DEF pump and filter.....this time

[Rich W.]

So as some of you know I’ve hade the DEF system blues since Thanksgiving and I finally had my third visit to a Freightliner shop today. First I want to say that the good folks at Sacramento Truck Center really understand good customer service and they went out of their way to keep me informed and help me understand whats going on with this thing.

This time it was the DEF pump. Testing showed it was putting out only .5 psi. I neglected to ask what it should be putting out but I’m certain it’s a lot more than that - probably 100-150psi. So they replaced it and the coach is back in service. And while I’m pleased of course, I’m still not confident in the reliability of the system, and with so many component failures I’m left wondering what’s next.

But a couple lessons learned:

DEF filter - I’ve always read and been told that this has a 200,000 mile service interval. But that was misleading. That’s for trucks that do that kind of mileage in a year or two. Detroit says 3 years max. Mine is approaching 6 years old and I can imagine that in 3 years the paper can degrade, and as much as DEF likes to crystallize, I can easily see it getting loaded with dried urea, especially in a low mileage vehicle. So this is going to be an ANNUAL service item for me from now on and Im carrying one with me. It’s a simple job wit easy access. My part number is 5303604 and they are readily available. A cheap chinese knockoff goes for $11. A Bosch item $40, Cummins $100. Take your pick.

DEF (doser) pump - so this was the faulty part this time, but maybe it went bad fighting a constrictive filter. It’s still under warranty so FL picked up the tab and unfortunately the bad pump had to go back to FL for Sac Truck to get reimbursed. I wanted to do an autopsy on it. But no worries - they go for around $300, not a difficult job, and I’m putting one of them in stock too. My part # 4387304RX.

DEF Header - tested ok this time. It’s the third one on this rig, including the original. It was replaced in Oct 2018, and Nov 2020. I’m tempted to put one of these i stock too, but because they go for around $900, and because they are under continual revision (gen 6 now?), it seems to me that a spare could quickly become obsolete and a regrettable investment. That and my emissions warranty runs three more months. After that, maybe. Part# A04-28402.

Having spares is all well and good but it won’t get you out of derate. You need something that will clear emissions codes for that - not just a good code reader that clears codes. I have the OTR blue tooth J1939 code reader and a one year subscription. The package was $600 and I’ve heard conflicting opinions on whether or not it will clear a de-rate. My best guess from all the sources I’ve consulted is, yes it will, but only after the problem has been resolved. It probably wont buy you time and clear your derate if the repairs haven’t been made. Another option is to spend $1200/year on In-site. But both of these are somewhat expensive insurance and I don’t think I’ll re-up with OTR unless a problem presents itself that will likely be fixed OTR product AND no cheaper alternative exists.

So this is my attempt at a pragmatic approach in dealing with this problem. Given the complexity of the system and the fragile nature of DEF, I don’t see the problem going away, and I don’t see any relief on the horizon from policy makers, as needed and appropriate as that is. Mean time I’m going on a 6,000 mile trip before April 29 when my warranty expires and give it a chance to fail again while it’s still on FL’s nickel. I’ve charted FL service centers along the way and I’ll always know the location of the closest one. Best I can do for now.

Happy travels,
Rich

 

[Neemer]

Interesting. Do you think the pump and filter may have played a role in your Thanksgiving issues but were not addressed?

 

[Rich W.]

Interesting. Do you think the pump and filter may have played a role in your Thanksgiving issues but were not addressed?

Hard to say but you may be on to something. A new DEF header, got me going on 11/25 but only for about 90 miles. Then the system went bad again and I limped back to N. Las Vegas. There on 11/27th (day off on the 26th for TG) they blamed the orig tech for not sufficiently priming the thing, re-primed it, forced a re-gen for good measure and sent me on my way.

That fix lasted about 5000 miles and then on Dec 4, the check eng light came on along with a low DEF warning, but it cleared when I topped off the tank with some freshly purchased DEF. It was in the low 20’s and the DEF was still warm from the store so I inferred that maybe it was temp related. The first problem happened in Nevada in low 20’s temps. But probably (maybe?) a coincidence. Then no more issues until 12/25 when it all started again - this time temps in the low 50’s.

So yes, maybe a failing pump all along, but the DEF header tested bad the first time. It tested good this time which then sent them looking for problems elsewhere. Its interesting that they put a pressure gauge on the pump this time to test it. In all my reading about these issues I’ve never seen anything about DEF pump pressure. They also pulled the doser and watched it squirt DEF to be certain the system was really working rather than just relying on computer testing.

This may sound like over-reacting, but In-Site puts on classes in diagnosing these systems that aren’t very expensive, although the in-site program is $1200.. There is a facility in the east bay and Im thinking about attending a couple classes to really come up to speed on this stuff. It would help keep my rig on the road, I’d be able to help others with these problems, and a better understanding of the system would give me more options for other approaches in the future.

Thanks for this question - I’ve been so focused on the problem at hand, that I hadn’t stepped back far enough to see the whole picture. I think it’s likely that the pump has had an intermittent problem all along. I’ll call Velocity in Vegas and discuss it with them.

 

[Neemer]

I’ve been reading your analysis, logic, and frustrations on this topic for a while now. I think the in-site class would be something worthwhile. If nothing else, you can throw out every question you have ever had about the subject and hopefully get answers. You can’t have too much information on these rigs. People go to Spartan and FL schools. If you have the time and resources, why not?

 

[Calsun]

With my own diesel truck there was one mechanic in 10 that really could effectively troubleshoot the systems, including the emissions components. The rest all rely 100% on error codes and even then the codes are only a starting point. A bad NOx sensor for example can cause the computer to think that something is wrong with the DEF supply when it is actually a bad reading at the sensor.

When catalytic converters and oxygen sensors and MASS devices first came onto the market the failure rate was fairly high. This has largely disappeared with current gas powered engines. DEF systems first appeared in 2011 and so we are still dealing with an evolving technology. If I was going to tow a trailer I would look for a pre-DEF truck but with my motorhome I wanted the current generation from Mercedes for their Sprinter cab chassis.

 

[Rich W.]

Well at least Mercedes extended their emissions warranty. I’ve talked to FL and Daimler about it and of course they aren’t too keen on the idea, but FL is a Daimler company just like Mercedes. I’m not done with this but I admit it’s wearing me down a bit.