06 4 weak cylinders after rebuild

chuggins10

chuggins10

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May 10, 2007
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I just finished up putting the new engine back in the truck last week and got everything finish and fired it up. 2-3 are firing correctly 1,4,5,6 are very weak. All 6 injectors are new BD remans. I can use the modis to shut down individually and you can only tell a difference when I shut of 2 or 3. I can pull the injector plug for 4-6 and not tell any difference in how it runs at all. I can pull the plug for 1-3 and it will stay running just very rough and rougher than just 2-3 only. Last night I could move the harness around and it would change tone now it wont do anything. I swapped 3 and 4 to see if maybe I got a bad set of injectors but still the same thing. Anybody have any ideas?? All the grounds are tight and on good contact. Unless there is one hiding I cant find.
 
Sometimes the injector harness can go bad, just a thought. Good luck!
 
The ecm on the 06 can compensate for a bad hole or two! That's one of the reasons people melt pistons! You just don't know there is a problem till it's to late! Bad fuel mileage is the biggest indicator of a problem!
 
If moving the harness around changed anything at all then I'd bet money it's bad, moving it around could have broken whatever connection that was already weak causing your problems. You can test it from the harness connection pins to the injector connections, but I would just go ahead and replace it.
 
Ohm the harness out and find the broken pin, crimp, or wire. Moving the harness around more than likely finished off whatever was going bad with it.
 
Harness tested good. Great continuity. Is there a way to test voltage to each injector while its firing to see if its getting the correct voltage?
 
Are you getting a lot of smoke. I know its stupid but are sure you adjusted your valves right. You had each cylinder on tdc when adjusted. If your valve is opening to soon could give you lower compression.
 
checked all the valves as well. it black smokes a little when I raise the rpm but not much. not even a white haze. I was thinking it would white smoke a little if I accidentally got the cam/crank a tooth or so out but would fire better than this
 
strokinnochokin said:
Harness tested good. Great continuity. Is there a way to test voltage to each injector while its firing to see if its getting the correct voltage?
Click to expand...

Use the lab scope on the modis. back probe the harness and use the graphing part
 
bump.
haven't figured it out yet. I replaced the injector harness then got a pin out to the plug and checked continuity and it tested fine. I swapped ecm's and it runs long enough for me to know its not the ecm. Im about to pull my hair out
 
strokinnochokin said:
bump.
haven't figured it out yet. I replaced the injector harness then got a pin out to the plug and checked continuity and it tested fine. I swapped ecm's and it runs long enough for me to know its not the ecm. Im about to pull my hair out
Click to expand...

Do a compression test, if its good see if someone has a known good set of injectors you can borrow.
 
good compression. I'm only getting 20-24 volts to the rear 3 and still getting 50 or so to the front. like I said I've been thru the whole harness, swapped ecm, swapped injectors around, ohm'd out the injectors, block to check grounds, everything else I can thing of. I've ran thru every test on shopkey and quickserve I can find and still no solution yet.
 
Chassis harness grounds? No electrical engineer but it could be one of the unswitched supplies or returns on the chassis side.

From my Not-So-Smart phone
 
biggy238 said:
Chassis harness grounds? No electrical engineer but it could be one of the unswitched supplies or returns on the chassis side.

From my Not-So-Smart phone
Click to expand...

I've check them over and over I'm going to go over all of the grounds again
 
partially broken wire in the engine harness?

or a wire in the engine harness pinched just enough to be a partial short?
 
You've exchanged everything from the ecm up. I don't have a schematic. I'm almost certain this is a resistive circuit on the truck side of the ecm harness.

Do you have the ability to build a bypass chassis harness?

From my Not-So-Smart phone
 
Figured it out!! HUGE THANKS to disturbed!! It ended up being the crank sensor although we're weren't getting any codes for the ckp and the modis showed it to be in sync with the cmp. Thank you to everybody that helped!!
 
So for learning how does that manifest the voltage you were seeing?

From my Not-So-Smart phone
 
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