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Caterpillar C-15 ACERT runs rough after sitting 8+ hours?

This question was actually asked to me by another Owner Operator:

I have a '05 ACERT that has about 45k miles on a platinum inframe thru Pete in Grand Island, NE in October '11.

Since the rebuild I've had an issue that three Peterbilt dealerships have been unable to find. All they do is come back to me after a couple of days (my local dealership in Oregon had the truck for 10 days).

The problem is that when I have the engine off for 8+ hours. When I start the engine it runs smoothly, and when I rev it up in neutral its smooth. It's only when the engine is under a load (bobtail, empty or loaded doesn't matter it). I get a severe stutter/miss and it blows blue smoke when I apply about 1/2 throttle or more for only about the first 5-7 miles then it smooths out and runs like a champ.

I've tried letting the truck warm up to operating temperature (water 170-175 degrees, oil to 150 degrees, trans at 150+ degrees before pulling out and it still does it.

I'm thinking maybe? a injector cup? The dealerships have done cylinder cutout tests, fuel pressure tests, and all three have come back to me going "yeah.. it does what you said it did but we don't know why". then wanted to charge me labor for nothing. The engine is still under the 4 year unlimited mileage parts/labor warranty.

Hopefully you can help?

Thanks, Chris

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Chris,

One more thing. If they put the sight glass on and find air, it is possible that one of the six injectors has a bad o-ring. I just saw this on a truck last week with a 3406E Cat. It was actually pressurizing the primary fuel filter with air. Once we cut out cylinder #2, the air disappeared. We pulled the injector and the bottom o-ring was broken. We re-sealed all the injectors and the problem was completely gone.

Keep us posted Chris.

Jeff

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Hi Chris,

Sounds like air to me, yet to be 100% positive what is causing this before tearing in to the engine, there are a few steps I take. The first thing is to install an in-line, clear sight glass on the return side of the fuel system. Second would be obviously connect the Laptop with Cat ET running in "record mode" while monitoring multiple parameters like "injector pulse width, RPM, and throttle position". This way when the problem happens, you can go back after the problem occurs and look at the data stream of how the injectors were performing during the miss. I would zip tie that in line sight glass to the outside of the hood and drive the truck until the problem happened. If the sight glass starts showing bubbles, the tech will know 100% positively that air is causing the problem. If it is air, I like to remove the suction fuel lines, cap them off and pressurize them with shop air. If they are sucking air, they usually swell up and leak air outside too when under pressure. If absolutely everything on the suction side had been checked, the only way to verify if an injector cup is leaking is to pull all the injectors and inspect the cups. Cups leaking air usually show a small black spot in 1/4 of the bottom of the cup. The C-15 injector cups are stainless steel and do not fail often, but it can still happen. I've ran a C-15 for 6 hours once before until this same problem happened while monitoring fuel pressure with a MECHANICAL gauge (not the ECM), and the sight glass method. Once the engine finally acted up, I saw the air bubbles, watched fuel pressure dance all over the place and isolated the suction fuel lines as the problem. When checking for an air leak, also double heck the aluminum fuel filter housing for any cracks or leaking seals. They have been known to leak (suction side) also.

Monitoring the Recorded Data Stream from Cat ET will direct them to an electrical problem (harness, throttle position sensor, injector solenoid, etc.) if that is the case. It just needs someone willing to take the time to test the truck properly and not look for the easy stuff.

Jeff Szarley

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I had the engine harness replaced on Wednesday at my yard due to another issue, and when it was removed the injector side of the harness had alot of broken casing/corroded lines so I was hopeful that perhaps that was the problem. Sadly it was not, and I still have the problem. I have to go thru the yard again soon for a couple other things so I'l have them try a sight glass and see if that finds it.

Thanks, and if anyone else has any ideas please feel free to speak up.

-Chris

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My c13 acert had almost the exact same problem, it turned out to be the fuel transfer pump. It was putting out 15 psi below spec and was enough to cause a really wicked misfire/rough running condition for 5 - 7 miles, then ran perfect. Tim @ NMC in Norfolk, NE is the best!

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I always go to a Cat only shop. They have all the latest updates and seem to be best at setting overhead on these things.

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It could be a collapsed draw fuel line, or a restriction in a fuel line. I had one go like that. It worked fine until I out a load to it, then it would shudder and shake.

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I've tried the sight glass, and found no air. I did recently (last week) checked with another shop in my area and they have a CAT mechanic that's been there for like 20 years. After describing the problem, and the steps I've already taken he's all but sure that it is an injector. And want's to do a cutout test on it when its cold.

He's thinking that the miss i'm feeling is actually fuel knock because one injector is streaming when it's cold. My question is how will a cylinder cutout test help? I used to work on diesels but its been a while. If the cutout test cuts out an injector, will that cylinder just go dead and not cause any miss/unsteady running? Or would it create a miss like you'd have in a gasoline motor if you unplugged a spark plug wire?

Oh and I had every fuel line replaced last month just incase, as well my engine wiring harness (mostly due to the coolant diverter valve wire being corroded, but in the process noticed the injector wiring harness wires were pinched and had some corrosion in the wires cause of it. I was hopeful that between the two it would fix it but no dice yet. Like i said I'm gonna let the guy at the other shop work on it when I'm home next time.

Thanks for all the advice guys :)

Next time I'm home (mid april) I'll take it and park it at the shop so he can have it first thing in the morning.

-Chris

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Wonder what eventually happened here?

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A friend had the same exact problem with a 600 CAT. He drove into Cleveland Bros. at Turbotville Pa for a different problem. The lead service man at that time made mention of the skip after he drove the truck. My friend responded that no one could fix it to date because they did not know what the problem was. The man then told my friend that he knew exactly what was wrong and they would fix it. I have CRS and cannot recall what the issue was. I will find out and let you know.

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It is called COLD MODE that derates the acert as a protection , it's normal if u use fuel temp mod ecm reads 170° temp diesel outside ambient cold water below 160° , its normal

Or check alternator had one dump ac current on negative terminal and ecm files get bad and truck hesitate , check ... Drive without serpentine belt... Thanks if u knew or i m wrong

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Jeffrey Szarley will be eternally grateful.
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