injectors not firing, how come?

[JNM240]

Background: still finishing up swapping my CA18det into my 90 S13 coupe. Wired it up by heavythrottle.com's writeup (verified numerous times by me, and 2 friends), and checked with FRSport's writeup as well. Car has fuel pressure, cranks (spins over quite nicely), has spark (felt that up to my elbow), and it turns over but wont catch.

So ive traced the ignition wiring from the coil packs all the way back to the ECU and everything is fine. Then i start probing the injectors while its turning over. Nothing. So i probe pins 101, 110, 103 and 112 of the ECU (injectors 1,2,3 & 4 respectively) and get nothing. What tells the ECU to fire the injectors? Ive pulled the CAS and turned it by hand while the key is on and i hear a relay click when it starts and again when it stops, so im assuming this works. MAF wires have been verified. I just get no signal from the ECU to the injectors.

Anyone have any ideas??

Jason

[boost_boy]

Background: still finishing up swapping my CA18det into my 90 S13 coupe. Wired it up by heavythrottle.com's writeup (verified numerous times by me, and 2 friends), and checked with FRSport's writeup as well. Car has fuel pressure, cranks (spins over quite nicely), has spark (felt that up to my elbow), and it turns over but wont catch.

So ive traced the ignition wiring from the coil packs all the way back to the ECU and everything is fine. Then i start probing the injectors while its turning over. Nothing. So i probe pins 101, 110, 103 and 112 of the ECU (injectors 1,2,3 & 4 respectively) and get nothing. What tells the ECU to fire the injectors? Ive pulled the CAS and turned it by hand while the key is on and i hear a relay click when it starts and again when it stops, so im assuming this works. MAF wires have been verified. I just get no signal from the ECU to the injectors.

Anyone have any ideas??

Jason

Is your injector resistor hooked-up?

Are all wires from your engine harness grounded?

Do the terminals at your injector plugs show voltage?

Are your fuel lines hooked-up correctly?

Answer these questions and I'll do my best to help you with your dilemma.

Dee

[trevr]

Have you check the igniter, mine had similar issue, but only one cylinder wasn't not firing.

[boost_boy]

Have you check the igniter, mine had similar issue, but only one cylinder wasn't not firing.

The ignitor doesn't control the fuel injectors. Since he's getting spark, the ignitor appears to be functioning because without the ignitor, there won't be any spark.

Dee

[JNM240]

Is your injector resistor hooked-up?

Are all wires from your engine harness grounded?

Do the terminals at your injector plugs show voltage?

Are your fuel lines hooked-up correctly?

Answer these questions and I'll do my best to help you with your dilemma.

Dee

Where do i find the injector resistor? I see in the FSM a dropping resistor, but either my harness didnt come with one, or i am completely overlooking it.

Yes, all wires from the engine harness are grounded, per Heavythrottle.coms SR wiring instructions.

No, the terminals at the plugs show no voltage at all, nor do they trigger my test light, either cranking or otherwise.

Yes, fuel line comes into fuel filter, through fuel pressure gauge sending unit, to rail, out rail, through pressure regulator, to return line. And if i leave the key on long enough with the pump running, some fuel seems to leak past the injectors and it 'almost' catches for a second. But after that it continues to crank and not start. Ive even cranked it without the #1 plug in and got no fuel in the cylinder. So the injectors are definately not firing.

I even recently purchased another ignitor (before i learned how to test my other). Its definately not spark related. I picked up a voltage meter today too, and that shows me im still getting nothing at the injector plugs, nor from the ECU pins that fire the injectors. So somewhere, something isnt telling the ECU to fire the injectors. But the coil packs are firing just fine (shocked the living crap out of me testing it while my friend was cranking it).

Timing has to be dead on too, at least cam to crank timing. Ive moved the CAS forward and back between cranks and nothing changes.

I do have Venom 550cc injectors installed, and currently have the stock EPROM installed, but regardless, im still not getting signal at the injector plugs. And yes, ive socketed the ECU already and have written a tune for the 550cc's, im just using the stock EPROM to elimanate my tune as a reason for the no start.

Thanks for reading this and all the help so far, Dee. I love this motor and know its going to be a badass. Its just right now i feel like im banging my head against a wall.

Jason

[TD or Not TD]

if you do not have the resistor at all then that is your problem.

go to yahoo.com and do a search under images and type in "injector resistor" the first 4-5 pictures are very close to what you need. the nissan one is a little longer but youll get the idea. i had one in my harness but it was getting no power to the center wire. once i did that the car got fuel and fired up.

good luck!

[float_6969]

Yea, you're either missing the resistor pack, or you've got a euro-spec harness, and it lacks the plug for the resistor pack because it's on the BODY harness.

You should have a plug on the harness that has 5 wires going to it that connects to nothing. It was originally near the igniter IIRC.

The resistor pack looks like and odd silver sort of rectangle shaped box with 5 wire and a plug coming out of it.

If you don't have this, or it's not wired up, no power ever makes it to the injectors and so they can't open.

Also, in-case you didn't know how it worked, the injectors are provided 12V+ at one side and then the ECU provides a path to ground. So unless you have a very fast reacting multimeter and you had it set to continuity, and you were testing through the injector plug, through the ECU, to ground, you wouldn't have gotten a signal. And even then I doubt you'd pick it up as at starting, the signal is very brief.

[JNM240]

Wow, float, that is an amazing explanation. That would explain why i wasnt seeing anything at the ECU pins for the injectors.

You wouldnt know the color of the wires on this resistor plug, would you? There is a plug that the ignitor 'could' plug into (6 pin) but it doesnt have the 4 pin plug (output) nearby. Its kinda up by the original MAF plug and doesnt connect to anything. In the morning, ill go see what colors the wires are.

So, if i go get a DSM dropping resistor, i just wire it up to this plug and everything should be hunky dory? Or should i try and locate an OE Nissan one that still has the plug on it?

BTW, thanks a MILLION for the explanations. You wouldnt believe how much ive been stressed out over this. Had today (wednesday) and tomorrow (thanksgiving) off and really really wanted to get her running for Friday. Even tho it looks like i hafta order a resistor, at least my mind is being put to ease that this might be the problem. Thank you Dee!! Thank you float!!! Thank you TD!!!!

[float_6969]

Now that I'm thinking more about it (I don't have a factory harness in my car anymore) think its a 6 pin plug, but it's only got 5 wires going to it.

The DSM one works fine, or you can try and get a Nissan one as well. They don't wear out very often as long as they are heat sinked well.

There is a write up in the stickies on how to wire up a DSM resistor pack. I think they're cheaper as well. If you don't want to wait, I think you can go to Radio Shack and get the correct resistors as well, but you'll have to build a plate for them to sit on that goes against the body, as they get quite warm.

[float_6969]

It is a 6 pin plug, but only 5 wires are used.

They are as follows:Color..........PurposeWhite........12V+ #1 InjectorYellow.......12V+ #2 InjectorGreen........12V+ #3 InjectorBlue...........12V+ #4 InjectorRed............12V+ from Battery (Ign. Switched)

BTW the striped wires of the sames base colors on each injector go back to the ECU and with the motor running are switched to ground.

IDK what the colors are on the Dropping Resistor side of the plug.

[JNM240]

So is this what im looking for??

http://cgi.ebay.com/ebaymotors...ZWD1V

[float_6969]

Yes. You might have to re-wire the engine harness to get it to work.

[boost_boy]

Dude, you had one on that motor. Either you got jacked for it or it's misplaced because I can definitely recall one being on there. If you need a DSM unit, just let me know. They work just as well if not better.

Dee

[ch187]

venom injectors eh? how much you pay for them?

[JNM240]

Dee, i know it didnt come with one. I removed the harness from the motor, but never anything off of the harness. When i saw the pic of the resistor in the FSM i thought for sure mine didnt need one since it didnt have one. But no worries, i have one coming now, and i see the plug its supposed to plug into.

ch187, iirc i paid like $275 back in May for them. I figured they should be ok with the stock T25 and let me boost it to max, then still be enough for a gt2871r down the road. And they are drop in replacements.