86 4runner fuel injector will not fire
10-24-2009, 08:09 AM
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86 4runner fuel injector will not fire
im new to these forums, so bare with me, hope im in the correct one. fuel injector harness test good, shorted blue wires for #2 and #4 tootransistor plug and all i good, but #4 still wont fire, but got spark at plug, need some help, getting frustated
10-24-2009, 08:20 AM
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Grab an ohmmeter and check the injector resistance. can't tell you what the reading should be but you can compare it to the resistance of the other injectors. If it's open or differs from the other injectors by more than a few ohms the injector is probably bad.
10-24-2009, 09:39 AM
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ty for the info, but ive moved #2 injector plug too #4 and made #4 start working, leading me to believe it it was in the harness, but thats good, thinking it may be the comp now?
10-24-2009, 10:17 AM
#4
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On my V6 3VZE the manual shows that the groups of injectors for cylinders 1,3,5, and 2.4,6 all get turned on at the same time. One wire out of the ECU for each group. It points to the injector harness at cylinder 2, since you said you tried it at #4 and it worked there.
10-24-2009, 10:29 AM
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arent the only wires from comp the 2 grounds, the power wire come from the transistor mounted on the fire wall, i think, i reckon that could be bad,but i have continuity on both blue wires, one for #2 and one for #4 at the transistor plug, am i looking to deep into this, or do just not gett it
10-24-2009, 11:43 AM
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as he said- the 22re's are almost the same way. Actually the power wire comes from the ignition to the injector resistor, (if so equipped as ur truck has) that's 1 wire. then 2 wires out to the injectors.. they are batch fired so #1 and 2 should open at once and #3 and 4 should open at another time. there are 2 wires that go from the injectors TO the ECU. The ECU grounds out the connections when told to fire each set of injectors... First I'd plug a noid light in each injector plug and see what happens. that should give an indication if eveything in the wiring harness and ecu is ok or not. If one ore more doesn't flash, when u turn the truck over, break out the voltmeter and see where u loose voltage in that circut by checking it to ground.
Last edited by jimep; 10-24-2009 at 11:52 AM.
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10-24-2009, 11:44 AM
#8
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You should probably check out an electrical diagram for your vehicle. On mine, like yours, the grounds come from the ECU, but the power comes directly from the ignition switch. You may have a resistor pack on your firewall, or not. You might be able to open it up and check it out with an ohmeter.
10-24-2009, 11:53 AM
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Courtesy of 4Crawler:
Not reflected in the diagram is that the ECU holds the wires at +12v until it's time to fire the injectors at which time it switches its wires to ground during the injector firing event. Meaning that if you plug a voltmeter into each terminal of each injector plug, they should read 12v to ground with the key on. If it doesn't, it's likely an issue between the plug and the splice in the harness since #2 does fire but #4 doesn't.
Not reflected in the diagram is that the ECU holds the wires at +12v until it's time to fire the injectors at which time it switches its wires to ground during the injector firing event. Meaning that if you plug a voltmeter into each terminal of each injector plug, they should read 12v to ground with the key on. If it doesn't, it's likely an issue between the plug and the splice in the harness since #2 does fire but #4 doesn't.
Last edited by abecedarian; 10-24-2009 at 11:59 AM.
10-24-2009, 11:58 AM
#10
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So if the power from the resistor pack is split into two for your #2 and #4, and #4 works, then something has to be wrong with the harness one one side or the other.
10-24-2009, 12:01 PM
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ok, im not thinking the right way, ive got one blue wire from resistor that t's, to #2 and #4, so in a nut shell thats the same wire, and #2 works but #4 doesnt and they are all good, so i think im comprehending that yall are saying that the pulse for #4 isnt getting there?and if not, that i should look at either the resistor itself or the ecu, im trying to figure it out guys, little slow though
10-24-2009, 12:06 PM
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Yeah, you beat me to it. 
But although you are correct that the injectors are batch fired, all 4 fire at the same time, for the same duration, once per engine revolution.
So, like I said, if #2 injector plug fires an injector but #4 doesn't, it's a wiring issue, either the splices, the #4 plug or the wires between the splices and the plug.
But although you are correct that the injectors are batch fired, all 4 fire at the same time, for the same duration, once per engine revolution.
So, like I said, if #2 injector plug fires an injector but #4 doesn't, it's a wiring issue, either the splices, the #4 plug or the wires between the splices and the plug.
10-24-2009, 12:09 PM
#15
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Yeah, you beat me to it.
But although you are correct that the injectors are batch fired, all 4 fire at the same time, for the same duration, once per engine revolution.
So, like I said, if #2 injector plug fires an injector but #4 doesn't, it's a wiring issue, either the splices, the #4 plug or the wires between the splices and the plug.
But although you are correct that the injectors are batch fired, all 4 fire at the same time, for the same duration, once per engine revolution.
So, like I said, if #2 injector plug fires an injector but #4 doesn't, it's a wiring issue, either the splices, the #4 plug or the wires between the splices and the plug.
10-26-2009, 03:47 AM
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hey, i got it. THANKS for the input guys, the metal terminal in the plug was split in two, everytime i pulled plug off to test the terminal would go back together, thus giving a good test, when i put it back on injector, it would open up, thus not making contact, bought new pigtail from autozone and runs like a champ
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