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catmastertech, Technician
Category: Heavy Equipment
Satisfied Customers: 2220
Experience:  19 years Cat, 3 years Case
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3116 cat engine in my dump truck how do I turn it up for more power

Customer Question

I have a 3116 cat engine in my dump truck how do I turn it up for more power
Submitted: 7 years ago.
Category: Heavy Equipment
Expert:  catmastertech replied 7 years ago.

Are you sure you want to do this before testing fuel pressure and for air in the fuel? You may have a boost leak in the aftercooler. Could anything else be work with the truck? Is the temperature too high for #1 diesel were you live?

If your set on turning up the fuel you can find the fuel screw between first and second rocker arm group under the valve cover. It usually has a plate held down by a rocker arm bolt. You could back it out one turn. You will need to back out the air/fuel ratio screw also. It is behind the plug on the side of the governor with the triangle shaped recessed area. Back it out on turn but don't turn the stop screw which you will see when you remove the plug. The screw you are looking for is behind the stop screw and just lower than the stop. It may be helpful to plug off the waste gate line from the turbo, it releases excess pressure when too much boost is seen.


Too much boost and/or fuel can overheat and lead to shorter engine life. It will also hurt fuel economy.

These are always the last resort steps when nothing else will work!

Customer: replied 7 years ago.
I had it checked out and the motor is fine it is just gutless.

Do I have to remove the valve cover?
What would happen if I just adjusted the air/fuel ration only?
Expert:  catmastertech replied 7 years ago.
Valve cover does need to be removed. It is hard to get to the rear bolts so, be sure to clean away all dirt before you begin.
Adjusting the air/fuel ratio will help it feel responsive but it does not increase fuel.
other experts are telling me that plug could have a different shape. I work on equipment so, you might see any shape. It still will be about 1 inch in diameter.
Thanks to "danboy72"
Customer: replied 7 years ago.
okay I understand. I will turn both the fuel and air screws out 1 turn. One question I have that someone might know. Is on my 3116 motor the air screw adjustment. I am not sure were it is. There is a cover that looks a little like a freeze plug about in the middle of the injector pump. I think you were calling it a governor and there is a big bolt cover in the top right corner with a twisted wire with a seal on it. It is very easy to remove. so is the air screw under the little freeze plug looking thing or is it under the nut looking cover. Also is it a governor or a fuel pump.
thank you,

P.S. This is the coolest web site
Expert:  catmastertech replied 7 years ago.
I have a picture that will clear it up some. I forgot that some old engines had the freeze plug. The screws on top are for low idle and high idle with the one locked is for high idle.
This unit is only a governor with the transfer pump built into the front drive area. This is the source of the fuel pressure and does not exceed 80 psi normally.

I hope this answers your questions. Feel free to ask more if you need to anything else. Accept this answer if you are satisfied.
Customer: replied 7 years ago.
Now I understand turn the screw under the valve cover clockwise 1 turn. I am still not quite sure which srew on the governor to turn. the one under the bolt cover that is wired and and sealed or the one under the freeze plug looking thing? Also do I turn it one turn clockwise too? I will go on with my project when I am clear on these last things.
Thank You Very Much
Expert:  catmastertech replied 7 years ago.
Turn the screws out (counterclockwise) increases fuel. The cover you are look in for is across from the air/fuel ratio control. This is mounted to the governor with the little pipe connect to it on top. If you follow this pipe it will go around the front of the valve cover and connect to the intake side of the valve cover. This is how the governor feels the boost of the turbo. Remove cover 44 and look inside governor to see the back side of the air/fuel ratio control. The two fingered lever will be hooked behind the end of the shaft from the air/fuel ratio control. It is a pin with a round disc on the end and you can only see the disc. It is not numbered on the drawing. The screw 34 is the screw that holds back the control and this is why you need to back it out(CCW) to increase response. Screw 49 is the high idle setting and has the lock wire run through it. 50 is the low idle setting. The screw under the valve cover is the fuel FULL load stop screw and if you turn it out (CCW) it will increase fuel.
I am sorry for the confusion but, it is a lot to explain without good pictures.
catmastertech and other Heavy Equipment Specialists are ready to help you
Customer: replied 7 years ago.
I wanted to tell you guys on turning up a 3116 cat motor it was like you said but there is not just a regular screw the is a threaded stud with a lock nut and a little allen head hole in the middle of it. i is a littles tricky turning it and holding it with regular tools but it can be done.

The truck runs great with lots more power and no black smoke. Not that I would but what do you think would happen if a person was to turn it more than one turn?
Expert:  catmastertech replied 7 years ago.

One more turn will cook your goose! Don't fix it if it ain't broke.

If you like your results and have lost your fuel economy, leave well enough alone. You want to avoid overheating and melting pistons.


Thanks for the accept.

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