# 3 injector double pulsing - JeepForum.com
 
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post #1 of 15 Old 09-17-2009, 03:09 PM Thread Starter
WaldosYJ
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# 3 injector double pulsing

Here I go, I have delt with this for almost 1 year and have narrowed down my problem to the #3 injector occasionally giving a double pulse (maybe the 6th or 7th time through the order it will do it twice in a row and then be ok for 6 or 7 more rotations and then do it again). just wondering besides the computer what it could be, I will cross my fingers.

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post #2 of 15 Old 09-20-2009, 11:16 AM Thread Starter
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Any ideas anyone.
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post #3 of 15 Old 09-20-2009, 11:20 AM
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Sorry I can't help you out but it might be easier for others to help if you fill out your jeep profile information or at least let us know what engine you're talking about.

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post #4 of 15 Old 09-20-2009, 11:33 AM
idaholtby
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Each injector has power supplied all the time and the ecm controls the pulse by supplying a ground signal. I suppose the ground(signal) wire for the injector cold be shorting to ground somewhere. Just how do you know that the #3 injector is doing that? You could try swapping injectors with another cylinder and see if it moves. If not, then you could swap injector wires at the injector and swap the pins accordingly at the ecm connector to see if it moves. If you swap the wiring and injector and the problem remains with the #3 cylinder, then the problem would have to be the ecm.
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post #5 of 15 Old 09-20-2009, 05:08 PM
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Quote:
Originally Posted by WaldosYJ View Post
Here I go, I have delt with this for almost 1 year and have narrowed down my problem to the #3 injector occasionally giving a double pulse (maybe the 6th or 7th time through the order it will do it twice in a row and then be ok for 6 or 7 more rotations and then do it again). just wondering besides the computer what it could be, I will cross my fingers.
How are you testing for this?
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post #6 of 15 Old 09-20-2009, 07:00 PM
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you can use a test light
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post #7 of 15 Old 09-20-2009, 07:24 PM
idaholtby
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Originally Posted by Plato2k5 View Post
you can use a test light
It is not how can you, but rather.. how did he. We are just curious as to how this was determined and even... how is the rig running? Is it running rich that led to this diagnosis?
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post #8 of 15 Old 09-20-2009, 07:48 PM
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Ah yes lol. I would imagine you would feel it under acceleration
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post #9 of 15 Old 09-20-2009, 09:00 PM Thread Starter
WaldosYJ
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Thanks guys for the help. 2.5 liter raging 4 banger. The symptoms were a pour idle, would putter like lack of fuel for a second and the idle out. Under acceleration it would feel like a miss but not every time just about 3-4 seconds apart. Checked fuel pressure with and with out regulator all #s were right on so went to the injectors pulled fuel rail and cranked to watch order and spray pattern everything seemed good. Decided to pick up noid light at parts store just to save gas from going allover garage and to check pulse of injector. Noticed on the # 3 injector that every 6-7 time through it would skip #4 and spray the #3 instead, it does this twice in a row and then go back to normal for 6 - 7 more sequences and then happen again. Hope I explained it well. If not just keep asking me questions. Thank again for the help.
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post #10 of 15 Old 09-20-2009, 09:37 PM
Plato2k5
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Very good suggestion here. I would start with this and than report back with what you find.

Quote:
Originally Posted by idaholtby View Post
Each injector has power supplied all the time and the ecm controls the pulse by supplying a ground signal. I suppose the ground(signal) wire for the injector cold be shorting to ground somewhere. Just how do you know that the #3 injector is doing that? You could try swapping injectors with another cylinder and see if it moves. If not, then you could swap injector wires at the injector and swap the pins accordingly at the ecm connector to see if it moves. If you swap the wiring and injector and the problem remains with the #3 cylinder, then the problem would have to be the ecm.
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post #11 of 15 Old 09-21-2009, 05:05 AM
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In addition to the above suggestion, I would also look at unwrapping the injector harness to check for any insulation cracks, chafed insulation, or any other way you could end up with "cross-talk" between two injector wires. Look real close where the wires for 3 & 4 lie in close proximity & check all the ground connections.
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post #12 of 15 Old 09-21-2009, 06:52 AM
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One thing to is check the mechanical parts of the timing system. Timing chain play, distributor setting, cam the distributor gear play. If any of the above is bouncy (loose) then it could cause the wrong signal to be seen too.
Plus check the wiring close from the injector all the way to inside the connector for the ECM. The protective hood on the connector at the ECM does come off and the pins for number 3 and 4 injector are side by side.

A 89 yj with a 4.0 aw4 sye out of an 92xj. Now the hard part is done time to get it up in the air just a bit. Working on 8.8 with 3.73 and lsd for the rear. and new D30 hp with 3.73 .
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post #13 of 15 Old 09-21-2009, 12:30 PM Thread Starter
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I will try everything an report back thanks to all.
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post #14 of 15 Old 09-21-2009, 12:40 PM
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After post #9 post #11 seems the most likely answer, might want to undo the ECM connector and check for moisture or corrosion to rule this out first.
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post #15 of 15 Old 10-03-2009, 06:18 PM Thread Starter
WaldosYJ
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sorry this took so long was away getting hitched. back to everyday life and working on my jeep the more enjoyable part of the day. Checked Harness for moisture dry as a whistle, no crud build up. Traced #3 and #4 injector wires found no breaks or wear anywhere even close at the harness. Checked Continuity for #3 and #4 wires all carry current and could not get any cross talk between wires so no breaks that i couldnt see. Ok timming or ecu? the only question that leads me towards the ecu is that if the timming chain is streached and messing with the injector pulse wouldnt it still fire on #4? when it messes up it fires 1-3-3-2-1-3-3-2 then goes back to 1-3-4-2-1-3-4-2. Just checking befor i go tearing into fan shroud fan ect. just to check something that i could have negated from the begining? Thanks again for all the help, this is the best forum with the greatest people.
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