Help with Braineack built MS3 - fuel pump circuit
 

I'm working on a MSM with no fuel pump. I've tested the FP relay, and it's functional with continuity to the ECU plug. When grounded there, the relay is working and the fuel pump is turning on.

Continuity is also good on the MS harness from the ECU plug through the DB37 plug.

What should I be looking for on the MS3 board itself? I've also tested that pin and it is not grounding when tested in test mode. It appears to go to D4? Does this fry like the older MS1/2s? Is there a fuse that needs to be removed? Sorry for lack of knowledge on this project, no documentation was given to me after the owner gave up trying to get it running.

who's MS is this?

I ask about who's unit it is, because if it was built for a regular NB2 and not MSM specifically, then the FP won't run (along with other things). But it sounds like it's getting 12v...

Can you confirm what pin the purple fuel pump relay wire is populated on the ECU connector? First thing "mechanical" I'd want to double check. It should be at 2M between 12v and Injector C.

Craig J., GTred on the forum. I don't know if he bought it new from you though.

no, he didn't from someone else here in the FS section IIRC.

Ok, do you have any documentation for it, or have any idea which one this is?

I THINK it was this one: Redirecting

I remember GTred asking me for info getting setup a while back, but havent heard from him in months.


harness should be built to this:

https://lh3.googleusercontent.com/Lz...=w1445-h578-no

by any chance did you check the priming pulse settings? i had no fuel pump issue found out my ms2+ reverted some of its settings to all 0's

He tested it with test mode. So that wouldn't be the problem. I may end up taking it apart to test some of the components.

Yeah I appreciate the willingness the lend a hand Aidan. Once the circuit was tested all the way to the DB37 cable, it's outside of my knowledge base. Test mode did indeed provide neither fuel pump operation and/or continuity to ground.

I'd say just send the unit back to me and I'll figure it out and get it back, but I leave for a two-week vacation on the 21st--unsure if we can make that happen in time.

Confirm I didn't put the fuel pump output wire on the wrong ecu connector pin, then we can open the case and see if maybe there's something obvious on the circuit itself, like bridge leads on the Q2 and Q24, or D4 backwards, or R16/R40 missing, or something.


There's a very subtle difference between how a normal 01-05 gets power and how an MSM does as well, so we should also confirm this unit/harness was built for an MSM.

In the meantime if you really just wanted to get it up and running, you can still jump f/p in the diagnostics box.

Fuel pump is wired to pin 37 of the lower (main board) connector. It's the single track on the top right of the pins shown on the bottom of the board below. It then jumps over the track directly to the left, and it's other pin is right below where it says "IAC2A". That pin has continuity to the black (ground) wire in the same DB37 cable.

https://www.miataturbo.net/attachmen...ine=1463150423

And the top of the board for reference:

https://www.miataturbo.net/attachmen...ine=1463150423

I know that injF (G?) is on at -100 coolant temp, I think that's the "subtle difference" you're referring to.

omg.

I put the large resistor on R39, not R40.

The fatty right above r40, is that r39? Fuel pump related? Just move it?

Yes. R40 is needed for the fuel pump. R39 is usually not populated. Just move it to r40

correct. the big fat 1ohm resistor needs to move from R39 to R40.

R39 is the unused idle mainboard controller circuit.

without R40 connecting to ground, the transistors on the fuel pump circuit have nothing to send to the relay. :(


feel free to:
:slap:

For reference here is the fuel pump circuit.

https://www.miataturbo.net/attachmen...ine=1463243704

Without r40 the entire circuit is useless.

That's easy enough, thanks!

It sounds like you have already got this figured out, but here is a link to the classified ad that I purchased this thru: https://www.miataturbo.net/miata-par...s3x-msm-85646/

Thank you all for the assistance.

Anybody have the msm specific ait resistances?

here

Thanks, kinda saved my ass. Those settings were -7 with a 24900 bias resistor, and 70 with a 249000 bias resistor. Worked well enough to get through the dyno tuning, but it wasn't reading correct. Anyone know the correct bias resistance?

For the MSM:
https://www.miataturbo.net/attachmen...ine=1463658293


everything else seem to be okay for you guys?

Yes, resistor swap fixed the fuel pump, car dynoed at 247. Much more and he needs injectors/rods.

Alternator sucked, running 11.2-12.7volts the whole time. He said he had some issue with the ecu regulation, on the old ecu, is the MS setup to regulate one? That or he needs a 94-97.

it should be.

double check the voltage at the injectors actually matches what the MS is suggesting. The Alternator settings are on the first tab, and it should be pretty solid at around 14.5v. Those settings are from DIY and are pretty spot on for all other NB installs.

Need help with a fuel pump issue on my MS3X. This is for a 99 using the MSPNP-pro base map.

I'm not able to turn the fuel pump on. Everything else works. When I jump the FP pin on the diagnostics port to force to pump to run and start the car it works just fine. As soon as i disconnect that jumper the FP dies and the car will slowly start to run lean and finally stall when it looses enough pressure.

When I use test mode to trigger the fuel pump I can not hear it running.

I've set it up on the bench in test mode and am reading 0.6V with the output set to off, 4.6V with is set to on, 1.7V when pulsed at 25% DC. So it seems to be functioning. I'm not sure why it's only 4.6 V. Battery in is at 12.4V. The 5V on the proto is 5.08V.

I've attached a picture of the circuit and all diodes look to be the right way. All diodes look to be in the right orientation.

When I swap it back to the stock ECU it primes and starts right away without needing the jumper. I'm stumped

https://cimg8.ibsrv.net/gimg/www.mia...5c352e21ce.jpg

It's not providing power to the fuel pump, it's giving the fuel pump relay ground. So you'd wanna check for continuity to ground when switching the fuel pump on/off. But if it has 4.7 volts that's not a good start.

that makes more sense. Well no continuity to ground when I toggle on or off the test mode FP output. Any ideas? It looks like the FP I/O is not user selectable to switch it to a different output.

what output do you have the FP on? The MSPNP-PRO map isnt going to match inputs and outputs exactly...

It's maped to the fuel pump pin. the drop down option to re map the output is greyed out and looks like it can not be changed. When I'm in test mode and toggle the fuel pump pin it see a voltage change on the multimeter so the I/O seems to be working from the CPU. I'm guessing I toasted some component when I had my harness miswired earlier.

current plan is to order the components of that circuit and build it on the proto area and bypass the original circuit.

well it's completely possible you installed the wrong transistor on Q4

yup, anything is possible with my noobness on this project.

would it be possible to use i different I/O pin for the fuel pump. It looks like it can not be remaped in the fuel pump setting page. But in the programmable on/off setup one of the inputs is fp_duty. So if I set the fuel pump to open loop pwm then setup a programmable output to trigger on when fp_duty > 0 and wire that to the fuel pump harness pin would that work?

Is there a suitable output on the MSX card to control the FP relay without extra circuitry?

Why are you using PWM. Do you have a solid state relay?

No, the default FP circuitry is not working. I probably shorted something and damaged a components. I'm trying to figure out a work around. you can not change the maped pin in the Fuel pump set up page. But if I put it to open loop pwm then I should see FP_duty > 0 any time the fuel pump should be running.

Then I can go into the programmable I/O page and setup an output that is triggered to turn on anytime FP_duty is greater than 0. That way it should hopefully match the on/off relay functionality of the FP control as a band aid fix.

it won't work as well, since it wont prime with key on and such.


just fix your mistakes!

I agree. The components are on order to rebuild the circuit. I was still curious to try a work around re maping while I wait on those.

Wouldn't a variable speed fuel pump also prime at key on. So wouldn't it have a DC > 0 when it primes and trigger my stock FP relay properly?

what'd you need to order? you have a spare component for each thing on that circuit iirc.

look under the board and make sure your soldering to the transistors Q2 and Q19 are good -- no bridged pins.

Probe each point in the circuit.

I should have had a spare of each. But the first time around I built the entire board following the MS3x guide (not frank's writeup). I then troubleshooted a wiring issue since I read the harness pinout wrong. During the troubleshooting I removed every single non needed component from the board so I basically destroyed the spares that I should have had.

Much learning from this project. I'm just glad it's running my engine now except for the FP issue. The end is in sight.

DIY shipped out my order last night so I should be able to rebuild it mid next week.

No solder bridges on the two transistors.

So I gave the re-map "work around" a shot and it worked beautifully. Just in case someone else has a similar problem and stumbles upon this thread and wants to use the temporary band aid solution.

I used the VVT output pin and on the programable I/O page set it to on when FP_duty > 1.

The fuel pump primes on key on like it should and everything works perfectly.