SPN 102 FMI 18

[Neemer]

The subject fault code indicates a loss of intake manifold pressure. I had the pleasure of encountering this code about a week ago on my return trip from Louisville.

I had just refueled and was approaching a turn to get on an on-ramp to I-64. As I approached the intersection, there was a truck ahead of me waiting to turn left. Slowing (engine brake on), I heard what sounded exactly like someone skidding with all four wheels locked up. It was LOUD and I thought someone was going to slam into me. Nope. Then I thought maybe my tag had locked its brakes, but didn’t see any visible sign of that.

Continuing on, I had to have more accelerator than normal to travel at speed, and my engine brake did not seem to have the effect it normally does.

Within about 15 minutes of hearing the noise and on a long Appalachian incline in western VA, the unwelcomed “ding” of a check engine light came on. This is the first one I have had on this or any other coach I have owned. I’ve been blessed and lucky.

We made it home okay and I got it into the local Freightliner shop. This is where the learning begins. I really am a babe in the woods when it comes to understanding how these machines work, but willing and eager to learn.

A small 1” ID rubber 90 deg elbow had blown out. This elbow feeds air directly into the air compressor, the one that fills the air tanks for the brakes and air bags.

Said elbow:

New elbow installed:

I had no idea that compressor took it’s air from the turbo. With that elbow compromised, the entire boost system was negatively affected.

I’m just happy it wasn’t the turbo itself. Like, really happy about that.

 

[Neal]

Glad it didn't require a tow or anything more serious or costly. As we learn from this and from my other post when this came to mind, Cummins service centers are also an option and sometimes when things are more Cummins related I personally would prefer to go to the experts in Cummins servicing. Always learning...

Thank you for sharing.

 

[Neemer]

I read that post and noted that what I’m calling my local Freightliner shop is also a Cummins shop.

Motorhome and RV Service - Excel Truck Group

Is your RV or Motorhome showing a check engine light or DEF light? Are you experiencing loss of power, EGR circuit failures, or failure to regen? Or do you just need your annual state inspection, oil change, and filters changed? Our service team is equipped to handle your biggest RV and...

www.exceltruckgroup.com

I use them on those occasions I need service but can’t wait for an appointment at Gaffney. I’m happy with their results.

 

[Neal]

Great. I use two of the Excel Truck group locations near me too and have had nothing but great experiences with them other than their horrendous backlog of trucks waiting for service. Business must be good in that industry. I picked up some parts for one of them from the Cummins location in my recent belt noise issue and noticed the RV service center that got my attention and a DSDP that was just signing in. Good to learn of the options available.

 

[Neal]

@Neemer any thought in carry a spare of the part that failed? Not sure how often that component fails but seems it may not be an expensive item nor take up much space to carry a spare. I wonder which engines have that? Do you have a part number?

 

[Rich W.]

The subject fault code indicates a loss of intake manifold pressure. I had the pleasure of encountering this code about a week ago on my return trip from Louisville.

I had just refueled and was approaching a turn to get on an on-ramp to I-64. As I approached the intersection, there was a truck ahead of me waiting to turn left. Slowing (engine brake on), I heard what sounded exactly like someone skidding with all four wheels locked up. It was LOUD and I thought someone was going to slam into me. Nope. Then I thought maybe my tag had locked its brakes, but didn’t see any visible sign of that.

Continuing on, I had to have more accelerator than normal to travel at speed, and my engine brake did not seem to have the effect it normally does.

Within about 15 minutes of hearing the noise and on a long Appalachian incline in western VA, the unwelcomed “ding” of a check engine light came on. This is the first one I have had on this or any other coach I have owned. I’ve been blessed and lucky.

We made it home okay and I got it into the local Freightliner shop. This is where the learning begins. I really am a babe in the woods when it comes to understanding how these machines work, but willing and eager to learn.

A small 1” ID rubber 90 deg elbow had blown out. This elbow feeds air directly into the air compressor, the one that fills the air tanks for the brakes and air bags.

Said elbow:
View attachment 27566

New elbow installed:

View attachment 27567

I had no idea that compressor took it’s air from the turbo. With that elbow compromised, the entire boost system was negatively affected.

I’m just happy it wasn’t the turbo itself. Like, really happy about that.

This is actually a fairly common failure, and can lead to much bigger problems if not addressed soon enough. The compressor in these later models gets its air from a 1” hose off the right side (facing from the rear) of the CAC. Since it is benefiting from boost, it requires a smaller intake hose and is getting filtered air from a source (the CAC) closer to the compressor than the engine air filter, so less intake hose.

The problem occurs when that 90° hose elbow fails (maybe a stress point, I don’t know, but it’s where it always fails) because then you loose charge air and thus boost. The compressor still gets enough air, although unfiltered, but the intake looses pressure from a constant leak, rather than an intermittent supply to the compressor, and you have less power and higher head temp.

If you had been watching your boost, you would have noticed that it was low too and the lower boost corresponds with a loss of power requiring more throttle. The problem with that is that you end up with higher head temp because you are adding more fuel without adding a corresponding amount of air. And this is where you can get into much worse trouble if it isn’t addressed soon enough.

 

[Rich W.]

This is my CAC during a pressure test. The blue hose with the plug is where the compressor intake hose connects. The dough-heads at this shop (Floyds in Sidney NE) wanted to sell me a new CAC + a lot of labor, and delayed me about a week looking for one since they are in short supply (I found one in Minnesota and one in Texas), but I demanded a pressure test while I watched, and the CAC was perfect (some leakage is allowable - about 5 psi in 10 min or something like that - mine had none in 30 min). The problem was that little 90° compressor intake hose.

 

[Neemer]

@Neemer any thought in carry a spare of the part that failed? Not sure how often that component fails but seems it may not be an expensive item nor take up much space to carry a spare. I wonder which engines have that? Do you have a part number?

That’s a good idea. It’s clearly something that needs timely addressing by a service truck or garage if not the owner. I don’t know if I could access it properly. Maybe 20 yr ago…

The work order cites Item Nr 609C/4942580 at $46.84.

I guess this is the originators part #:

 

[Neemer]

@Rich W. , that’s a great explanation. Thanks so much for chiming in. I was hoping you would.

 

[Neal]

https://www.fleetpride.com/parts/cummins-multi-purpose-hose-4942580

https://shop.cummins.com/SC/product/cummins-elbow-hose-176743/01tKY000001ziiAYAQ

The Cummins site has the following note on that part, wondering if it's the correct one for your engine?

The Cummins Elbow Hose 176743 is used primarily on Tier 3 3.9 liter B engines.

 

[Neal]

https://shop.cummins.com/SC/product/cummins-elbow-hose-2896482/01tKY000001zinlYAA

The Cummins Elbow Hose 2896482 is used primarily on Tier 3 6.7 liter ISB/QSB engines.

https://shop.cummins.com/SC/product/cummins-elbow-hose-3968748/01t4N0000048etQQAQ

The Cummins Elbow Hose 3968748 is used primarily on Tier 3 8.9 liter ISC/ISL engines.

Your part number may be generic. Something I need to ask about either with Cummins or FL Gaffney. There are quite a few of these elbow hoses when searching the above site.