Cat C15 Stumble and Smoking

[Hunter013]

Cat C15 S/N: MXS09731

My driver is saying "For the past couple mornings it has been cutting out and blowing white/ gray smoke out the exhaust. And smells like raw fuel again".

This started a couple of months ago. My driver/ me could not recreate the issue anytime after early in the morning. The truck starts just fine first thing in the morning but, right as he gets on the freeway, it acts up. I performed whatever injector/ fuel tests I could do with ET, no change. I've heard one/ many injectors may leak overnight and give you excess fuel in your cylinders. Is that a thing? If so, how could I find which one? If my records are correct, this motor has
23,558 hours on it and has no signs of slowing down. Any suggestions would be appreciated, thank you.

 

[Truck Shop]

Just wondering are these original injectors?

 

[chidog]

Cat C15 S/N: MXS09731

23,558 hours on it and has no signs of slowing down. .

Then why does it have a problem? That is some high time hours. Never had an inframe or overhaul? Maybe some rings, valves giving up?

 

[Nige]

If those are original injectors @23k they should be on show in a museum for everyone to wonder at……

 

[Hunter013]

I don't know if/when they were replaced, but I really doubt they are original.

 

[Hunter013]

Then why does it have a problem? That is some high time hours. Never had an inframe or overhaul? Maybe some rings, valves giving up?

With the symptoms I gave, would mechanical issues be a problem? I figured because of how infrequent the issue happens, it wouldn't be.

 

[Nige]

Does ET show any Logged Diagnostic Codes or Logged Events.?
Have you done any basic maintenance on the fuel system such as open the tank drain to check for the presence of water/sediment, clean/replace the primary fuel filter/water separator, replace the secondary fuel filter, etc, etc.?

 

[Hunter013]

ET didn't show any codes. The truck has had a couple services since this has been happening. We never saw anything in the filters. We have not checked the tanks themselves.

 

[Nige]

I have no idea what sort of primary filtrer/screen/separator setup it has but it is not unknown for the passages in the filter head to trap particles of dirt. If it looks like the illustration below I'd suggest to pull it off, remove all the plugs and other fittings, and make certain all the passages are clean.

 

[Mobiltech]

I would suggest a complete top end check and adjust. Look for a possible broken injector spring which will usually only show problems at higher rpm.
You could go deeper and pull the injectors to check seals and seats. If seats leak you will usually have hard starting after sitting overnight.

 

[Truck Shop]

Those could be original, 23,000 hours is high. But I have seen one in a 1999 T800 that I use to take care of
with 36,000 hours logged-was still on it's original injectors, piston & liners plus cylinder head. Until it caught
fire and melted the cab off eight months later. Try that with a Detroit or Cummins.

 

[Junkyard]

Some random issues I’ve had with Cat’s….mostly 5EK and 6NZ but as far as I know the twin turbo motors are the same. If you’re getting air on the suction side they’ll smoke and act all kinds of funky. Does it have a spin on primary filter or the older style metal screen setup? I’ve seen the seals on them cause a suction leak.

There’s two check valves (or whatever you call them) in the filter head, they act up from time to time. Also I’ve seen the return on the back of the head leak a drop or two periodically but that’s enough to make them act up and not run right.

Have you checked fuel pressure? Maybe the delivery pump is weak or crapped out. Adept Ape on YouTube did a really good video checking out a Cat fuel system.

 

[Nige]

#2 (bypass vlv) & #4 (check vlv) are what JY is referring to.

 

[Truck Shop]

Does it have a spin on primary filter or the older style metal screen setup? I’ve seen the seals on them cause a suction leak.

I have removed those and reinstalled a frame mounted spin-on for that very reason.

 

[farmerlund]

My 2005 W900 with C 15 smoked and sputtered on initial acceleration when first started. no codes. Once it cleaned up it was fine after that. It was totally random but worse with cooler temps. This went on for a year or two. turned out to be the electronic gas pedal.

 

[Truck Shop]

gas pedal.

Gas? lol. just kidding.

 

[pushbroom]

The IVA's can stick when cold and cause the stumble/white smoke. Once they warm up they straighten up. You can back the IVAs off to .050 then take it for a spin when cold. If it goes away then set one IVA head at a time and test drive til the problem re occurs and replace that head. Usually take 3-4 cold mornings to actually get it diagnosed and repaired. Or just warm it up more before driving with it.
I have had luck with running ATF in the engine oil to help clean out the IVA plungers.
Injectors leaking into the cylinder usually smoke like crazy at first start up.
We have had a couple MXS engines hit 36000hrs before a rebuild with almost all original components.

 

[DMiller]

I changed all the check valves and the fuel return directing valve when replaced the fuel lines on my project truck. Is scary haw fast and easy it starts after sitting two to three weeks.

 

[farmerlund]

Gas? lol. just kidding.

Diesel pedal. LOL

 

[Jelte Steenkamp]

Cat C15 S/N: MXS09731

My driver is saying "For the past couple mornings it has been cutting out and blowing white/ gray smoke out the exhaust. And smells like raw fuel again".

This started a couple of months ago. My driver/ me could not recreate the issue anytime after early in the morning. The truck starts just fine first thing in the morning but, right as he gets on the freeway, it acts up. I performed whatever injector/ fuel tests I could do with ET, no change. I've heard one/ many injectors may leak overnight and give you excess fuel in your cylinders. Is that a thing? If so, how could I find which one? If my records are correct, this motor has
23,558 hours on it and has no signs of slowing down. Any suggestions would be appreciated, thank you.

I would connect ET and check the duty cycle of the pedal with a graph while slowly pushing it down and look for spikes or poor response... simple check.