Funny failure mode

[badger_610889]

Hi folks,
I'm been traveling quite a bit for the past couple months therefore I haven't driven nor worked on my trucks much and I've been silent on this forum... I'm about to take off again for another mission and wanted to share the funny experience I just got today.
Day off, spent time with my family and took the M1123 for a ride in the hills. After a while I noticed that the truck starts smelling and smoking whitish and then black. Loss of power about a certain RPM is obvious and I start to worry.
So I stopped the truck and inspected a few usual suspects. You can imagine the psycho - could be the filter, or maybe the pump, or... whatever it can be I need to drive back home.

Note that before I took off a few weeks ago I had removed the fording kit off the M1123 to install it on the slantback (which looks badass with the deep fording exhaust BTW) so I thought I may have messed up with something.

After hours (that makes me look sumb but that's what it took) of investigation including checking the air filter, fuel filter, pump (doing wildass estimate by releasing an injector to see how much it would spray while cranking) I finally found the culprit:

I had improvised a shorter fording by using a section of PVC until Id receive the proposer kit.
It happened that the cap, probably because of vibrations and the suction of the intake, has slid over the pipe and was smothering the engine.

Since all I had was basic tools I took a plier and a cutter blade to bend and cut the pipe so that some clear air flow is always guaranteed:

This doesnt look too good but allowed me to drive back without issues.
What a relief, who enjoys being stuck in the wild because of a failure you don't understand.

BTW I would swear that the truck is more responsive and powerful with the cap at all. Have some of you guys experienced or measured that this cap is restrictive?

 

[Coug]

First time I've seen an ABS pipe extension like that, but about once a year or so someone posts something about the truck having no power under load, and it ends up being that cap sitting down too far onto the pipe.

Glad you figured it out and managed to fix it.
And also, thanks for posting it on here. Not everyone is willing to admit when they are responsible for causing the issue they are having, and it does help others with similar issues.

 

[Sigi]

With the cap off, there is a surprising amount of air flowing at idle. I have wondered how restrictive the cap is at WOT but then I have not seen any black smoke at full acceleration meaning there is plenty of air for combustion.

 

[badger_610889]

Yes this has been trotting in my mind... I wonder as well. I haven't calculated the surface that lets airflow through in that cap but the gut feeling is that it starts restricting at mid range. Turbocharged engines have a better ability to pump thanks to the compressor sucking as much air as it pushes in the intake, but the airflow at the intake of the N.A M1123 baffles me...

 

[papakb]

There's another air choke point in the air intake box that can be opened up to improve air flow. If you remove the intake cap and mounting you'll find a piece called a shield assembly (#5 on the drawing) that looks like a sugar scoop going down into the airbox mounted on the firewall. The clearance between this "scoop" and the housing is only about 1/4" and it's where all the air entering the engine has to pass through. If you remove it and open it up by 1/4-1/2" it will allow more air into the engine without impacting it's purpose.

 

[juanprado]

I was able to obtain years ago reasonably priced from a fellow member here sy-klone air filter precleaner and feel it helps get more air down the pipe. I have no scientific proof just a swag.

I also like how it looks on my fording stack.....

YMMV

Series 9000 Engine Precleaners

store.sy-klone.com