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Cat 963b starts good idles up good but is bogging down under…

Customer Question
Cat 963b starts good...

Cat 963b starts good idles up good but is bogging down under any kind of a load

Mechanic's Assistant: What is the complete model and serial number of your machine?

97 model 963b caterpillar serial is 9blo2148

Mechanic's Assistant: Are you fixing this yourself? What have you tried so far?

Change fuel lines rebuilt the filter head on water separator and put a new hand primer pump

Mechanic's Assistant: Anything else you want the Construction Mechanic to know before I connect you?

Not sure what else could be

Submitted: 3 years ago.Category: Construction and Road Equipment
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Answered in 5 minutes by:
10/26/2019
Mechanic: catmastertech, Technician replied 3 years ago
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4,043
Experience: Field service technician for CAT 19 years.
Verified

Hello,

I would replace the transfer pump next.

If you want to be sure that is the issue, test the fuel pressure in the injection pump housing at the test port on the top by the injector lines.

You need 32 psi for a good engine while under load at full throttle. I may go as high as 50 psi without a load at full throttle.

Anything below 25 psi will make this engine weak.

Also, verify you do not have any leaks on the air lines from the turbo to the inlet. A simple boost leak can cause low power too.

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Customer reply replied 3 years ago
Its definitely getting air in the system
Mechanic: catmastertech, Technician replied 3 years ago

Ok, install a clear line at the inlet of the governor housing. If you see bubbles, it is a suction leak in the fuel lines or a restriction. You could also try a fuel supply line to a bucket of clean fuel to see if it is a supply problem.

If that is clear, then install a clear line on the outlet from the front of the engine. If you see bubbles coming out, especially when under load, your injectors are leaking combustion gases and they need to be removed and the cups checked or reamed.

Also, try pinching off the return fuel line to the tank to see if the fuel pressure improves. This may show a weak bypass valve for restricted fuel filters.

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Customer reply replied 3 years ago
Where is bypass valve at on this engineFuel filters are new
Mechanic: catmastertech, Technician replied 3 years ago

Sorry, the test port for this engine is on the outlet of the fuel filter at the tee and line going to the back of the head.

The bypass valve is the block on the inlet side of the filter with the small hose going to the return fuel line. Pinch off this line to test for a bypassing valve.

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Customer reply replied 3 years ago
This engine has 3 filters
Mechanic: catmastertech, Technician replied 3 years ago

It must be modified with a new updated system. That one will not have the bypass line but it will have a bypass check valve in the base of the filter housing with the upside down filter.

You can still pinch the return line off and see if fuel pressure is better.

But, you still need to see if any bubbles are going into the head or if they are just coming out of the head.

The loose and leaking injectors are a common problem.

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Mechanic: catmastertech, Technician replied 3 years ago

I need to step out for a little while. I will be back shortly and can help you further.

Check these items and let me know what you find.

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Customer reply replied 3 years ago
None of the 3 filters are upside down
Mechanic: catmastertech, Technician replied 3 years ago

Ok, that was an interm fix. The later engines had the other version.

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Mechanic: catmastertech, Technician replied 3 years ago

Sorry for the delay, I just got back in.

How has the testing gone? Did you see air on the inlet or outlet? What was your fuel pressure?

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catmastertech
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4,043
4,043 Satisfied Customers
Experience: Field service technician for CAT 19 years.

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