Injectors wont fire?

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3.0trd

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Jun 13, 2008
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I believe i may have a unique problem. Just rebuilt my 89 n/a but it wont star. I checked spark, all good. I have fuel pressure, new gas, and good flow to the fuel rail.
injectors ohmed perfect at 13.8, and i have continuity at the injector clip while cranking. I tried plugging in an old injector, and they dont pop or anything. I have fuel pressure, but checked all the relays and everything is fine. They are green top injectors so they are high impedance( hence the 13.8 ohm resistance per the tsrm) im not sure where to go next?
 
Nick M

Nick M

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The power is constant (through circuit protection), ground is supplied by the PCM when the conditions are met to fire. You are not as straight as you think if none of the injectors fire but there is power to them.
 
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3.0trd

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Jun 13, 2008
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I just did a noise and touch test on the injectors. plugged in an old one to get a better feel on it, and nothing. I have checked every relay and all sensors (tps, afm, main relay, circuit opening relay) fuel pressure is also fine. checking the tsrm at the moment to find a better way to check power and ground to injectors.
 
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3.0trd

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Jun 13, 2008
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ok, so the injectors have power at the ecu. perfect resistance on the injectors themselves. I don't know what I'm missing...
someone told me to check for continuity to the injector clip while cranking, and turns out I don't. any other test I should try at the injector itself?
 
Nick M

Nick M

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For all I know, your injectors are firing and the engine is out of time. You think we have a crystal ball and can see what you are doing?
 
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3.0trd

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Jun 13, 2008
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Not at all. I know what i am doing mechanically. Its wiring and electrical i need help with. I checked physical timing twice and left the upper cover off. Distributor is pointing perfect at number one at tdc. Ive double checked all my wiring connections, checked spark, i have good fuel pressure, tested all the sensors and relays that i know have something to do with the fuel and ignition, no stored codes, and it will try to start with carb cleaner.
As far as i can see it is just my injectors that seem to be inop. I have followed thr tsrm for all the checks that i have performed, and im not sure what i could try next. Im not sure what i should be seeing at the injector plug to get a better idea of where to go next
 
3p141592654

3p141592654

90T
Oct 11, 2005
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In post 1 you say that the ignition is good. How did you test that?

In Post 5 you say that the injectors have power at the ecu. You mean that there is 12V on the #10, #20 and #30 pins at the ecu?
 
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3.0trd

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Jun 13, 2008
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I have spark at the distributor, and the plug wires, and then grounded a spark plug and got it to jump the gap.
As for the injectors, yes, i mean i have power at the # 10, 20,and 30 pins with the key on, while back-probing the connector
 
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3.0trd

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Jun 13, 2008
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I checked spark coming from the coil, at the end of the wire to the plug, and then grounded a plug and saw it jump the gap. I also did resistance tests of the plug wires, primary and secondary coil, and pick up coils, per the tsrm. everything there was within spec.

as for the injectors, yes, I mean I have power with the key on at the number 10, 20, and 30 pins while backprobing to e01 and eo2.
 
3p141592654

3p141592654

90T
Oct 11, 2005
3,816
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Thousand Oaks, CA
Spark, with no injectors, 12V on injection circuit to ECU, and no codes is highly unusual. A bad Igf signal might cause those symptoms, but that sets a code. A bad NE signal from distributor would not produce a spark or injection. Could be a bad ECU but that is very rare.

If it was me, I would confirm no injection through an electrical test.
 
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3.0trd

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Jun 13, 2008
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this is exactly what has me baffled. so how do I go about the electrical test for injection? I'm going to do another spark test right now just to make sure, then check for codes again.

ok, still have spark and still no codes...
 
Nick M

Nick M

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3.0trd;1931691 said:
i mean i have power at the # 10, 20,and 30 pins with the key on, while back-probing the connector
Click to expand...

Then the ECU has determined the conditions to ground the injectors has not been met.
 
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3

3.0trd

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Jun 13, 2008
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Tracy
injector grounds are clean and tight. I even tried hooking a piece of wire straight from the strap to the neg. terminal of the battery. I got ahold of a noid light set today, just to be positive. it failed, but I do have battery voltage to both sides of the injector clip with the key on, so at least I know its a grounding problem. leads back to the pcm not getting a signal it needs.
 
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3.0trd

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Jun 13, 2008
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well my friends, flame away. I solved the puzzle. as I was rebuilding my motor, I had my wiring harness laid out in my driveway one day. my girlfriend comes home and runs over the distributor plug... wires and pins are all ok, just the connector damaged. look up the wiring diagram in my Haynes manual, and put the wires in order of what I saw, when that didnt work, I flipped them, knowing that it was one way or the other. still nothing... it wasnt until I was on the TSRM checking resistance at the distributor that I realized the pins were labeled different (ne,g, g1, g2) that I realized my haynes manual doesn't show the correct order that the wires go in... put them in correct order and low and behold, she is alive! again, flame away, but thank you for the assistance!
 
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