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#1 · Nov 4, 2009 Do we have any Cat mechanics or parts people on the board here? Looking to get some C7 and 3126 information. Please send me a pm if you could help Thanks Kevin Sort by Oldest first Oldest first Newest first Most reactions #2 · Nov 4, 2009 c7's have a lot of injector and heui pump problems. i have personal had 6 trucks at work i have had to replace 2 to 3 injectors in. also have had a couple i have done all 6 injectors in. we have had 2 trucks that have had heui (hydraulic electronic unit injector) pumps go bad. i have not been really happy with them. also dont have a lot of power. our cummis ism's are a much better motor hardly ever have problems with them also seem to have more power. well that is my 2 cents someone might have a different opinion. #6 · Apr 2, 2011

BrandonWatts said: c7's have a lot of injector and heui pump problems. i have personal had 6 trucks at work i have had to replace 2 to 3 injectors in. also have had a couple i have done all 6 injectors in. we have had 2 trucks that have had heui (hydraulic electronic unit injector) pumps go bad. i have not been really happy with them. also dont have a lot of power. our cummis ism's are a much better motor hardly ever have problems with them also seem to have more power. well that is my 2 cents someone might have a different opinion.[/QUOT I have a C-7 in a C6500 GMC and seem to have a problem w/ either injector,s or HEUI pupm, as told by pulling codes from engine. How can I narrow down which of the 2 above mentioned is the problem? Thx very much for Ur input Click to expand...

1 Reply #3 · Nov 6, 2009 For the most part they are the same engine. I think they are both JUNK!!! I agree with Brandon the HEUI injection system is crap. It is basicaly the same system that the powerstrokes use. #4 · Nov 7, 2009 Unless the engine is hot (stolen)(and even then), why not ask away here??? What happened??? Running poor? Hard Starting? Oil Cooler Leaking? Front Seal Leaking? Looses Prime? Wanna uprate? Rocker Boxes Leaking? Can't think of any other common points of problems. #5 · Nov 7, 2009 have to agree with all of the above the 3126 doesnt seem to have as many problems. we have a loader with that engine an older one and it is a good engine. the c7's are just junk plan and simple maybe that is why cat isnt building over the road engines anymore after 2009. they are teaming up with navistar. the maxx 15 will be a cat bottom end which have always been strong with a navistar upper end, turbo, head, egr system. 0 Reply #7 · Apr 10, 2011 We hace a couple of fl70's at work with 3126's they are god awful gutless but remarkably reliable only water pump replacements #9 · May 14, 2011 is a C9 any better ? #10 · May 15, 2011 For the most part they are, heui problems are not as common but do happen. Biggest problem on the C9's I've seen is fuel in oil which is injectors or seals leaking and oil pressure problems which are mostly caused by the bypass valves in the pump. Went out on 2 C9's last week, one was an overheat problem in an 800 hour C9 the other was a low oil pressure problem. Got a job monday on a C9 for high oil pressure, depends alot on what application the engine is in and how well the its maintained. 0 Reply #11 · May 26, 2015 C7 CODES Need help on a 2008 GMC c6500 c7 cat engine. I have a lot of erratic codes. 157-17 157-15 and low coolant code always coming on with good level in the tank #12 · May 26, 2015 c7 157-15 and 157-17 codes I have a 2008 gmc c6500 with a c7 cat engine. engine light comes on after driving, it trips 157-15 and 157-17 fuel codes and low engine coolant code all the time. change fuel pressure sensor and pressure relief valve. got better and has a little more power but engine light still comes on runs a little rough. any ideas? thanks Isuzu #13 · Aug 21, 2016 c7 eng miss I have a CAT C7 that is showing fault codes 2-11, 3-11 and 4-11 active. All injectors are new and #2 & #4 have been replaced 3 times, installed new injector harness under valve cover. Installed test ECM from a running truck that had no fault codes - all 3 injector faults became active using test ECM. Removed eng harness from rocker cover connection down to the ECM, tested and loaded harness using a 12 volt head light -harness showed good but to my understanding the ECM send up to 100 volts through harness? Cut old injector harness up and made a jumper connection that ran from #5 inj connector to #2 inj. Performed injector solenoid test - still showing #5 injector ( actually #2 injector faulty "shorted" due to using jumper harness. I can unplug #4 injector solenoid and #3 inject fault goes away and solenoid test passes??? Can anyone please help!!! Truck is a 2005 Freightliner M2. This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread. Insert Quotes Post Reply

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