SKDZ-EZ V6 ADub

[Mr-Paulio]

And she's back on all fours,

mounts painted and installed. Everything else ticked off the list. Just need to work on that pesky fuel pump wiring this weekend. Hoping to make the next run, all legit!

[Mr-Paulio]

Jim might be able to help on this one as he knows megasquirt ECUs better than me.

All you need is for the ECU to supply a signal to the fuel pump relay so it only runs when the engine is running. The ECU should have a system to allow this.

So you need to wire up a relay that has fused power to the pump from the battery or another high power constant power source and then the switched part of the relay to the ECU.

Based on the mega squirt ECU DB37 connector you should have pin 37 (Purple?) connected to the relay solenoid, pin 85 and pin 28 (Red?) 12V+ from the ECU to pin 86 on the relay. Then connect fused 12V+ from the battery to pin 87 of the relay and the +ve connection of the fuel pump to pin 30 of the relay. Then the -ve pin of the fuel pump earthed to the car body.

https://www.diyautotune.com/support/tech/other/grounds/

http://www.aaroncake.net/rx-7/megasquirt/WireInside.asp

Well I have hit a wall again... HELP!
From what you guys have said, and my own research, pin 37 is the one to run the fuel pump from the ECU. I tested this, and all the other pins. But none of them have voltage when the engine runs and then drops voltage when its only ACC (After the 3 sec prime, time) To be honest the wiring is a mess inside the plug! I broke a wire testing as its so shit, and I would rather not mess with it anymore. Very dodge wiring job with this ECU!

So back to my plan A??
I ideally need to find a new supply for the relay that only has voltage when the engine is cranking/running? If that exists? I cant think of anything??

My next option I guess would be to find a vacuum switch that is normally open. Fit this in the relay trigger wire and therefore the fuel pump will not run until their is vacuum. And hopefully the engine cranking creates enough vacuum to close this switch and run the pump. (I haven't found a switch yet, open to ideas)
I know often this is done with an oil pressure switch. But this will be a lot harder on my car as I would have to make an additional oil line with a tee in it to be able to fit the switch in. As I currently do not have one, and the gauge is using the only existing location. And the vacuum hose for the ECU passes right beside the fuel pump relay.
Thoughts? Help??
Thanks in advance as always guys!

[GDII]

Can you access the ECU software and check that pin 37 is active. You can go into the ECU and cut signal to injectors or coils if you want, at least I know on some you can. Maybe it's turned of and who ever did the tune wasn't worried about it because the car worked and the pump ran because it used another system.

[Mr-Paulio]

Can you access the ECU software and check that pin 37 is active. You can go into the ECU and cut signal to injectors or coils if you want, at least I know on some you can. Maybe it's turned of and who ever did the tune wasn't worried about it because the car worked and the pump ran because it used another system.

I have no idea how to do this! Haha.
But yeah, it is probably worth looking into, if outputs can be turned off. And I have left the wire from 37 connected in case.
Ideally I just want to get it to pass the cert for now anyway. If there is an easier, faster way? Was hoping to have it resolved this weekend. As it's the last task on my list!

[GDII]

Jim should be able to help you through it, I have no experience with the MS software but can do research to find out.

I tried downloading it but my mac won't let it install....

This image is the best I can find right now. Not sure how you would access this menu though.

[JasonFriday13]

From what you guys have said, and my own research, pin 37 is the one to run the fuel pump from the ECU. I tested this, and all the other pins. But none of them have voltage when the engine runs and then drops voltage when its only ACC (After the 3 sec prime, time) To be honest the wiring is a mess inside the plug! I broke a wire testing as its so shit, and I would rather not mess with it anymore. Very dodge wiring job with this ECU!

Sounds about right. The outputs on the ecu aren't actually outputs, all they do is ground the wire that's connected to it using a transistor (an electronic version of an on/off switch).

So the fuel control chain should look like this (one wire): Battery positive -> EFI fuse -> EFI relay contacts -> Fuel pump relay coil -> ECU fuel pump out (pin 37).
And the fuel power chain should look similar to this (one wire): Battery positive -> Fuel pump fuse -> Fuel pump relay contacts -> Fuel pump -> Ground.

On most MR2's, the positive side power is the same up to the fuel pump relay, which is called the 'circuit opening relay' or COR for short.

[edit] If you have a separate fuel pump fuse and relay, you can run the control wire from the same fuse as the fuel pump.

Something similar to this (yellow wire is positive, white is the control wire to the ecu, the unused terminal on the relay goes to the fuel pump):

[Mr-Paulio]

Sounds about right. The outputs on the ecu aren't actually outputs, all they do is ground the wire that's connected to it using a transistor (an electronic version of an on/off switch).

So the fuel control chain should look like this (one wire): Battery positive -> EFI fuse -> EFI relay contacts -> Fuel pump relay coil -> ECU fuel pump out (pin 37).
And the fuel power chain should look similar to this (one wire): Battery positive -> Fuel pump fuse -> Fuel pump relay contacts -> Fuel pump -> Ground.

On most MR2's, the positive side power is the same up to the fuel pump relay, which is called the 'circuit opening relay' or COR for short.

[edit] If you have a separate fuel pump fuse and relay, you can run the control wire from the same fuse as the fuel pump.

Something similar to this (yellow wire is positive, white is the control wire to the ecu, the unused terminal on the relay goes to the fuel

You know I was just wondering this last night. If the ECU switches grounds. Awesome!!
So in theory all I have to do is put pin37 wire on the ground side of the relay coil. Previously I had a ground on one side and pin 37 on the other, (ground both sides) durrr!!
Thanks Jason! Will try this out today

[GDII]

When actual practical experience is better than theory!

[Mr-Paulio]

Okay, so that worked mint! Thank you guys! Once again... Love you all!
One point I'll add though. The idea of running the relay 12v off the battery with the fuel pump feed doesn't work. (At least they way mine is set up)
My 12v to 5he relay coil was already wired like this. With pin 37 used as a ground on the relay it primed, stopped and started again when the engine cranked.
BUT,
when I switched the ignition off the fuel pump ran again. (Less than ideal!) Obviously pin 37 drops back to ground with the ignition off. Easily solved though. I just rewired 12v to the relay coil from an acc wire. Now working mint!
Time to get that cert now!!

[GDII]

That's excellent!

Yeah the fuel pump relay needs a switched power source that is controlled by the key rather than going straight to the battery.
If you have it setup like the MS wiring diagram then you are all good. Sounds like this is what you have now anyway.

[JasonFriday13]

BUT, when I switched the ignition off the fuel pump ran again. (Less than ideal!) Obviously pin 37 drops back to ground with the ignition off. Easily solved though. I just rewired 12v to the relay coil from an acc wire. Now working mint!

The 12V wire for the relay coil should really come off the main EFI relay, because the fuel pump should only run when the key is in the ON position. The majority of cars are wired this way. My car actually has two relays, I've used the stock wiring but instead of a fuel pump it's connected to the coil of another relay, which switches the fuel pump straight from the battery.

[Mr-Paulio]

No car updates.
She's just sitting there patiently wait for a cert.....

Meanwhile....
I made some workshop wall art!!

[Mr-Paulio]

Yay!!!
See ya all at the next club run Auckland folks

[GDII]

That's great news. Glad you got all the little bits sorted and the fuel system working safely.

[Mr-Paulio]

That's great news. Glad you got all the little bits sorted and the fuel system working safely.

I thought that would be the hardest part. Turned out to be easy! Thanks to you guys