Fuel injector knock

[Trgglynn]

Hey,
My engine has what appears to be a fuel injector knock. Balance rate on #5 is +1.25. Cylinder 5 compression is 380 (tested hot). Engine is low on power and downshifting a lot when driving. Seems irrelevant to temperature and the power level seems to fluctuate.

Can someone educate me to why an injector would knock?

when I say knock I mean it’s like a “tack tack tack” noise, independent of the overall injector ticking.

 

[2004LB7]

Codes should tell you what injector it is

Also, post up all the injector balance rates and main rate. Both while in park and another in drive

If the engine is in limp mode it will reduce power and you will have a different shift pattern

 

[Trgglynn]

Codes should tell you what injector it is

Also, post up all the injector balance rates and main rate. Both while in park and another in drive

If the engine is in limp mode it will reduce power and you will have a different shift pattern

Thank you for the reply. These were my most recent balance rates. I haven’t had any codes while driving, but I removed my fuel filter and drained the fuel, added 8oz of Diesel Power Service to the filter, reinstalled, primed with lift pump and bled air. When I started my RPM came up to about 450, hiccuped, went to normal idle, and popped P0193. Also, no limp mode. Just low power, excessive down shifting, and low fuel mileage.

 

[2004LB7]

Looks like you have a handful of leaking injectors. With the main rate that low there's a lot of extra fuel being injected and the ECM is trying to pull it back

 

[Trgglynn]

Looks like you have a handful of leaking injectors. With the main rate that low there's a lot of extra fuel being injected and the ECM is trying to pull it back

So I replaced the injectors with new Bosch injectors about two years ago. Ever since then it seems like the fuel rate has been low. This is based on getting them scanned at a shop a few months after install. Would high return rates make the fuel rate low? How about the FPRV or the FPR?

 

[2004LB7]

Fuel rate doesn't really effect the main rate until you get into the extremes. Ie: so low the injectors have a hard time providing the needed fuel or so high it's hard to control.

High return rates typically manifest in low fuel pressure which can cause hard starts and low power under higher loads.

The two main things that will cause a low main rate is the injectors putting in more fuel then the ECM is asking for. Or a badly written tune that has fuel tables that don't match the needs of the engine. So unless you have a bad tune or a set of oversized injectors without a matching tune for them then it's probably leaking injectors.

Where did you get your injectors from two years ago?

 

[Trgglynn]

Fuel rate doesn't really effect the main rate until you get into the extremes. Ie: so low the injectors have a hard time providing the needed fuel or so high it's hard to control.

High return rates typically manifest in low fuel pressure which can cause hard starts and low power under higher loads.

The two main things that will cause a low main rate is the injectors putting in more fuel then the ECM is asking for. Or a badly written tune that has fuel tables that don't match the needs of the engine. So unless you have a bad tune or a set of oversized injectors without a matching tune for them then it's probably leaking injectors.

Where did you get your injectors from two years ago?

Ah ok. So if I am understanding you right one possibility is that all the injectors are leaking/over fueling so the main rate is low? Something like not enough “restriction” from the injectors.

As far as I know the fuel pressure will reach 22-24kpsi. The truck starts up very easy.

I got my injectors from Lincoln Diesel. They’re Bosch new injectors installed 9/2021

2004.5-2005 OEM Genuine BOSCH® LLY Fuel Injectors **NO CORE CHARGE**

NO CORE CHARGE Required !!! Don't need your old Injector Cores? WE WILL PURCHASE YOUR CORES BACK FOR $450!!! See details below.

lincolndieselspecialties.com

I also replaced my CP3 in 11/2022.

LDS LBZ SuperStock CP3 Pump

Fit: 2001-2016 GM/Duramax LB7, LLY, LBZ, LMM, LML

lincolndieselspecialties.com

Also, truck is on stock tuning. YZ5 tuning

 

[Chevy1925]

You’re not the first one to have issues with Lincoln diesel injectors. Ever since they switched mfg, their stuff has gone down hill.

Basically the injectors are putting too much fuel in and the computer is pulling fuel back to keep idle rpm correct. Why it’s putting in too much fuel could be worn tips or pintle, bad sealing, nozzles are oversized/worn, poor rebuild and so on.

I’d suggest going with a set of s&s injectors or the like. Not cheap but also will not give you the issues you have.

 

[Trgglynn]

You’re not the first one to have issues with Lincoln diesel injectors. Ever since they switched mfg, their stuff has gone down hill.

Basically the injectors are putting too much fuel in and the computer is pulling fuel back to keep idle rpm correct. Why it’s putting in too much fuel could be worn tips or pintle, bad sealing, nozzles are oversized/worn, poor rebuild and so on.

I’d suggest going with a set of s&s injectors or the like. Not cheap but also will not give you the issues you have.

Well that’s unfortunate. However, these are supposed to be OEM new injectors.. is the issue with Bosch or what? At this point I cannot buy a new set or be down with my truck. They are under warranty so I can pull and send them in one at a time.

 

[Chevy1925]

Well that’s unfortunate. However, these are supposed to be OEM new injectors.. is the issue with Bosch or what? At this point I cannot buy a new set or be down with my truck. They are under warranty so I can pull and send them in one at a time.

The issue is with the lack luster rebuild shop most people use that at “Bosch certified”. I can go down the street and buy a set of reman Bosch injectors from a well known diesel supplier that services the US and they will pass on a bosch test stand but will cause smoke issues, knocking or won’t last. Send the same ones to exergy, s&s, flux or other good shops and they won’t pass.

See if they will warranty them. They have given everyone I know that has used their warranty, the run around at this point.

 

[Trgglynn]

The issue is with the lack luster rebuild shop most people use that at “Bosch certified”. I can go down the street and buy a set of reman Bosch injectors from a well known diesel supplier that services the US and they will pass on a bosch test stand but will cause smoke issues, knocking or won’t last. Send the same ones to exergy, s&s, flux or other good shops and they won’t pass.

See if they will warranty them. They have given everyone I know that has used their warranty, the run around at this point.

For sure, very similar story for the Ford 7.3L injectors as well.

Here’s my question though, my units were advertised as new, not reman. So what would make them knock so badly? Are Bosch injectors actually that fragile?

 

[2004LB7]

At this point I wouldn't trust that the injectors from LDS are 100% from Bosch and not touched by someone else or as James said, more then likely a Bosch "certified" shop that is rebuilding them. But with sub standard quality control so many will make it out that shouldn't

Are LDS injectors still only 12 months warranty?

 

[Trgglynn]

At this point I wouldn't trust that the injectors from LDS are 100% from Bosch and not touched by someone else or as James said, more then likely a Bosch "certified" shop that is rebuilding them. But with sub standard quality control so many will make it out that shouldn't

Are LDS injectors still only 12 months warranty?

Food for thought, when I got mine they came individually packaged in a Bosch package and sealed in Bosch branded plastic, with all the dust cover inserts of course. The new units have a 3 year warranty on them, which IIRC I warrantied one of them last year. Couldn’t tell you which hole it came out of but I bought another new injector, sent the old one back and they refunded me for the injector I purchased. Personally I haven’t had any issues with them but I can’t afford to go that route, at least as of right now.

What is weird is on my drive home just a few minutes ago, probably 10-15 miles, my truck seemed to snap out of “feeling heavy” and had good acceleration and my mileage went up to 19-21 cruising. It didn’t last long, but whatever is going on is intermittent and varies with severity.

 

[Chevy1925]

Really doesn’t mean much. So do the injectors I talked about earlier.

Take advantage of the warranty. Most likely a solenoid going out

 

[kidturbo]

A little dielectric grease on the connectors goes a long ways sometimes. I always say start with the electrical side, as a simple latch not snapped in all the ways has got me before. So simple to just disconnect each one and put a bit of grease on em, and reconnect. The slightest voltage related problem can have you chasing the wrong thing. Second, monitor the fuel pressure commanded vs actual and be sure it tracks pretty much spot on. While you have one injector balance slightly elevated, it doesn't always equate to an injector being the issue.

 

[Trgglynn]

Really doesn’t mean much. So do the injectors I talked about earlier.

Take advantage of the warranty. Most likely a solenoid going out

For sure. I don’t have any codes coming up. Any way to test the injector(s) before pulling them and mailing them? I’ve considered doing a “bottle test”, but need to research more about it. As far as I understand a bottle test wouldn’t necessarily pinpoint any one injector.

 

[Trgglynn]

A little dielectric grease on the connectors goes a long ways sometimes. I always say start with the electrical side, as a simple latch not snapped in all the ways has got me before. So simple to just disconnect each one and put a bit of grease on em, and reconnect. The slightest voltage related problem can have you chasing the wrong thing. Second, monitor the fuel pressure commanded vs actual and be sure it tracks pretty much spot on. While you have one injector balance slightly elevated, it doesn't always equate to an injector being the issue.

I’ll give the grease a go! I need to get a hold of a capable tuner. I ordered a Bullydog GT a couple years ago. I stopped using the times a good while ago but it’s what I use to monitor rail and boost. It seems consistent between now and before I was having issues.

 

[Trgglynn]

Really doesn’t mean much. So do the injectors I talked about earlier.

Take advantage of the warranty. Most likely a solenoid going out

Any advice on how to narrow down which one is faulty? I don’t have any codes.

 

[Bdsankey]

Another one here for issues with LDS as well as "Bosch Certified" rebuild houses. I know of only a few companies I can call and guarantee I'm getting a genuine Bosch product. I've had multiple local customers (I'm local to LDS) have issues on initial startup or fail very very shortly after being installed. We won't touch anything LDS based.

I've had the same experience as James where a customer brought in Bosch sealed boxes/bags and the injectors were smoky/hazy piles of garbage. Sent them to a reputable injector house and they failed (this set went to Exergy when it occurred).

Any advice on how to narrow down which one is faulty? I don’t have any codes.

In my opinion no, with balance rates as low and a main rate that low as they are I would bet it's not just one injector having issues. Your best bet would be to call LDS and explain the condition you have, your concern, and the diagnostic work you've done thus far.

They likely will give you the runaround.

 

[Trgglynn]

Another one here for issues with LDS as well as "Bosch Certified" rebuild houses. I know of only a few companies I can call and guarantee I'm getting a genuine Bosch product. I've had multiple local customers (I'm local to LDS) have issues on initial startup or fail very very shortly after being installed. We won't touch anything LDS based.

I've had the same experience as James where a customer brought in Bosch sealed boxes/bags and the injectors were smoky/hazy piles of garbage. Sent them to a reputable injector house and they failed (this set went to Exergy when it occurred).


In my opinion no, with balance rates as low and a main rate that low as they are I would bet it's not just one injector having issues. Your best bet would be to call LDS and explain the condition you have, your concern, and the diagnostic work you've done thus far.

They likely will give you the runaround.

Well in that case, do you know of a reputable place to order fuel injectors?