I just put in my mach 6's and after tightening everything up and getting it started it runs very rough. Sounds like it may only be firing 4 or 5 of the cylinders, even under load it still seems the same ...very rough with a miss. Could this be air in the lines? Maybe one of the lines isnt tight enough? Could air still be trapped in there? I am going to try and retighten everything to see if this helps? any other suggestions?- o-rings seemed to be in very good shape. Nothing else seems to be wrong. Fired up initailly almost right away just has a terrible miss???
thanks in advance
-alex

 

did you make sure that there are no doubled up washers? that will throw the timing and spray in the piston bowl off. not sure if it will make it run that rough.

 

Mine ran rough and skipped after I put in my injectors but just had air in there still. I ran it about 1700rpm for a short while and it bleed out and runs fine . Good luck!

 

im sure there are no double washers and ive tried running it, rebleeding it, holding it at high rpms and it still runs like it is down a cylinder? I don't know what else to try short of taking the injectors back out, cleaning them, putting on new o-rings and washers and reinstalling them. I really don't want to do this because I don't have the time, any other suggestions?
Thanks again,
Alex

 

i take you have checked and rechecked the back 2 injector lines for leaks? a small leak will cause a terrible idle

also is it possible that you could have mixed up a mach 6 and one of the older injectors? different pop offs might cause it to run rough

 

IF the nuts are tight you have work to do--it's most likely one of the issues above, but it could be you have a bad injector or two--it will suck if you tear it apart and can't diagnose the problem---then what injectors to put back in??? good luck...........chris

 

Alex, I know you didn't mix up the old ones because I have your old ones. Check all your connections, make sure you have no leaks. Some trucks just seem to take longer to bleed the air out of the system then others, after an injector change.

I helped a buddy swap injectors about a month back, when we pulled his old DD1s out we had 6 injectors and 8 washers, two injectors had double washers on them and the truck ran great.

 

Yea, it couldn't be that I have the wrong injectors in their. And i have the six old washers sitting on my bench so it can't be that either! As for the lines I have them TIGHT!!! If it was just a rough idle it wouldnt worry me, but im almost positive im down a cylinder ...truck dosnt accellerate right?? anyone have any ideas, i don't think this problem will work itself out just by running it.

 

Air in the system would make the truck run rough at any rpm, and cause a miss like you are describing. Have you driven the truck at all? If it doesn't bleed out, and the rough running persists, then you may have a bad injector.

Did the Mach 6s have washers on them when you got them? If so did you replace them with new ones? The reason I ask is I had to look very closely at the DD1s I pulled out to notice the extra washer. It wasn't glaringly obvious, but after I found the one I looked at the others again and noticed another one with an extra washer. I know with the DD1s it didn't make much difference, if any at all, but they are only a 50hp injector, with something as big as a Mach 6 it may well make a big difference.

 

orings, overflow valve???? did you tighten all the injector hold down bolts???---it ran fine before and you have no leaks and fuel pressure is good---so unless you're having a box issue it has to be an injector issue---chris

 

I had to install my M4s twice due to operator error. Mine were leaking compression pressure into the fuel return and giving me a pressurized fuel tank. Not good to open the fuel filler and see hot vapor pouring out.

You have to have them seated firmly, but gently into the heads. You also have to be careful in how you tighten the 8mm injector hold down screws and the 19mm injector line nuts. Alternate them, and go sloooooow. If there's any misalignment in the crossover tube, you'll have problems.

DO NOT OVERTIGHTEN THE 19MM NUTS! Tighten them just enough to where there's no leakage. This is the reason my truck didn't run right.

I removed my new M4s, examined each one closely (along with the engine to see if there were extra washers down in there) and carefully RE-installed each one.

It fired right up, cleared the air out of the lines and purred like a kitten.


BEST INJECTOR INSTALL TIP: Use a short stubby 19mm wrench to tighten the line nuts. You have to be he-man to overtorque them with such a short little wrench. It also makes it a lot easier to maneuver when doing the back two cylinders.

To loosen those nuts, feel free to use as long a wrench as you can get back there. i used a longer 3/4, which is close enough to 19mm to work without mucking up the nuts.

Second best injector install tip: When you first insert the new injector, leave the bolt screwed into the top and whack it good a couple times with a non-steel hammer or mallet (rubber or hard plastic). This will certainly seat them where they're supposed to be. Obviously the back cylinders will need a different approach. On the back, I pried down with some REALLY long needlenose pliers on seated them that way.

Learn from my mistakes!

Justin

 

Maybe I overtightened the 19mm lines...I do have them VERY tight...I didnt know you could make them TOO tight. I will try this tommorrow. Also when installing the back 19mm nut it was difficult to thread in, after several tries i got it but it didnt spin very freely, could something be misaligned?

 

they need to be fairly tight or they can come loose over time and start leaking---chris

 

I really appreciate all the fast responses, this was my first time and I had no directions so It dosnt suprise me. I guess I was alittle TOO adventurous. If anybody has any other suggestions that would be great, Im trying to get a list of things to check tommorrow.
Thanks again,
Alex

 

So what was the Fix for this? I am having the same problem right now! LMK

Thanks,
Josh