Have been searching main relay diagrams for days on multiple forums and have not been about to find out which pin on the main relay in a dpfi system sends power to the injectors. Anyone know or have a diagram? I know what pin sends power to the ecu, fuel pump, whats ground, pretty much everything but what I need to know. A bit frustrated and simply not getting power to my injectors.

 

http://lmgtfy.com/?q=honda+main+relay+wiring

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It's PIN 3




Are you running an injector resistor box?
Is there power at the resistor box?

 

I appreciate the reply, it says to ecu though? I read that on dpfi main relays the pin that sends power to injectors only does that and nothing else? I don't really want to pull my main harness back and pull plug C313 through the firewall but it looks like I'll have to do it that way and trace the two power wires.

 

Ah - totally missed the DPFI in your first post.

The wire is Yellow/Black

 

Thank you very much for the diagram. It simply comes off pin 5 in line with the fuel pump? What is the dot that I believe says S440? Is that simply a splice? Cause it isn't a connector.

Damn, was about to give you rep but they don't have rep points on here, lol

 

I wouldn't go by Pin 5.
I would look for the wire color in the harness.
The relay pin out may be different than what the numbering scheme is on the diagram.
I would assume it's a splice seeing how the two injectors both have splices that lead into two ECU pins.
They are also denoted with the "SXXX"

 

Yeah its looking like pin 7 is for my fuel pump as it only has power while pump is priming and that pin 3 is for my injectors.

So it looks as there is trouble in the wiring between main relay and the injectors but that pin also runs to the ecu. Thinking about running new power wires from relay to ecu and injectors. Good idea?

Pin 3 is also yel/black just like the injector power wires as pin 5 is black/yel

 

So just doing a checklist
-power at pin 3 of main relay but no power to plug C313 for injector wires
-zero blown fuses.
-all grounds are solid.
-fuel pump primes and turns off after 2 seconds and I'm getting all clicks from the main relay.
-After the 2nd main relay click my check engine light turns off but then quickly turns back on. < My only other lead but I've seen that it can mean many things.

Other info

0BD-1 D15B
P28
Dx converted engine harness.

Background
-Was running fine for months, had an injector that was losing ground signal and would stop working then kick back on then stop again so I decided to pull my engine harness and clean it up and tuck it. I am certain that I have done everything correctly and only extended a few wires and tucked a bit of it/ re-wrapped it.

 

Is the blue/wht wire from fuse 2 (10 amp) the only power wire to the ecu? Or the wire that "powers" the ecu? I'm just wanting to make sure I have good power to the ecu. I have good grounds.

 

I am getting 12v to pins A13 and A15 from pin 3 of the main relay. So the main relay sends 12v to the ecu to these pins which are also going to the injectors?

 

You lost me.

This is how it actually works -
The injectors have constant power.
The ECU sends ground pulses.

We on the same page?
It seems like you are saying that the ECU sends the +12v, but it doesn't.

 

Yeah we're on the same page, lol. Im just seeing two yel/black wires at the ecu pins A13/A15. Wondering what pins the ecu gets its 12volts for power from. I mean, the ecu has to get power from somewhere.

The weird thing is I have no power to the engine harness plug C313 for my injector wires but the fuel pump is priming strong. And now the CEL does turn off on the 2nd main relay click but comes back on in less than a second.

I really appreciate you helping me 4drEF. You're the only one who has and out of anyone in my area I know the most about Honda's wiring so when Im stumped and google utterly fails me Im **** outta luck, lol. I do have a PDF haynes that Im looking at as well though.

 

Bump and main question. What could be causing my CEL to come back on less than a second after it turns off when the fuel pump is done priming? I've seen it stay on but never turn off then come right back. Stumped as relay is working fine and everything to do with it is golden except no power to injectors, or even to the driver-side engine harness plug pins for injectors.

 

a bit "off-topic" maybe, just got one question i have error code 16 on my dohc zc and it sometimes runs on 3 cylinder and sometimes 4, which makes me think that its a injector that glitches somewhere. Could the main-relay cause error code 16 and make the car runs this way?

 

Lol, not off topic but thread jacking yes. I don't mid though. Check for 12v on all yellow wires at injectors. If you have 12v at all yellow/black wires then check pins on ecu plug A for injector signal (ground). Find which injector and if its not getting signal try running a new signal wire from ecu pin to injector. Best of luck, and code 16 is a general injector fault code, could be anything from not enough fuel pressure, to no voltage, to what I described as losing signal from ecu which sounds right in your case unless one injector is just shitting out on you.

 

oh ok thanks!

 

The ECU gets power from the main relay.
So does your injectors and fuel pump.

considering that your fuel pump is priming, then your injectors should also be getting power.
My approach would be to check the wiring from the main relay to the injectors.
First stop would be at the firewall connector, C313.

Since you already checked that, and no power is present, then try jumper wire from main relay to injectors just to verify.
If that works, then there is a break in your cabin harness wiring.

 

Injectors now have power and signal, plenty of fuel and spark. Not messing with it anymore tonight but here is a video of how it sounds when cranking. Battery also has 12v and is new. It just sounds weird as hell and I know mechanical timing is good and has compression. Seriously a 60k mile motor with a new timing belt a few months ago all done how it should be.

http://www.youtube.com/watch?v=1v6cLR2U_Dc

 

I know you don't want to hear this, but that's a hella-clean install. It looks damn good. I just wish it was working for you. That crank sounds absolutely nothing like a Honda.

 

Thanks for the compliment! I wish it was too! The crank is what throws me off. It sounds so, so,..weak and I don't even know. Just terrible. I have good grounds a charged battery. Only things to go off of are weird cranking and the CEL coming back on.

Going to double verify spark at every cyl and fuel in the latter morning.
I know that my mech. timing couldn't have skipped a tooth, tension is perfect.
Anyone heard their car crank like this?

 

Sounds like it's spinning loose - as in no resistance.
Even after you have stopped turning the starter, it sounds like the motor free spins for a second.
Check compression.

 

I agree, that is what it sounds like. :[ How would I lose compression during the time that its sat for about a month, dry rings? It had comp before, just injector issue. This car is kind of a headace but I love it, lol. Going to do a comp check right meow.

 

This is the weirdest **** I've ever encountered with anything automobile related. Had barely any compression. Poured a little oil in the cyl's and it gradually started to sound better then it fired up. Seems to be running good as ever except I have no tach signal. So yeah, weird as ****, only sat for a month.

 

Have yet to check compression after I got her fired up but after driving it around today seems to run just as good as it always has. No smoke or anything. Only when it first fired as I had poured a quarter cap full of oil in each cyl. I guess the cylinders just got dry?

Going to do an oil change just in case though as I tried to get it to fire for a bit and probably have some fuel in my oil. Thank you for all your help 4drEF! I hope this helps someone else as well one day!