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Discussion Starter #1
Hey guys, this is my first time on here so if this is in the wrong area I apologize.

Long story short I replaced all 6 injectors and the crossover tubes. I followed all the torque sequences to the T except for the fuel lines from the rail ( I can't get my torque wrench onto them ).

I fired my truck up and it did its typical idle after new injectors and then cleaned up. I drove the truck and notice the rail pressure won't build and it started sputtering like it would die. Once home it idled the same way.

This morning I fired it up and it idled fine at first but then started sputtering/surging again.

I see no visible fuel leaks and I have no idea where to even begin diagnosing this. Any help would be very appreciated.
 

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What year is your truck? Why did you replace the injectors to start with? What injectors did you buy for the replacements?
 

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What year is your truck? Why did you replace the injectors to start with? What injectors did you buy for the replacements?
I have an 03. I replaced them due to white smoke/rough idle and hard starts. They were tested and failed. I replaced them with 50% injectors which were the size i had in there originally. Premco is the company I bought them from
 

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I have an 03. I replaced them due to white smoke/rough idle and hard starts. They were tested and failed. I replaced them with 50% injectors which were the size i had in there originally. Premco is the company I bought them from
Hate to tell you this but there are reputable dealers for injectors and not so reputable. I would guess you got some cheap bad injectors. Reason everyone here says to get new bosch injectors or BBI injectors.
 

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With their reman injectors? Quick search of the forum shows people have had many issues with them.

No surprise when 9.9/10 remans are junk.
 

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Hate to tell you this but there are reputable dealers for injectors and not so reputable. I would guess you got some cheap bad injectors. Reason everyone here says to get new bosch injectors or BBI injectors.
What baffles me is the truck fires up and runs great then slowly I start noticing rail pressure flucations and then soon after I can hear it in the exhaust. What is my best plan of action to diagnose this ? I have a lot of friends who run premco and love them. Only 1 person I know talks bad about them and his motor had severe issues before he even installed them.
 

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What baffles me is the truck fires up and runs great then slowly I start noticing rail pressure flucations and then soon after I can hear it in the exhaust. What is my best plan of action to diagnose this ? I have a lot of friends who run premco and love them. Only 1 person I know talks bad about them and his motor had severe issues before he even installed them.
Sounds like something is failing or going out of spec when hot. Not an uncommon event. If the motor is healthy and has no blow by honestly I would get a set a known good injectors. Many threads here to point you in the right direction.
 

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Have you replaced the FCA? Those can get stuck.
 

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Yes I replaced the fca and checked the cp3 unplugged to see if it was building rail pressure
Do you have good lift pump pressure to the CP3?
 

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Quit throwing parts at it and test for the real cause. These HPCRs will bankrupt most owners with just parts throwing and all they end up with is a melted down Cummins with hole in block.

Even Bosch can't rebuild their own HPCR injectors so they are reliable, well balanced and don't melt motors down into holed blocks. Some say they have good luck so far with the BBI rebuilds.
For me new BBIs or new Factory Bosch only. There is no such thing as good rebuilt HPCR injectors except maybe the BBIs. The owners are retired Bosch engineers
Consider your "rebuilds" as learning lesson only, pull out before you burn down/melt pistons and send a rod through the block

Start with measuring the individual and all 6 injector return fuel leakage amounts. Need at least 1 injector block off tool.

if it has the OEM factory line POS lift pump motor mounted, toss that now. Put on a real fuel pump, Walbro or Holley electric along with Wix fuel filter screw on bases and HD commercial large 3 micron dirt filter plus separator HD water separator. Don't need an overpriced boy toy fuel pump.

Get an accurate digital fuel pressure gauge on it, Edge Insights, will monitor and display just about everything from data port. Add a low pressure fuel pressure sensor for output psi from lift pump at the input to CP3. These Dodge pickup diesel tank fuel pickups plug too often from all the water, dirt and slop from pipeline/tanker/retail station garbage fuel.
 

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Discussion Starter #14
Quit throwing parts at it and test for the real cause. These HPCRs will bankrupt most owners with just parts throwing and all they end up with is a melted down Cummins with hole in block.

Even Bosch can't rebuild their own HPCR injectors so they are reliable, well balanced and don't melt motors down into holed blocks. Some say they have good luck so far with the BBI rebuilds.
For me new BBIs or new Factory Bosch only. There is no such thing as good rebuilt HPCR injectors except maybe the BBIs. The owners are retired Bosch engineers
Consider your "rebuilds" as learning lesson only, pull out before you burn down/melt pistons and send a rod through the block

Start with measuring the individual and all 6 injector return fuel leakage amounts. Need at least 1 injector block off tool.

if it has the OEM factory line POS lift pump motor mounted, toss that now. Put on a real fuel pump, Walbro or Holley electric along with Wix fuel filter screw on bases and HD commercial large 3 micron dirt filter plus separator HD water separator. Don't need an overpriced boy toy fuel pump.

Get an accurate digital fuel pressure gauge on it, Edge Insights, will monitor and display just about everything from data port. Add a low pressure fuel pressure sensor for output psi from lift pump at the input to CP3. These Dodge pickup diesel tank fuel pickups plug too often from all the water, dirt and slop from pipeline/tanker/retail station garbage fuel.
I apologize for the late reply.

The injectors were done because 5/6 failed testing at a trusted shop. I had symptoms of bad injectors too so I definitely needed to have them fixed. Tomorrow ill be done reinstalling them to see if maybe there was a fuel leak. I noticed the issue got progressively worse and I noticed moisture towards the 5th and 6th lines.

I have always had a fass on this truck so I thankfully dont need to worry too much about that portion.

As far as my cp3, I did the test where you unplug it to see if it maxes rail pressure and it does. I also put a new fca. The pump itself is an upgraded one to flow more
 

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Discussion Starter #15
Quit throwing parts at it and test for the real cause. These HPCRs will bankrupt most owners with just parts throwing and all they end up with is a melted down Cummins with hole in block.

Even Bosch can't rebuild their own HPCR injectors so they are reliable, well balanced and don't melt motors down into holed blocks. Some say they have good luck so far with the BBI rebuilds.
For me new BBIs or new Factory Bosch only. There is no such thing as good rebuilt HPCR injectors except maybe the BBIs. The owners are retired Bosch engineers
Consider your "rebuilds" as learning lesson only, pull out before you burn down/melt pistons and send a rod through the block

Start with measuring the individual and all 6 injector return fuel leakage amounts. Need at least 1 injector block off tool.

if it has the OEM factory line POS lift pump motor mounted, toss that now. Put on a real fuel pump, Walbro or Holley electric along with Wix fuel filter screw on bases and HD commercial large 3 micron dirt filter plus separator HD water separator. Don't need an overpriced boy toy fuel pump.

Get an accurate digital fuel pressure gauge on it, Edge Insights, will monitor and display just about everything from data port. Add a low pressure fuel pressure sensor for output psi from lift pump at the input to CP3. These Dodge pickup diesel tank fuel pickups plug too often from all the water, dirt and slop from pipeline/tanker/retail station garbage fuel.
And also they will be sent back to get a full check under warranty if I still have issues.

What confused me was this:

The truck fired up rough at first like most do after injector installs and then cleared up and idled amazing. 45 seconds or so after putting it into drive I noticed rail pressure dropping and then bouncing back up when I let off the gas. I parked it and the following day fired it up to see what I could find and it would barely even idle.

What issue could cause the truck to run good initially but very quickly deteriorate its performance? My thought was maybe a fuel leak that got worse as the truck vibrated.
 

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And also they will be sent back to get a full check under warranty if I still have issues.

What confused me was this:

The truck fired up rough at first like most do after injector installs and then cleared up and idled amazing. 45 seconds or so after putting it into drive I noticed rail pressure dropping and then bouncing back up when I let off the gas. I parked it and the following day fired it up to see what I could find and it would barely even idle.

What issue could cause the truck to run good initially but very quickly deteriorate its performance? My thought was maybe a fuel leak that got worse as the truck vibrated.
A lot of things. Might have to send a couple things away. You said yours was 03? Check to see if power is leaking from the injector harness to ground or any shorts. My biggest concern would be a pintle in an injector hanging when it warms up- should be white smoke on that. Might be an injector driver in the ECM that’s getting weak- but that and the injector harness shouldn’t create low rail pressure where as an injector problem will. Rail relief will as well. Any chance you ended up missing a injector washer when you did those? Sometimes they get stacked and it does sound like a possible internal fuel leak. Next on the list could be your lift pump. The frame and fuel housing mounted ones haven’t been as reliable as the in tank ones.


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Did you ever check your rail pressure relief valve?
 
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