lml won't start/ long crank to retire after it gets warmed up [Archive] - Duramax Diesels Forum


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09-01-2016, 08:08 AM
i replaced the cp4 pump only and cleaned entire fuel system last week. Finally got the truck to fire and run. it takes 20-30 pumps to get the primer firm. it has no visible leaks around it and all the lines from it. when the motor is cool it fires right up. after running for 5-10 minutes and shut it off, it will no start. i have no codes either. Any help would be much appreciated

09-01-2016, 08:09 AM

09-01-2016, 08:28 AM
is there a sure fire way to check injectors? i was told balance rates should be =/-.2 which all mine stay in that range. #1 -1.24, #2 0.56, #3 0.44, #4 -2.45, #5 0.45, #6 3.81, #7 -3.15, #8 0.67

09-01-2016, 09:59 AM
okay i did a little more digging and started to do a bottle test, fuel is pouring out of the return. i also noticed the supply line has 2 kinks in the little 5 inch section of braided hose

09-01-2016, 10:09 AM
Yea I had an 11 that blew the cp4. Replaced the cp4, cleaned everything and it started ok for a little bit. Once it was running it ran fine. It quickly got worse and worse until it wouldn't start without starting fluid. Did the bottle test and checked the returns and they were returning just too much fuel to build enough pressure to start. balance rates won't tell you the full story. I would put money on it that you will have to replace all the injectors and maybe fpr. $1900 for new bosch injectors otherwise I would call Hicksville Auto Recyclers for used ones, they dont really go bad unless you run a bunch of crap through them. Piezo injectors have an extremely low tolerance for debris.

09-01-2016, 10:19 AM
The FPR has that metal screen on it so i would take that out and make sure it doesn't have any shavings plugging it up.

09-01-2016, 11:22 AM
The for on the rail? Cause the one on the pump is brand new

09-01-2016, 11:27 AM
Yes the one on the drivers side rail.

09-01-2016, 04:49 PM
You drop and clean your tank?

09-01-2016, 05:50 PM
yes tank was dropped and clean. drove the truck for 2.5 hrs today and it ran flawless, just couldn't shut it off because it will not start back up until it has cooled off. i ran the match tools maximus 2.0 scan tool for the entire ride and the injectors as well as the fuel pressure were perfect the entire time. i just pick up a new fprv to replace old one since I'm returning half a coke bottle just on start up and 10 second idle. should have it swapped out within a few hours. i also ordered a new fuel supply line since mine has 2 kinks in the braided portion where it connect on the side of motor

09-01-2016, 11:15 PM
new fprv is in. it did not totally fix the problem. it is not returning as much fuel as before but still to much none the less... all injectors maybe? i guess i will be pulling the returns off the injectors one by one tomorrow to see which is returning to much fuel...

09-02-2016, 08:10 AM
Yep I think you are going to need to do injectors my friend. At least they are not that bad to do. If you have a hoist it makes it much easier. Pull the inner fenders and you can do the whole job from underneath. I drove my truck all the way back from Mississippi to Michigan and didn't shut it down the whole time because I knew it wouldn't start again.

09-02-2016, 09:57 AM
do i need that special tool to remove the injectors?

09-02-2016, 11:30 AM
someone told me to take the return lines off of the injectors and check to see how much fuel they are returning. they also said it should only be a squirt out of each injector. my injectors are only returning a couple of drops, but fuel is still pouring out of the the return lines them selves. is there a regulator in the return line system or something else that could be giving me me that excess fuel

09-06-2016, 06:21 AM
You shouldn't need special tool, I just put a pry bar under the fork that holds them in a they popped right out. GM has a special way of testing them. There is only a certain amount of ml they can be allowed to return per how many cranks. Have you bottle tested all of the injectors yet?