Lbz Fuel Knock

Shawn T · October 20, 2009

Recently, I am getting a really loud knock out of my LBZ. Only 41000 miles and it only does it when it's cold. It sounds like a no-fuel in at least one cylinder. As soon as it warms up, it goes away. Not normal. Started about 3000 miles ago. Only prob, I've seen with the LBZ motor is a sticky EGR valve. I can pretty much rule this out, as it does not blow an ounce of smoke. Help is appreciated. Semi-plugged injector maybe? I need a diesel mechanics opinion. I posted this on the HD topic and not really getting a sure response. Do I take it in, or try some addative, and which brand? Please help.

gmtech4 · October 20, 2009

Im pretty sure you have warranty ,take it in,they will run your vin and see ,,do not leave this condition to long ,over fuel means not a good ending for the pistons,

I saw a truck in northern BC that drove in with a bit of a miss ( more like a thump thump thump),after the head was removed ,there was no piston ,just a connecting rod making a rather large groove in the cyl wall,it was crazy

do not delay

Shawn T · October 21, 2009

Im pretty sure you have warranty ,take it in,they will run your vin and see ,,do not leave this condition to long ,over fuel means not a good ending for the pistons,

I saw a truck in northern BC that drove in with a bit of a miss ( more like a thump thump thump),after the head was removed ,there was no piston ,just a connecting rod making a rather large groove in the cyl wall,it was crazy

do not delay

Ok, well I made an appointment for Monday and the service writer really had no clue what I was talking about, hopefully she is just a pencil pusher and has a good mechanic drive it and take a look. This better not be a "cannot duplicate" issue. That seems to be famous when it comes to Duramax issues. Thanks for the help.

gmtech4 · October 22, 2009

the writer does just that ,writes the complaint and upsells crap,,for you not to get a "could not duplicate " you have to leave it overnight,and then they can duplicate it ,give lots of info ,speeds ,etc,

do not tell them what you think,they don't care,tell them the noise only etc.

good luck ,let us know

the scanner never lies lol

Nytemare · October 22, 2009

do not tell them what you think,they don't care,tell them the noise only etc.

the scanner never lies lol

True that...LOL

Shawn T · October 27, 2009

Update: No codes, no low injector pressures. Everything checks out from top to bottom. The mechanic seemed knowledgable and honest. We took it for spin cold, and it knocked. After it hit about 100 degrees it started to quiet and then at 180 it quit all together. He definately heard the knock and acknowledged it's there. The fact of the matter is, it's just injector knock caused by a couple of things

1. Ultra Low Sulfur diesel is very dry and has 0 lubricating properties.

2. When LBZ's get watered-down fuel, it usually only takes once to make an injector noisy

He stated that with his experience that the LBZ's seem to be the most tempermental about water induced fuel and the Ultra Low Sulfer diesel is hell on these motors. He told me there is a line of the old 6.5 diesels with problems stemming from it.

I left it with him, he is going to add some additive and run it through. I think it's called Benzanine? Anyway, he said theres a 50/50 chance it will quiet it down. If it does not, he said he will gladly chase down the chattery injector but it's not a guarantee it will ever quiet down.

Have you seen this a lot lately too?

Nytemare · October 27, 2009

Well its good that someone did hear it. Something to go back on if an injector or other stuff quits after the warranty is out.

Hopefully he can get it fixed, shitty to buy a new truck and have it knocking.

I dont know if an additive would help you out. Something like Lucas upper cylinder lube...or some kind of sulfur replacement/fuel conditioner.

minibike132 · October 27, 2009

Update: No codes, no low injector pressures. Everything checks out from top to bottom. The mechanic seemed knowledgable and honest. We took it for spin cold, and it knocked. After it hit about 100 degrees it started to quiet and then at 180 it quit all together. He definately heard the knock and acknowledged it's there. The fact of the matter is, it's just injector knock caused by a couple of things

1. Ultra Low Sulfur diesel is very dry and has 0 lubricating properties.

2. When LBZ's get watered-down fuel, it usually only takes once to make an injector noisy

He stated that with his experience that the LBZ's seem to be the most tempermental about water induced fuel and the Ultra Low Sulfer diesel is hell on these motors. He told me there is a line of the old 6.5 diesels with problems stemming from it.

I left it with him, he is going to add some additive and run it through. I think it's called Benzanine? Anyway, he said theres a 50/50 chance it will quiet it down. If it does not, he said he will gladly chase down the chattery injector but it's not a guarantee it will ever quiet down.

Have you seen this a lot lately too?

I've noticed it on mine when using ULSD and have had customers with the same complaint. I have never had anyone question the fact that the ULSD is causing it, it's easy enough to figure if you are someplace that still has both.

+1 on water, it only takes once. I have not used any since last winter so I have not checked to see if it will slow down the knock with ULSD but as far as keeping water out I think Howes Diesel additive is the best stuff on the market. I've never gelled and I have a few customers with their own tanks that do not have the best fuel. Once I put them on the stuff we cleared up all the fuel related issues except on a couple that were way too contaminated to deal with using only in tank conditioner.

Your guy is right, he could chase all day and still may never find it, I wouldn't worry about it if it was mine.

desrtrat · October 27, 2009

I'm not up on the newer motors, but don't they have water/fuel separators on them? I'm use to older commercial truck that had them. what we did was check/drain any water from the separator every week, and when we did a fuel filter change instead of filling the filter with diesel fuel, we filler it with Lucas fuel injector cleaner. I'm wondering if changing the fuel filter and using Lucas would help.. some of our trucks had over 450k on them

good luck

Shawn T · October 28, 2009

Update: No codes, no low injector pressures. Everything checks out from top to bottom. The mechanic seemed knowledgable and honest. We took it for spin cold, and it knocked. After it hit about 100 degrees it started to quiet and then at 180 it quit all together. He definately heard the knock and acknowledged it's there. The fact of the matter is, it's just injector knock caused by a couple of things

1. Ultra Low Sulfur diesel is very dry and has 0 lubricating properties.

2. When LBZ's get watered-down fuel, it usually only takes once to make an injector noisy

He stated that with his experience that the LBZ's seem to be the most tempermental about water induced fuel and the Ultra Low Sulfer diesel is hell on these motors. He told me there is a line of the old 6.5 diesels with problems stemming from it.

I left it with him, he is going to add some additive and run it through. I think it's called Benzanine? Anyway, he said theres a 50/50 chance it will quiet it down. If it does not, he said he will gladly chase down the chattery injector but it's not a guarantee it will ever quiet down.

Have you seen this a lot lately too?

I've noticed it on mine when using ULSD and have had customers with the same complaint. I have never had anyone question the fact that the ULSD is causing it, it's easy enough to figure if you are someplace that still has both.

+1 on water, it only takes once. I have not used any since last winter so I have not checked to see if it will slow down the knock with ULSD but as far as keeping water out I think Howes Diesel additive is the best stuff on the market. I've never gelled and I have a few customers with their own tanks that do not have the best fuel. Once I put them on the stuff we cleared up all the fuel related issues except on a couple that were way too contaminated to deal with using only in tank conditioner.

Your guy is right, he could chase all day and still may never find it, I wouldn't worry about it if it was mine.

Thanks,

I have been searching for Howe's retailers on the net and I'm not getting anything but distributers. It doesn't look like any of the mayor parts stores carries it either. Where can I pick me some up?

minibike132 · October 28, 2009

Update: No codes, no low injector pressures. Everything checks out from top to bottom. The mechanic seemed knowledgable and honest. We took it for spin cold, and it knocked. After it hit about 100 degrees it started to quiet and then at 180 it quit all together. He definately heard the knock and acknowledged it's there. The fact of the matter is, it's just injector knock caused by a couple of things

1. Ultra Low Sulfur diesel is very dry and has 0 lubricating properties.

2. When LBZ's get watered-down fuel, it usually only takes once to make an injector noisy

He stated that with his experience that the LBZ's seem to be the most tempermental about water induced fuel and the Ultra Low Sulfer diesel is hell on these motors. He told me there is a line of the old 6.5 diesels with problems stemming from it.

I left it with him, he is going to add some additive and run it through. I think it's called Benzanine? Anyway, he said theres a 50/50 chance it will quiet it down. If it does not, he said he will gladly chase down the chattery injector but it's not a guarantee it will ever quiet down.

Have you seen this a lot lately too?

I've noticed it on mine when using ULSD and have had customers with the same complaint. I have never had anyone question the fact that the ULSD is causing it, it's easy enough to figure if you are someplace that still has both.

+1 on water, it only takes once. I have not used any since last winter so I have not checked to see if it will slow down the knock with ULSD but as far as keeping water out I think Howes Diesel additive is the best stuff on the market. I've never gelled and I have a few customers with their own tanks that do not have the best fuel. Once I put them on the stuff we cleared up all the fuel related issues except on a couple that were way too contaminated to deal with using only in tank conditioner.

Your guy is right, he could chase all day and still may never find it, I wouldn't worry about it if it was mine.

Thanks,

I have been searching for Howe's retailers on the net and I'm not getting anything but distributers. It doesn't look like any of the mayor parts stores carries it either. Where can I pick me some up?

I'm not sure where you are at, I get mine at Farm N Fleet here. Where are you located?

minibike132 · October 28, 2009

I'm not up on the newer motors, but don't they have water/fuel separators on them? I'm use to older commercial truck that had them. what we did was check/drain any water from the separator every week, and when we did a fuel filter change instead of filling the filter with diesel fuel, we filler it with Lucas fuel injector cleaner. I'm wondering if changing the fuel filter and using Lucas would help.. some of our trucks had over 450k on them

good luck

Yes there is a seperator and idealy they would get drained often but no one does that.

Shawn T · October 30, 2009

I'm not up on the newer motors, but don't they have water/fuel separators on them? I'm use to older commercial truck that had them. what we did was check/drain any water from the separator every week, and when we did a fuel filter change instead of filling the filter with diesel fuel, we filler it with Lucas fuel injector cleaner. I'm wondering if changing the fuel filter and using Lucas would help.. some of our trucks had over 450k on them

good luck

Yes there is a seperator and idealy they would get drained often but no one does that.

Located in Pueblo CO. Ag stores are Big R. Maybe there? I have been using the stanadyne the dealer gave me, after 2 tanks of it, I want to try the Howes

Draenor · October 30, 2009

You can use Amsoil's Diesel Concentrate Cold Flow Improver. It will help disperse water from the fuel that can clog injectors. It will also clean and lubricate the pump and injectors.