MPGuino in CRX

[brucepick]

The MPGuino needs an injector "signal" from the injector's ground wire.
Reason is, the positive wire is always hot and the ground is switched by the computer to control injector pulses.

On my '97 Civic I hooked mine up at one of the injectors. Doesn't matter which one. Check for voltage in the two injector wires with ign switch in "run" position, and use the wire that has no voltage. That's the switched ground. Yes you also could find that wire at the computer harness but I was more comfortable tapping into it at the injector.

Good luck with it - super project! Project thread, in case you haven't stumbled on it:
http://ecomodder.com/forum/showthrea...crx-17565.html

[wyatta4]

I hooked it up to the ground wire on this injector
(last on the left)


Onto this ground wire from that injector


And when I start it up that injector misses completely..

This whole MPGuino is starting to piss me off a bit.. I've spent hours on the case for it and it looks terrible and I can't even figure out how to wire it up right.
But hey, at least it powers on right.

Thanks for the help so far btw. I appreciate it.

[meelis11]

Did you try with other injector wire? How you connected pins to socket?
Did you find VSS signal?

Dont give up, this little thing is worth these few hours

edit: I googled "honda crx hf ecu pinout" and find this:


So probably you need one injector (example "INJ 1") and "speed pulser" wires (VSS)

[wyatta4]

So do I need to connect to the actual injector or or the ground for the injector?? I soldered the pins to my wire... Crappy job though. Best I could do. My VSS is mechanical.. Will it still work?

[nickdigger]

If i remember correctly, the Hondas keep the injectors high at 12v most of the time, then drop to GND to fire them. So, no, you don't want to mess with the GND wire of the injector. You want to tap into, as meelis suggested, INJ 1 (pin A1 on the ecu). The mpguino will then see the 12v get pulled down to 0v during the injection.

When you say your VSS is mechanical, do you mean you have a mechanical speedo cable spinning inside your gauge cluster? Even if you do, there may still be a high-low electrical signal coming out of the cluster, for use by the cruise control. Hopefully your B18/B19 "speed pulser" is the speed of the wheels, not "engine speed" (aka Tach).

[wyatta4]

Okay. I tapped into the injector one. Now my car is idling strange and the check engine light is on.

Yeah it goes from the cluster to the tranny and is mechanical, spinning..

[wyatta4]

This is rediculous. I capped off my spliced end and it's still running like crap, dying and the check engine light is on! This MPGuino is screwing up my car

[meelis11]

Can you read this code somehow? Maybe you touched or disconnected some other things when you did this mpguino installation? You could try to remove one wire from battery for a few minutes - so car ECU resets and clears errors.
I have hard to believe that mpguino can disturb car and ECU if installed properly.

[wyatta4]

I did remove the negative terminal for a few minutes and it didn't clear. I'm sure it's the way I've installed it but I just can't be trying to wire it up every night only to have my injectors miss and not be able to drive it the next day.

I hooked into a constant power, with a 10 amp fuse, I used a ground, I took the pin out of injector 1 spot and soldered the injector feed on to that and put it back in the pin slot perfectly. I capped off the VSS line and left that alone since I don't know where to connect that, started the car up and the injector was missing completely. It would randomly die too. Now it still misses and I can't get rid of the injector codes and I think an electrical load code. Check engine light is still on.

I'm not saying its the MPGuinos fault, but I didn't think it would be this difficult to get it working.

[msc]

This link should give all the details you need for hooking up the MPGuino. CRX Community Forum • View topic - MPGuino

My best advise on wiring mods is to never touch the stock wiring under the hood unless there is no alternative. Your splice at the injector is a major long term reliability problem that will eventually fail. It's much better and easier to make the splices at the ECU.

I read your build thread and have a couple comments.

If your fuel line splice is on the low pressure return line it would probably only become a problem during an accident. If the splice is on the high pressure supply line it's incredibly dangerous and should be fixed properly before further driving.

For your interior restoration keep in mind the HF did not come with a cargo divider to save weight. The back end is mostly open on the stock HF.

You mentioned buying an OEM muffler for $75. Is that a genuine Honda OEM muffler for an HF or is that something else like an OE replacement muffler or DX muffler?

Mike