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Cylinder bank (1,3,5) not firing by TheRealShadowX
Started on: 08-04-2013 04:30 PM
Replies: 22 (798 views)
Last post by: phonedawgz on 08-10-2013 01:22 AM
TheRealShadowX
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Report this Post08-04-2013 04:30 PM Click Here to See the Profile for TheRealShadowXClick Here to Email TheRealShadowXSend a Private Message to TheRealShadowXEdit/Delete MessageReply w/QuoteDirect Link to This Post
Ok, 86 SE, 2.8 Auto.

What I know so far.

It's running on 3 cylinders, specifically the even ones. I am getting spark to all 6 cylinders. I have swapped the fuel rail and injectors for known good ones. No change. Checked the fuel injector harness wires, and plug. Appear fine. Checked connections at the ecm, look fine.

Checked both Inj fuses, both fine. Swapped them, no change.

Swapped out plugs and wires, no change.

This engine was just swapped in for a bad one, so I suspect wiring to the fuel injectors.

I'm sure I'm forgetting a bunch here, so feel free to add input.

Where should I be checking everything?

Fusible links?

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Gall757
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Report this Post08-04-2013 05:33 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Since the inj. fuses are set up for 1-3-5 or 2-4-6, there is something wrong with the wiring to that bank of injectors. Have you checked for power at the fuse box?
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Report this Post08-04-2013 05:49 PM Click Here to See the Profile for sleevePAPASend a Private Message to sleevePAPAEdit/Delete MessageReply w/QuoteDirect Link to This Post
Did the engine drop the bank at the same time, all of a sudden? Did you do some sort of work to the topend before this happend?

I would also check the 8pin connector(where the injector harness plugs into the main harness) for a loose connection. Also check for power there for each bank.
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TheRealShadowX
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Report this Post08-04-2013 06:31 PM Click Here to See the Profile for TheRealShadowXClick Here to Email TheRealShadowXSend a Private Message to TheRealShadowXEdit/Delete MessageReply w/QuoteDirect Link to This Post
Dropped the cradle to swap out.

Had 6cylinders on both engines before they were pulled. Now that the good engine is in it only runs on 2,4,6. I assume somethig isn't plugged in right regarding the injector harness. Just don't know where to check.

Haven't checked for power at the fuse box, no meter or tester with me tonight. :/
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trotterlg
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Report this Post08-04-2013 06:55 PM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
There is also a seperate fuse for each bank
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TheRealShadowX
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Report this Post08-04-2013 07:10 PM Click Here to See the Profile for TheRealShadowXClick Here to Email TheRealShadowXSend a Private Message to TheRealShadowXEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by trotterlg:

There is also a seperate fuse for each bank


I know, both are fine. Even swapped them for kicks, no change.
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phonedawgz
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Report this Post08-04-2013 07:30 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Use a long needle to backprobe the injection harness to engine harness connector.

Pink and Pink White should have +12v on them key on, engine on or off. If one doesn't then troubleshoot that problem.

The Lt. Green or Lt. Green/Black and Lt Blue or Lt. Blue'/Black should have +12v on them key on engine off. Starting the engine should reduce that voltage to about 9V One is for each bank.

If one isn't getting the voltage reduced to 9V, then the ECM isn't firing them, or the wiring between that plug and the ECM is bad.

These tests are to be preformed with the electrical connectors still plugged together.

[This message has been edited by phonedawgz (edited 08-04-2013).]

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TheRealShadowX
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Report this Post08-04-2013 10:37 PM Click Here to See the Profile for TheRealShadowXClick Here to Email TheRealShadowXSend a Private Message to TheRealShadowXEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by phonedawgz:

Use a long needle to backprobe the injection harness to engine harness connector.

Pink and Pink White should have +12v on them key on, engine on or off. If one doesn't then troubleshoot that problem.

The Lt. Green or Lt. Green/Black and Lt Blue or Lt. Blue'/Black should have +12v on them key on engine off. Starting the engine should reduce that voltage to about 9V One is for each bank.

If one isn't getting the voltage reduced to 9V, then the ECM isn't firing them, or the wiring between that plug and the ECM is bad.

These tests are to be preformed with the electrical connectors still plugged together.





Ok, so, Pink and Pink White, both have +12v, key on engine off.

Blue and Green have +12v, key on engine off.

Here's the kicker. Key on engine on BOTH still have +12v.... What gives?! Neither drops to 9v!

So... Neither bank should fire? Yet one is? Gaaaah...
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AL87
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Report this Post08-04-2013 10:52 PM Click Here to See the Profile for AL87Click Here to Email AL87Send a Private Message to AL87Edit/Delete MessageReply w/QuoteDirect Link to This Post
ever check the wiring connections going straight to the ecm?
a pin on mine burned out once... had to replace the ecm with a spare. after that, everything worked fine.
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TheRealShadowX
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Report this Post08-04-2013 10:55 PM Click Here to See the Profile for TheRealShadowXClick Here to Email TheRealShadowXSend a Private Message to TheRealShadowXEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by AL87:

ever check the wiring connections going straight to the ecm?
a pin on mine burned out once... had to replace the ecm with a spare. after that, everything worked fine.


ECM connections have been checked and look just fine. Plugs are secure and seem just fine.

I do have to wonder if maybe the ECM has gone bad somehow, though I can't imagine how.
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Report this Post08-05-2013 11:22 AM Click Here to See the Profile for FIEROFLYERSend a Private Message to FIEROFLYEREdit/Delete MessageReply w/QuoteDirect Link to This Post
A set of noid lights would let you know if the injectors are firing but the injectors are not that easy to get at on the 2.8. Could be the ECM as it is batch firing so if no ECM pulse to injectors no fuel to those cylinders. Dan
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Report this Post08-05-2013 03:07 PM Click Here to See the Profile for darkhorizonSend a Private Message to darkhorizonEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have seen more than a few GM v6's lose compression on one side of the motor before... Something to do with the valvetrain.
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TheRealShadowX
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Report this Post08-05-2013 04:03 PM Click Here to See the Profile for TheRealShadowXClick Here to Email TheRealShadowXSend a Private Message to TheRealShadowXEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by darkhorizon:

I have seen more than a few GM v6's lose compression on one side of the motor before... Something to do with the valvetrain.


I will run compression testing then.

Hopefully I don't need to dig into this engine. Worthless pile of 2.8
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Report this Post08-06-2013 02:25 AM Click Here to See the Profile for mitchjl22Click Here to Email mitchjl22Send a Private Message to mitchjl22Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by TheRealShadowX:


I will run compression testing then.

Hopefully I don't need to dig into this engine. Worthless pile of 2.8


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Report this Post08-06-2013 12:28 PM Click Here to See the Profile for FierobsessedClick Here to Email FierobsessedSend a Private Message to FierobsessedEdit/Delete MessageReply w/QuoteDirect Link to This Post
Your problem may be a bad injector driver in the ECM. Probably should just change the ECM.

You can test swap your green and blue wires and see if the banks swap with that, If it does swap with it. Your ECM has a fried injector driver. Otherwise it would have to be a wiring issue.

Remember, the ECM momentarily grounds the injector wires (green and blue) to fire them. The two INJ fuses just supply a constant source of 12V to the injectors.
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TheRealShadowX
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Report this Post08-06-2013 05:19 PM Click Here to See the Profile for TheRealShadowXClick Here to Email TheRealShadowXSend a Private Message to TheRealShadowXEdit/Delete MessageReply w/QuoteDirect Link to This Post
So, to do list.

Swap ECM.

If no change, do compression testing.

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TheRealShadowX
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Report this Post08-07-2013 12:46 PM Click Here to See the Profile for TheRealShadowXClick Here to Email TheRealShadowXSend a Private Message to TheRealShadowXEdit/Delete MessageReply w/QuoteDirect Link to This Post
Any last minute advice before I do testing?
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TheRealShadowX
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Report this Post08-09-2013 10:00 PM Click Here to See the Profile for TheRealShadowXClick Here to Email TheRealShadowXSend a Private Message to TheRealShadowXEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well, swapped ecm did nothing at all. If the compression test comes back fine, I assume that I have a bad wire between the injectors and the ecm. Seems about right, right?
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TheRealShadowX
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Report this Post08-09-2013 10:02 PM Click Here to See the Profile for TheRealShadowXClick Here to Email TheRealShadowXSend a Private Message to TheRealShadowXEdit/Delete MessageReply w/QuoteDirect Link to This Post

TheRealShadowX

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Do the injectors have their own dedicated grounds?
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rourke_87_T-Top
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Report this Post08-09-2013 11:24 PM Click Here to See the Profile for rourke_87_T-TopClick Here to Email rourke_87_T-TopSend a Private Message to rourke_87_T-TopEdit/Delete MessageReply w/QuoteDirect Link to This Post
unplugging the injector harness, check if the male / female pins are making connection, they oxidize so a drop of machine oil in the female ends, it's a simple troubleshoot.

[This message has been edited by rourke_87_T-Top (edited 08-09-2013).]

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Report this Post08-10-2013 12:00 AM Click Here to See the Profile for sleevePAPASend a Private Message to sleevePAPAEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by TheRealShadowX:

Do the injectors have their own dedicated grounds?


ECM supplies the ground, aka ground trigger.

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TheRealShadowX
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Report this Post08-10-2013 12:02 AM Click Here to See the Profile for TheRealShadowXClick Here to Email TheRealShadowXSend a Private Message to TheRealShadowXEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well, compression is between 95-110 for the 3 cylinders in question.

has to be a bad wire...
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phonedawgz
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Report this Post08-10-2013 01:22 AM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by TheRealShadowX:


Ok, so, Pink and Pink White, both have +12v, key on engine off.

Blue and Green have +12v, key on engine off.

Here's the kicker. Key on engine on BOTH still have +12v.... What gives?! Neither drops to 9v!

So... Neither bank should fire? Yet one is? Gaaaah...


You are measuring something wrong. If both stay at +12 then the injectors wouldn't be firing.

http://www.harborfreight.co...gic-probe-98709.html

You could use the $15.00 logic probe show here to see which flashes the probe from +12 to G. One light for each so it is more user friendly.

Start it and pull the inj1 fuse. See if that kills it. Then try the same with the inj 2 fuse.

Assuming only one of the fuses kills it, you at least have some proof positive of which side of the wiring harness it is. It is easy to connect the the injectors to either bank under the intake. Anyways once you have figured which fuse kills it, the trouble is on the other fuse. Pull the other fuse and determine which wire goes dead - the blue or the green. That will be the injectors that aren't firing. Pull the ECM connectors and with the key on stick a paper clip into that wire connector and short it to ground. Have someone listen to see if the injectors are clicking. They should when you short it to ground.

[This message has been edited by phonedawgz (edited 08-10-2013).]

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