Diesel Exhaust Fluid Crystal Formation

[Goose55]

Was speaking with a heavy duty engine mechanic recently and he said the Cummins 6.7L is one of the best in the world but that it has one major issue and that is the DEF forming crystals which may clog the spray valve and cause major back pressure. He said I would not need to worry about it until a "check engine" light comes on. My problem with that is I live 100 miles from the nearest Ram Dealership, and that would mean driving those 100 miles with an engine/ emisions issue, and that back pressure.

Any ideas ???

 

[TMyers]

The only DEF crystallization would be in the DEF tank at the pickup tube. This occurs when DEF sits and it crystallizes around the tube inlet. These trucks are made to pull and be under a load. Sitting parked and only an occasional grocery run will not use very much DEF.

DEF usage is Post Ignition, it's in the exhaust system. DEF is sprayed into the exhaust causing it to "Stick" to the DPF (Diesel Particulate Filter) grids. As the DPF grids fill with the unburnt exhaust pollutants, there are two pressure sensors, one forward the DPF and one aft. When these two sensors tell the computer that there is a pressure difference, it will trigger a Regeneration. Meaning raw diesel fuel is sprayed into the DPF causing it to "Super Heat" burning the pollutants into harmless ash and blowing it out the exhaust pipe.

DEF is not connected to the Check Engine Light, it has it's own light in our trucks. The message is, "Service DEF System, See Dealer". This means No DEF is following. It could be out, clogged or the pump has quit working. Either way, this will throw the truck into a mileage countdown. (I think it's 150 miles.) At the end of the countdown, the truck will go into limp mode. (5 MPH max. speed)

If you get the warning, pull the DEF tank and clean the pickup tube. If the pump is bad, the Aftermarket folks are making replacements. OEM is or was $1200.

It's not really a complicated system but it is a very expensive system. That coupled with EGR restrictions is why lots of folks delete their trucks.

 

[Goose55]

Thanks, TM. That was really informative. Would you say that when the truck isn't driven much it would be a good idea to keep the DEF tank as full as possible? So that the DEF doesn't oxidize?

 

[TMyers]

Thanks, TM. That was really informative. Would you say that when the truck isn't driven much it would be a good idea to keep the DEF tank as full as possible? So that the DEF doesn't oxidize?

This is one that the RV folks struggle with. Sitting for long periods is the cause. Some of those guys have added drains to their DEF tanks.

Be sure to buy the freshest DEF you can buy. There are posts here on the Forum that show how to read the date codes. Also, I wait until I'm below an 1/8th of a tank before I add more. Keep the DEF in the tank as fresh as possible.

 

[Fuel35 67]

Run distilled water with DEF. I’m not sure what ratio is but it will help with the pump and injector.

 

[Goose55]

Run distilled water with DEF. I’m not sure what ratio is but it will help with the pump and injector.

Sounds like a good idea. But I'd kinda like to know how much distilled water. 50%? 25%? 10%?

 

[Fuel35 67]

I have no clue. But in a pinch, windshield washer fluid and distilled water can get by till ya get DEF.

 

[Travelin Ram]

The only DEF crystallization would be in the DEF tank at the pickup tube. This occurs when DEF sits and it crystallizes around the tube inlet. These trucks are made to pull and be under a load. Sitting parked and only an occasional grocery run will not use very much DEF.

DEF usage is Post Ignition, it's in the exhaust system. DEF is sprayed into the exhaust causing it to "Stick" to the DPF (Diesel Particulate Filter) grids. As the DPF grids fill with the unburnt exhaust pollutants, there are two pressure sensors, one forward the DPF and one aft. When these two sensors tell the computer that there is a pressure difference, it will trigger a Regeneration. Meaning raw diesel fuel is sprayed into the DPF causing it to "Super Heat" burning the pollutants into harmless ash and blowing it out the exhaust pipe.

DEF is not connected to the Check Engine Light, it has it's own light in our trucks. The message is, "Service DEF System, See Dealer". This means No DEF is following. It could be out, clogged or the pump has quit working. Either way, this will throw the truck into a mileage countdown. (I think it's 150 miles.) At the end of the countdown, the truck will go into limp mode. (5 MPH max. speed)

If you get the warning, pull the DEF tank and clean the pickup tube. If the pump is bad, the Aftermarket folks are making replacements. OEM is or was $1200.

It's not really a complicated system but it is a very expensive system. That coupled with EGR restrictions is why lots of folks delete their trucks.

This all sounds nice, but unfortunately DEF is not used in the DPF. It’s used in the SCR.

And OP, if you’re going to start following random internet advice to dilute the chemicals in your truck, I think you’re headed for trouble. One random comment from a mechanic and you’re off chasing shadows.

I, too, have a 6.7. And I take my direction from Cummins and Freightliner. Ram and Cummins stand behind your warranty. Nobody here will give you a dime if you damage your SCR or other parts of the after treatment system following their advice.

 

[tjfdesmo]

The newer trucks will throw a code if you add very much distilled water. Sag2 on TDR tested and proved this.

I pulled my DEF injector at my 40K service, and it was spotless. I also looked inside with my borescope, also clean.

 

[Fuel35 67]

There ya go. But when, not if, you DEF related warranty work and they tell ya it on National Backorder, a diet doesn’t seem like a bad idea.

 

[TMyers]

This all sounds nice, but unfortunately DEF is not used in the DPF. It’s used in the SCR.

And OP, if you’re going to start following random internet advice to dilute the chemicals in your truck, I think you’re headed for trouble. One random comment from a mechanic and you’re off chasing shadows.

I, too, have a 6.7. And I take my direction from Cummins and Freightliner. Ram and Cummins stand behind your warranty. Nobody here will give you a dime if you damage your SCR or other parts of the after treatment system following their advice.

I wrote that DEF was sprayed into the exhaust, not the DPF. The SCR controls how much is injected. Does this sound nicer?

 

[crash68]

DEF usage is Post Ignition, it's in the exhaust system. DEF is sprayed into the exhaust causing it to "Stick" to the DPF (Diesel Particulate Filter) grids.

I wrote that DEF was sprayed into the exhaust, not the DPF. The SCR controls how much is injected. Does this sound nicer?

So how is "DEF is sprayed into the exhaust causing it to "Stick" to the DPF (Diesel Particulate Filter) grids" supposed to be interpreted? Other than it's sprayed up stream of the DPF which ends up in the DPF. The SCR doesn't control how much DEF is injected.
Just admit you have no clue how the DOC, DPF and SCR work within a diesel exhaust system.
The DEF is injected into the SCR and is controlled by the NOx sensors before and after SCR. Those sensors can also throw a CEL P20EE code(SCR NOx catalyst efficiency below threshold bank 1).

 

[Goose55]

e-gads. I had no idea my thread would cause so much conflict. Please, let us get along.

 

[Travelin Ram]

DEF is sprayed into the exhaust causing it to "Stick" to the DPF (Diesel Particulate Filter) grids.

I wrote that DEF was sprayed into the exhaust, not the DPF. The SCR controls how much is injected. Does this sound nicer?

Sounds contradictory, but I’m not really into online debates. The OP and any future readers can decide for themselves what is or isn’t accurate information. There’s plenty of information out there from reliable sources like the companies who build them. I’ve said my piece and won’t be indulging in any more back and forth in this thread.

 

[tjfdesmo]

From an FCA training powerpoint.

 

[Goose55]

From an FCA training powerpoint.

That's neat.

 

[turkeybird56]

That's neat.

delete

 

[crash68]

e-gads. I had no idea my thread would cause so much conflict. Please, let us get along.

No conflict, there's people that just don't know who get corrected.
As for your DEF injector clogging, it's not that big of a job to pull and clean the injector. Warm water is all you need. In some rare cases parts of the injector cage will distort, it's not an expensive part and simple enough to change.

 

[Goose55]

No conflict, there's people that just don't know who get corrected.
As for your DEF injector clogging, it's not that big of a job to pull and clean the injector. Warm water is all you need. In some rare cases parts of the injector cage will distort, it's not an expensive part and simple enough to change.

Warm water it will be then. But would you know where I might find a schematic of the injector cage? I'd be nice to keep in my glove box, with the Users Guide.

 

[crash68]

@Goose55 can't help with a schematic but this should be the correct part for reference.

2013-2023 Ram Injector 4627241AF | TascaParts.com

2013-2023 Ram part # 4627241AF - Injector

www.tascaparts.com

Sometimes the face can build up crystalized DEF, If I remember correctly the injector is just a simple 12V On/Off but usually just need to clean the face off.