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Curtis B.
Curtis B., Technician
Category: Construction and Road Equipment
Satisfied Customers: 1169
Experience:  Technican turned service manager with multiple lines of equipment and rental units.
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I have a Cat 235 BLC excavator that billows out black smoke

Customer Question

I have a Cat 235 BLC excavator that billows out black smoke from the exhaust all the time when running iat full throttle
Submitted: 2 years ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 2 years ago.
Hello, I am sorry no one could help you earlier. I will be glad to help you if you still need it.Can you post the full machine serial number?Have you checked the turbocharger and lines for boost leaks and manifold pressure?Inspect the engine for a small boost line to the back of the fuel system Air Fuel Ratio control. I have seen the tube crack an cause loss of boost signal to the control.
Customer: replied 2 years ago.
I have heard that and will have our mechanic check that also I will get the serial number for you
Expert:  catmastertech replied 2 years ago.
Ok, thanks. Let me know what you find and details about how this problem began. (previous problems and recent repairs)
Expert:  catmastertech replied 2 years ago.
I may be out during the day but, will answer back tomorrow night. (US Eastern DST)
Customer: replied 2 years ago.
Our mechanic still has not checked the excavator and I will keep you posted
Expert:  catmastertech replied 2 years ago.
Ok, keep me posted or the question may go dead.
Customer: replied 2 years ago.
Sorry it has taken so long to get the Serial 1987 Cat 235BLC, SN# ***** and the Engine is a 3306
and the Engine Serial # ***** *****
Also I had our mechanic check the small boos line and he is telling me that this engine does not have one.I will wait for your responseAngelo
Expert:  catmastertech replied 2 years ago.
Thanks for the serial number. Just to update your information, the machine serial number returns an engine serial number of 08Z39349. I did confirm this engine does not have an Air/Fuel ratio control or lines. I would next focus on the air supply to the engine. Black smoke is normally not enough air for the fuel to burn. The first thing to check is the air filters, remove them completely to verify they are not plugged. I have seen a few look ok but, still be to restrictive. Inspect your precleaner as well, wet conditions can cause these to plug also.Inspect the turbocharger lines for boost leaks. Check the turbo shaft for excessive endplay and dragging internally.Look for signs of oil leaking into the intake of the engine from the turbo. If you have tooling, measure the turbo boost to the intake to see how much pressure the turbo can supply the engine under load. You should get close to 15 psi under a stall load.Another item that is missed on these engines is the valve lash. These engines will wear the adjustment ot of a normal range and should be adjusted every 2000 hours. If the valve lash has not been checked, perform this adjustment on a cold engine with .015" intake and .025" exhaust lash settings.The next item I would check is the timing. This will require a pin tool for the injection pump and a 3/8" bolt for the flywheel. The tool is available from your dealer if needed. I turn the engine to set #1 compression and lock the engine with the bolt in the flywheel and then check the pin timing notch on the injection pump. If the pin notch is more than half off the hole, then timing should be adjusted. If less than that, you may rock the crank back a little to see if it will catch and then stick the bolt back into flywheel. If both will go in together, timing should be ok.The further down the list we go will become more involved and require some repairs. If you have done any recent repairs, please let me know the engine's history and I will be glad to narrow down some other issues.Just let me know what you find and if you need further help.
Customer: replied 2 years ago.
OK, thank you for the info and I will have our mechanic go over these item to see if it will improve the performance,
I will keep you posted of our results.
Thank you so much for your helpAngelo
Expert:  catmastertech replied 2 years ago.
Ok, I will be looking for your reply.

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