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Curtis B.
Curtis B., Technician
Category: Construction and Road Equipment
Satisfied Customers: 1165
Experience:  Technican turned service manager with multiple lines of equipment and rental units.
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Second opinion] I have a problem with my trencher machine i

Customer Question

Second opinion] Hi,
JA: Hello. What seems to be the problem?
Customer: I have a problem with my trencher machine i just rebuilt my 3176 (3NL0061) engine
JA: What is the complete model and serial number of your machine?
Customer: when I start the engine everything seems good, however when I put load on it and start to trench extensive black smoke starts to come out and sparks and flames start to come out the turbo, and I bought a new turbo and the problem still persists.
Submitted: 1 month ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 1 month ago.


Looking at you picture of the old turbo, you have an internal failure in this engine and it damaged the turbo.

If you are still seeing sparks, you must still have parts coming from the engine.

Would I assume the engine is not running smooth and has not had any knocking sounds coming from it?

Have you removed the valve covers and inspected the valvetrain for missing or loose push rods?

Have you checked the valve lash or adjusted it anytime in the past?

If the valvetrain is good, I would remove the manifolds and inspect the intake and exhaust ports for signs or the debris that is hitting the turbo.

Odds are the new turbo is destroyed too. Please post more pictures of what you find.

I will be glad to help more if needed.

Customer: replied 1 month ago.
I recently re-built the engine and then I bought the new turbo , I have inspected the injections and they seem ok (attached). But once we removed the 6 injections all of their seals are totally damaged , do you think the problem is from the damaged seals?
Expert:  catmastertech replied 1 month ago.

The bottom seal is designed to deteriorate as the carbon fills the hole. If the upper seal fails, the engine will fill with fuel.

The fuel position does not change much so, the injectors appear fine.

What is your fuel pressure?

What is your boost pressure?

Can you post all the engine pressures and temperatures from ET? Upload a Product Status report as a PDF file if your ET is new enough to have this feature.

Is battery voltage steady? 12 or 24 volts?

Have you inspected the intake or exhaust ports?

Do you have a borescope to look inside the cylinders?

Customer: replied 1 month ago.
I will upload all of the information you have requested.
But, can you please advise how the battery voltage can be the cause?
Expert:  catmastertech replied 1 month ago.

I have seen some ECM's act strange when they have low voltage, near the power off safety shutoff and also at the high voltage shutoff. If you exceed the limit, the engine will stop anyway but, low voltage and high voltage or poor grounds can cause some strange issues. This is very rare though.

If you can, make a video and upload it to Youtube and send me a link. (You can do this with privacy settings on and it should still work.) This would be very helpful to see what your engine is doing.

Customer: replied 1 month ago.
We took the injections to a workshop and after diagnosing them they advised that the nozzles need to be replaced..
Customer: replied 1 month ago.
Do you think that is the problem ?
Expert:  catmastertech replied 1 month ago.

Failed injectors will usually cause a misfire. You stated earlier, the engine runs fine until you place a load on it. The cutout test seems ok.

I have seen injectors cause a slight flutter and run rough under loads but, I haven't seen them cause heavy black smoke.

Fuel service shops must have the very special equipment to test electronic controlled injectors. CAT recommends they never be "POP" tested. Our shop just replaces them when we feel all other issues have been ruled out.

I do not feel I have enough information to say for certain the injectors must be replaced.

The heavy black smoke and sparks from the exhaust tell me you have other issues that would be more likely the problem.

Expert:  catmastertech replied 30 days ago.

Are you still working on this problem?

I will be glad to help more if needed. Please let me know.

Customer: replied 26 days ago.
All the old problems including the black smoke and sparks are gone now after I cleaned the tanks and hoses , changed the nozzles and changed the old turbo with a new one . But I have a new problem now , everything seems ok now but once i start to put load on the trencher machine and start trenching and after 70 meters and half of an hour working the momentum and torque drops extensively.What could be the problem ?
Expert:  catmastertech replied 26 days ago.
Are you sure the fuel tank is clean? I would check fuel pressure to see if it is dropping when engine loses power.
Are you seeing any issues with the drive system? Is the oil overheating? Any warning lights?
Customer: replied 26 days ago.
I cleaned the tank and probably I would need to clean it again . As for warning lights , nothing is showing at all.
Expert:  catmastertech replied 26 days ago.
If you monitor fuel pressure and see it dropping, then something else is blocking the fuel supply and you will know if you need to clean the tank again.
Customer: replied 26 days ago.
it drops, and I bought this machine recently and while I was cleaning the tanks I found a key slot between the two tanks, what is it and it is a reason you think ?
Expert:  catmastertech replied 26 days ago.
No, I can't say I've heard of any reason. Have you pressurized the tank to verify no cracks that may allow water or dirt can enter? Could the slots be for other models as a hanger or bracket mount?
Customer: replied 26 days ago.
The tank seems alright.
Expert:  catmastertech replied 26 days ago.
The tank should also have a vacuum breaker/air filter too. CAT does this with the fuel cap. A vacuum breaker relief and breather filter are part of the cap and prevent a vacuum lock on the fuel system. If the tank does not get air when the fuel level drops, the fuel pressure will also drop. Same applies if the tank builds too much pressure.
Check the cap the next time this happens to see if a vacuum is on the cap or a large amount of pressure.
Customer: replied 23 days ago.
All good . Could the fuel pump be the problem ?
Customer: replied 23 days ago.
because we used an outside tank and the problem is there.

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