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 2008 C7 #6 Injector issue
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Hicrawler
New Member

9 Posts

Posted - 10/16/2012 :  09:40:02 AM  Show Profile  Visit Hicrawler's Homepage  Reply with Quote
I'm trying to diagnose why number 6 injector keeps failing the cylinder cut out test. When first tested number 4 and number 6 injector failed the test. I replaced both. Entered the new fuel trims. Got the bus to 170 and ran another test. Number 4 passed and number 1 and 6 were questionable. I replaced number 1 and 6 for the second time as well as the injector harness. I have rounded the plug at the front of the block on the fuel rail so I can't inspect for metal there. I have removed the top cover on the HEUI pump and have no metal flake in the top of the pump. Any suggestions as to why Number 6 keeps failing a Cylinder Cutout test using Cat Electronic Technician?

Hicrawler
New Member

9 Posts

Posted - 10/16/2012 :  10:00:06 AM  Show Profile  Visit Hicrawler's Homepage  Reply with Quote
The last service was performed on 10/3/12. All filters and oil have been changed as well at this service. Our fleet changes oil and filters on the C7 motors every 6,000 miles.
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Tb4020
Senior Member

United States
65 Posts

Posted - 10/17/2012 :  03:35:55 AM  Show Profile  Reply with Quote
There are very small holes in the rocker rail that spray oil on the injector solenoids to keep them cool if those plug it will cause injector issues. The smallest torch tip cleaner will just fit in the hole. That engine should still be under warranty? 07 emissions?
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Hicrawler
New Member

9 Posts

Posted - 10/17/2012 :  06:32:52 AM  Show Profile  Visit Hicrawler's Homepage  Reply with Quote
The warranty ran out last year on this bus. We bid for a 5 year warranty on all of our motors that starts from the day we receive the bus. Not the actual in service day. I have tested further than the injector by removing the push rods on both intake and exhaust valves, and adding pressurized shop air to the cylinder through the injector hole with the injector removed. Theoretically by removing the push rods the valves should be completely closed and if the rings are sealing properly I should not hear any air escaping from the cylinder. After performing this test I can hear air escaping from somewhere. I have not been able to pinpoint where the air is going yet. Looks like I will be removing the head for further inspection.
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Hicrawler
New Member

9 Posts

Posted - 10/17/2012 :  07:24:28 AM  Show Profile  Visit Hicrawler's Homepage  Reply with Quote
Tb4020: I have verified that the oil gallies are clear of debris and are injecting oil properly.
Thank you for the response.
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Tb4020
Senior Member

United States
65 Posts

Posted - 10/17/2012 :  07:55:21 AM  Show Profile  Reply with Quote
Is this an 07 emissions motor or a pre 07? I wouldn't pull the head yet, when you have a pan off and roll a motor you will hear air going past the rings. There is a spec for crankcase pressure, if a pre motor I would change the fuel pressure regulator at the back of the Head first. There might not be enough fuel pressure at number 6 to fire properly.
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Offroadwolf
Active Member

41 Posts

Posted - 10/18/2012 :  3:28:23 PM  Show Profile  Visit Offroadwolf's Homepage  Reply with Quote
Since youve rounded the head on the front oil galley plug, use an air hammer with a chisel bit on the edge of it and turn the plug, Ive done it a hundred times. Then run a clean long magnet all the way to the back of the galley and see if you pull out any metal, thats where it will sit. Also pull the fuel pressure regulator off the engine and take it apart. Unscrew the two halves and then an allen to take the center screw out, if its bad that where the blown o-ring will be.
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Hicrawler
New Member

9 Posts

Posted - 10/19/2012 :  03:43:21 AM  Show Profile  Visit Hicrawler's Homepage  Reply with Quote
A big thanks to both of you Tb4020 and Offroadwork!!! Even though I did not see both of your postings until after I had removed the head. I did remove the front plug which was rounded using Offroadwolf's technique. I will use this technique again because it works very well. I also removed the fuel pressure regulator and the o-ring has split. I will replace the fuel pressure regulator and re install the head. I'll keep you updated with the progress but I'm confident that this will fix the issue.

Thanks again for the great information. Now that I have found this forum and it has helped me I will continue to look through the new postings and try to offer helpful information to someone else.
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bwest
Administrator

United States
2268 Posts

Posted - 10/19/2012 :  6:50:22 PM  Show Profile  Reply with Quote
quote:
Originally posted by Hicrawler

A big thanks to both of you Tb4020 and Offroadwork!!! Even though I did not see both of your postings until after I had removed the head. I did remove the front plug which was rounded using Offroadwolf's technique. I will use this technique again because it works very well. I also removed the fuel pressure regulator and the o-ring has split. I will replace the fuel pressure regulator and re install the head. I'll keep you updated with the progress but I'm confident that this will fix the issue.

Thanks again for the great information. Now that I have found this forum and it has helped me I will continue to look through the new postings and try to offer helpful information to someone else.



Awesome! That's the way it works.

Bryan
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Wolf0r
Top Member

USA
2177 Posts

Posted - 10/23/2012 :  06:45:40 AM  Show Profile  Reply with Quote
Was the injector over or under fueling? I'm trying to understand this, I never worked on a 07 CAT that deep. Common rail system right?

“The good thing about science is that it's true whether or not you believe in it.”
Neil deGrasse Tyson
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Offroadwolf
Active Member

41 Posts

Posted - 10/23/2012 :  07:51:08 AM  Show Profile  Visit Offroadwolf's Homepage  Reply with Quote
Might be a little late but you need to look in the high pressure oil rail for any signs on metal in there. Any metal in that area is coming from the HEUI pump. And the only fix at that point is a new pump and 6 new injectors, and make sure you flush the high pressure rail in the head really good, and change the oil and filter also. The C7's have had this problem for years. CAT won't tell anybody what they have changed in the pumps to eliminate this problem. All the ones I replaced under warranty didnt comeback a second time. So I can only assume they know what the problem was and have made a change in the pump to cure it.
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Hicrawler
New Member

9 Posts

Posted - 10/25/2012 :  03:23:01 AM  Show Profile  Visit Hicrawler's Homepage  Reply with Quote
Wolf0r: The injector was under fueling. The motor had a misfire in #6. I found a split o-ring when I removed the fuel pressure regulator which was not allowing the regulator to close. I have not had time to get the head back on because of other work going on in the shop currently. But when I removed the allan plug in the front of the head and ran a magnet to the back of the head there were no metal debris. This is a common rail system.

Offroadwolf: The oil and filters were changed 7 miles ago when the service was performed and I tested the injectors. No metal has been found in the oil. I have removed the top cover on the heui pump to check for metal debris, and no metal was found. This was done after the oil was changed though.
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