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Old 07-24-2006, 01:47 PM   #1
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http://www.msefi.com/forums/viewtopic.php?t=20871

So, does a miata FP relay have continuous 12V on the coil side?

If so, will this be sufficient to keep this from happening again?
Quote:
Originally Posted by kingofl337
1.6L Fuel Pump Relay
I also had to add a relay to switch the relay for the fuel pump. The megasquirt fires the fuel pump by shorting pin 37 to ground. But, Mazda uses 12v to switch the relay for the fuel pump on the 1.6L. So I spliced into the MAF cable there is one plain black wire in the harness. This is the wire that needs 12v to switch the OEM relay on the 1.6L.
I used an automotive relay to convert the megasquirt fuel pump output to 12v.
Pin 87 was the black - fuel pump relay wire that needs 12v.
Pin 30 and 86 need to be connected to +12v
Pin 85 was connected to PIN37 on the megasquirt.
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Old 07-24-2006, 06:15 PM   #2
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Quote:
Originally Posted by Al Hounos
http://www.msefi.com/forums/viewtopic.php?t=20871

So, does a miata FP relay have continuous 12V on the coil side?

If so, will this be sufficient to keep this from happening again?
No, it does not. The circuit opening relay provides power to the FP when the light green wire is grounded. The 12v into the COR is provided from the main relay, which is obviosly switched. Why add the complexity of an extra relay when you can let the OE equipment do the work?

Do it the easy way. Remove the kickpanel under the steering column and find the circuit opening relay. It has 5 wires coming out of it; blue/black, white/red, violet, black, and light green. Connect MS pin 37 to the light green wire and you're done. This is the same wire as the lt green wire at the MAF and diagnostic port, check for continuity if you're unsure.

The above is based on the 1990 wiring diagrams, since you don't have your year listed.

Last edited by mschlang; 07-24-2006 at 06:32 PM.
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Old 07-24-2006, 07:48 PM   #3
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It's a 1992. I was under the impression that the stock ECU supplied 12v to the FP, therefore, a ground will not work as a trigger, that's why the relay. In the same post that I quoted, he describes exactly what you do, but only for 1.8 miatas.

https://www.miataturbo.net/forums/showthread.php?t=2217
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Old 07-24-2006, 08:43 PM   #4
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Quote:
Originally Posted by Al Hounos
It's a 1992. I was under the impression that the stock ECU supplied 12v to the FP, therefore, a ground will not work as a trigger, that's why the relay.
I don't believe so. Check out

http://www.madracki.com/miata/images/wiring/92diag.pdf

specifically C4 and A22. When the COR is grounded by light green, wht/red is connected to blu/red, giving the FP 12v. At A22, you can see that the FP has 2 wires, blu/red and black.

Check out C7. Here you can see that the AFM turns on the FP by grounding light green to ground. Same thing as a paperclip in the diagnostic port.

Quote:
Originally Posted by Al Hounos
In the same post that I quoted, he describes exactly what you do, but only for 1.8 miatas.

https://www.miataturbo.net/forums/showthread.php?t=2217
Well, us 1.6 guys don't have it quite as easy. He is talking about connecting pin 37 to the light green at the stock ecu. No AFM means no FP switch (C7), so the ecu does the grounding. To do the same thing on a 1.6, you have to find the COR, and that dang light green wire, under the steering column.


Wiring diagrams are you friend
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Old 07-25-2006, 02:17 AM   #5
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Al your best bet is to wire the megasquirt directly to the ECU test connector to jumper the fuel pump on. You should wire it directly to the megasquirt. The 90-93 doesn't use the ECU to run the fuel pump. The 90-93 ECU does not operate the fuel pump the AFM does.
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Old 07-25-2006, 12:47 PM   #6
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I am glad I waited to hook this up. I was reading the same thread that Al was about the 1.6 FP. When it said find the black wire in the MAF harness and connect it to 12V, I tried that and tripped the breaker. So I temporarily connected the light green wire to ground so that it runs when my key is on. I don't mind wiring a relay, but I just haven't had time. I hadn't made the connection yet that MS pin 37 sends out a ground to fire the pump. That's good news, I will wire that up tonight!

BTW, what does COR stand for?
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Old 07-25-2006, 12:54 PM   #7
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Ok, but would that prevent the problem that I had? The fuel pressure would still be plenty high enough to flood the engine, even without the fuel pump running. I still don't understand why the injectors stayed open, whether it was injector drivers failing or something else.
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Old 07-25-2006, 04:12 PM   #8
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Quote:
Originally Posted by Fulltilt
I am glad I waited to hook this up. I was reading the same thread that Al was about the 1.6 FP. When it said find the black wire in the MAF harness and connect it to 12V, I tried that and tripped the breaker. So I temporarily connected the light green wire to ground so that it runs when my key is on. I don't mind wiring a relay, but I just haven't had time. I hadn't made the connection yet that MS pin 37 sends out a ground to fire the pump. That's good news, I will wire that up tonight!

BTW, what does COR stand for?
COR = circuit opening relay

The black wire at the airflow meter is a ground. The problem with leaving the jumper in at the diagnostic connector is that in case of an accident, the FP will continue to run as long as the key is on. Hopefully nothing's burning
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Old 07-25-2006, 07:20 PM   #9
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updated my thread. confusing.
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Old 07-26-2006, 12:04 PM   #10
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So, Al are you running?
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Old 07-26-2006, 12:42 PM   #11
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Yes, but I really don't want that to happen again. Not only would it strand me, it fouled all my plugs and I'm sure it isn't good for the engine. Needless to say I won't be leaving the key in the on position while it isn't running, but I'd like to have a better solution if possible.
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Old 07-28-2006, 06:11 AM   #12
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Once you hook the megasquirt to the fuel pump it will turn off after 2 seconds of the motor not running.
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Old 07-28-2006, 09:12 AM   #13
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But I agree that fuel pumps are not the problem. The injector should never come open without a signal. The residual pressure in the rail will allow a lot of fuel into the cylinder.
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Old 07-28-2006, 04:01 PM   #14
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Yes exactly, and it appears my msefi thread has died before a solution has been found, something you'd better get used to.
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Old 07-28-2006, 08:23 PM   #15
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Just got back from another boostin drive. Since it seems it is not the cause of the problem, I will most likely leave the paperclip setup in place. I like it because it makes a nice immobilizer.
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Old 07-29-2006, 03:46 AM   #16
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Hi Al, thanks for reminding me (on miata.net) about this forum. Ive spent a few hours lurking to try to get what I can out of it b4 I start posting noob questions. I would have PM'd you, but it wont let me until I get to 10 posts. I also would like to know if you would be alright with talking to me on the phone sometime for a bit to clear stuff a bit since there is soooo much reading to digest and frustratingly little information.

For those who dont know of me, I am working on squirting a 90' 1.6. I am rebuilding the engine right now and I have a BEGi 1.6 turbo kit equivalant to FM1. I'm really excited to get working on this, but its a bit overwhelming.

Anyway, Ill be hanging around here quite a bit for the next couple months or more
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Old 07-29-2006, 02:33 PM   #17
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I really don't know all that much, but you can learn from what I learned the hard way. Just search for threads I've posted in this forum. the two big things that really held me up should be solved for you. they were the spark side of the resistor confusion, and the low impedance injector interference. You should be able to get your MS running in half the time I did.
have you found the instructions on diyautotune?
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Old 07-31-2006, 11:17 AM   #18
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My fuel pump runs from MS now. Strange though, when it's cold, the FP runs constantly when the key is on and the engine is not, but when it is warmed up and I turn the key on, it runs for two seconds then turns off like it should. Don't know what that is about, but it's better than key on FP on 100% of the time. Anyone else experience this?
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Old 07-31-2006, 08:18 PM   #19
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I have found the diyautotune instructions, picked away at parts of the megamanual, and read lots and lots of threads. I am getting a better understanding of things the more i read. I just figure it takes some time. Thanks for the help so far
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Old 08-01-2006, 09:03 PM   #20
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Quote:
Originally Posted by Fulltilt
My fuel pump runs from MS now. Strange though, when it's cold, the FP runs constantly when the key is on and the engine is not, but when it is warmed up and I turn the key on, it runs for two seconds then turns off like it should. Don't know what that is about, but it's better than key on FP on 100% of the time. Anyone else experience this?

Did you clean the bottom of your board? The MS should turn you fuel pump on
for 2 seconds and then shut off all the time.
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