Spark but no injector fire, 2jz (7m harness/ecu)

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#1
Hey all, new to the forum but not new to supras, hoping someone could give me a nudge in the right direction or maybe point out so ething I'm missing.
I have a 79 Datsun 210, stuffed a 2jzge in it, using 7mgte electronics. Had it running and driving but tore it down to do some other work to the car. It's back together again, but now has no injector pulse. Has spark.
I've dealt with this issue in The past with other cars and I've gone about all the usual things that would cause it, ecu grounds, ignitor, cps, checked for voltage, ecu turns on/has voltage, 12v at injectors, sensors all have voltage when applicable, ohmed out and voltage dropped the injector wiring, ohmed out the CPS wiring, really can't find a reason why this thing should not run...
Anyway any ideas or suggestions would be welcome.
Thanks
Josh
 

plaaya69

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#2
I know there is multiple wires for the ECU ground and those are very important so that would be my starting point.

Are you running a fuel injector resistor?
 
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#3
Yeah, running injector resistor, and it seems to be functioning, there's 12v at the injector.
For ecu grounds they are all grounded to the intake manifold, which is a verified good ground.
As far as testing the CPS outputs at the wcu while cranking, what signal am I looking for? Can this be done with an ohmeter or are we talking oscilloscope? I've resistance tested the different cps's/dizzys I've tried but would like to actually see the signals at the ecu connector
 

3p141592654

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#4
If you have spark the CPS is good. Do you get any codes set?

I would check for continuity on the injector circuits #10, #20, #30 from injector to ECU plug, although the chances of all 3 going bad seem low.

The other test would be to manually ground the injector circuits (#10, etc) and confirm injector operation.
 
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#5
Yeah I ohmed out the 3 injector grounds between injector and ecu and they're good. Also with them unplugged the injector test circuit reads battery voltage on each side, which works as a voltage drop test, same voltage on each side of injector with it unplugged. Issue is that the ecu is not grounding them.
That's not a bad idea though, just to verify, manually grounding the injector at the ecu plug, with a noid light in place, should light up. Like I said I already ohmd and volted the grounds from injector to ecu but extra peace of mind is always good.
 
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#7
So I backprobed the ecu earlier today and looked at the signals from the CPS, showed some slight voltage jump while cranking, but I'm assuming you can't see the actual voltage spike without an oscilloscope?
 
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#9
So looking into other things, I read that if the igf signal to the ecu from the ignitor is bad or delayed it can cause the injectors to not fire? Would I still have spark? I think it is going to come down to a broken wire somewhere and the CPS/injector wiring has checked out, grounds are good, power to ecm/injectors is checked off. I tried swapping ignitors already, the only other thing I can possibly think to check is this igf signal
 

3p141592654

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#10
You will set a code 14 if there is no IGF signal. I would go ahead and check codes. But bear in mind that if you are seeing a spark, that's a pretty good indication the ignition system is ok. And code 14 takes a little while to set, so o you should see some attempts to fire first.


Note that codes get erased if you cut battery power to the ECU.
 
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#14
So if I tied sta into the solenoid wire then I could then get codes pertaining to "no signal from yada yada within x engine cycles" ?
 
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#16
Ran a wire between STA and the solenoid wire, then cranked it a bunch, pulled codes. Only code was 32, which is hac sensor....
 
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#18
I'm trying to figure out a scenario where it has spark but no injector pulse, injector grounds are good, tested several different ways, ecu group d's are good, tested several different ways, power to injectors etc
 
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#20
Yeah, the problem is no injector ground pulse from ecu. Fuel pump is on a switch, 12v relayed, gauge installed into the rail permanently, that reads 45 or 50 psi I forget the actual pressure
 

RacerXJ220

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#21
Of course, just going over the basics I didn't see listed. Wish I knew more to then help. Looks like a very nice build.
 

3p141592654

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#23
I'm trying to figure out a scenario where it has spark but no injector pulse, injector grounds are good, tested several different ways, ecu group d's are good, tested several different ways, power to injectors etc
So getting down to the basics, is injection done off the cam sensors signals vs spark being off the crank sensor?
The CPS does the job of both cam and crank sensors on a more modern setup. The Gx signals sync to TDC #1 and the NE signal is the crank position variable with 15 degree accuracy.

The only scenarios that cut fuel are accompanied with codes that you are not seeing.

Let suppose for a minute that the injector 12V supply has high resistance, then you might see this behavior. Try putting a stoplamp in series with the 12V supply on any injector connector and connect the other lead of the stoplamp to ground. You should pull some decent current through the injector resistor pack.
 
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#24
Yeah i did that with a blinker, went 12v side to chassis and it lights up, also connected the 2 Injector pins and then grounded at the ecu, resulting in a light up. you're saying try it with specifically with a stop light for more electrical load? Thinking it could be possible for the resistor pack to be fucky and kind of work?
 

3p141592654

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#26
I think your test with a blinker is probably sufficient. We are looking for something that test out ok on a resitance test of a DVM, but fails on large currents or when it gets hot.

Was the blinker a turn signal bulb, or just a noid test light?

But if you grounded the injector lead at the ECU and the injectors clicked then I think you are good. That would be a full current test. Would be good to verify it actually sprayed, but a click is almost as good.