTrader: (1)

Has anybody find out how this device works, Can we get some schematic made so we can duplicate it.

AUGieDogie

iTrader: (4)

I havnt' a clue how it works. I've been too busy with my vert projects to fix the capacitor, and re install it. I was kinda hoping it would be useful to some one.

jayroc

I have a hot start problem too, but it's not so bad I need to wait a few minutes to start again. It starts the second time usually. You can smell lots of fuel at that time, though.
I'm thinking it is BAC related, or my FPR is being overwhelmed, but after reading this thread, I'm not so sure. The previous owner installed a walbro and my car is a s4 NA. He also installed a starter button, but I reverted to stock. As I remember, it had the same hot start issue with the button which is in effect, removing the 3b wire from the ECU.

Basically, as I understand the problem, the cranking pulsewidths need to be leaner on hot starts? 17ms seems like a lot of fuel to me for 190 degrees. Last year I did a lot of tinkering on my 12a with starting pulsewidths and megasquirt. IIRC anything above 16ms would flood the engine or foul the plugs on hot starts.
I have a megasquirt stand alone setup that I'll be installing soon (into my FC) and am very curious about the stock cranking pulsewidth table. Muythai has already gotten a tuned cranking pulsewidth table for the MS people, and I'll be using it, but I'd like to see some stock numbers too. Does anyone happen to know if there is a stock priming pulse, btw?
I think in the FSM it says something like "...it uses a predetermined amount of fuel during cranking" based off the start condition and water thermo temp...
Anyways, going back a couple pages I think Hailers measured something like:
189.5 degrees 5.96ms pulsewidth (not using the stock table, ie. 3b disconnected)
209 degrees 17.62ms pulsewidth ('predetermined' stock ECU setting)
I'm not sure what the megasquirt table numbers are at the moment...

HAILERS

That's about the gist of it. About 5.96 with the 3B disconnected and about 17 with 3B connected. Absoulutly no problems on a hot (actually pretty normal temps) with the pw at 5.96 but problems if the pw is 17.

That part about him having a button to start the engine is a little vague to me. I'd take some convincing to me that the start signal wasn't going to 3B when he pushed that button.

Anyway, you do understand that when the engine is cool and 3B is disconnected, then the start pw at 5.96 is a bit too lean and makes for a difficult cold start. That's why introduced a switching device operating off the water thermo sensor to allow during cold starts for 3B to be in the circuit when the water temps are below something like 120 degrees (Actually I've forgotten the exact figure I set the switch at).

jayroc

I was thinking the 'start signal' came from the column ignition switch, but I haven't looked at the wiring diagram so correct me if I'm wrong... The reason I say that it wasn't getting the 3b start signal is because the way the guy had it wired. He used the stock wire to send the start signal to the starter, but cut the wire from the column. So if the ECU expected the key to go to the start position and never did, it wouldn't know it was in a start condition. A starter button in parallel with the stock would work to provide the signal, but it depends on where you cut the wire..
If it took the signal from the starter (which I think the 'sub-zero motor' does?) then it would know, but I don't think that's the case. (or maybe starter relay?) The other reason I think it wasn't getting the 'start signal' with the button is because I could turn the key to start and the accessories would turn off,(idiot lights, radio, etc) but not if I used the button. I assumed it was part of the same circuit to send the start signal to the ECU..
I bought the car in february or march this year and converted back to stock ignition in april, so I can't remember now if the cold starts were difficult or not.

HAILERS

Yeah. It all depends on just how he wired the start button.

NZ_87_TURBO

Sorry to drag this thread up again.
Ive just reread through the whole thing and have a couple of questions regaring my own hot start issue.
If i turn my car on from cold then turn if off again after 5 seconds(could be any mount of time ) then it will flood. I havnt installed a fuel cut switch yet so have been diconnecting the fuel pump to start again.
judging by what you have said then this solution wont fix my problem due to no change in temp coming from the water thermo sensor anyway.
I can test this by a) unpluging the sensor and it will defaut to a hot temp
b) removing pin 3B from the ecu
both of these are checking the same thing right?
my injectors have been cleaned and tested for leaks but you never know they may have done a **** job and there fuct.
any ideas

HAILERS

I think you read me 180 out.

If 3B is disconnected and the engine is cold and the weather is cool to cold, then that would result in a lean fuel mixute during start because the ECU would be injecting fuel using the AFM signal instead of the *Start Fuel Map* in the ECU.

3B would make for a more difficult start than normal when the engine is cool/cold because the fuel mixture would be leaner than what is usually required with a cold engine.

I made the Simple Voltage Switch so I would never have to use a fuel cut switch anymore, and I have not since I made and installed it.

You've confused me a little by first talking about Hot starts then describing a cold start problem.

If I were you I'd just make the fuel cut switch and mount the switch on the plastic surround on the steeing column and see how that works out for you.

EDIT: About the cold start problem. I'd guess that if you had a switch to interrupt the signal to 3B, that would lean out the mixture when you go to start, so that might very well aid a cold start flooding issues like you describe. But it that is the case, I'd do the fuel cut switch because it's easier, what with being closer to the igniton key and all.

NZ_87_TURBO

haha, cheers mate. will do.
Basically what im trying to say was= my car floods even when its not "hot" but not from the first start ( in a few hours/cold )
the water thermo sensor should not be sending any different signal to when it first started. I did find tho that if i turned the car off when reving to 3 grand it would start again. is this indicating leaky injectors?

HAILERS

I'm not big on leaking injectors causing problems. Personal predjudice I suppose.

The early series four are known for a QUIRK on starting. It goes something like this: Go out to the car and move it from the driveway to the front of the house and shut it off. Come back later, say fifteen minutes or longer even, and go to start the car. Won't start. Flooded. Blame MAZDA. It's their fault. Bad design.

I don't think the later RX have this QUIRK. But it's a known quirk. I'll try to find a post/thread that describes it better. That said, I've a 86 n/a, 87 turboII and only experienced this quirk a few times. Maybe three/four.

Try this link, It mentions the three grand like you did: http://www.rx7.com/techarticles_floodprev.html