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Cat Man
Cat Man, Caterpillar Engine Expert
Category: Heavy Equipment
Satisfied Customers: 8861
Experience:  23 Years Caterpillar Engine experience.
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Peterbilt..a fuel filter restriction gauge installed..Im driving

Resolved Question:

Hi, I own a Peterbilt with a mxs in it. I had a fuel filter restriction gauge installed lately and don't know if it's working well. At idle it shows 2 to 3 and while I'm driving it will go up to 4 to 6. Changing the filters doesn't make the numbers lower. Are these normal operating numbers?
Submitted: 6 years ago.
Category: Heavy Equipment
Expert:  Cat Man replied 6 years ago.

Hi. Thanks for using JA! I will try and help you out.


Yes, your readings are normal. Assuming your gauge is registering in HG. You are going to have some restriction on the system as the filters are doing their job.


Is your engine having some problems?

Edited by Cat Man on 10/10/2010 at 2:00 AM EST
Customer: replied 6 years ago.
The engine dosn't seem to have problems, but on long pulls when the boost is high the restiction guage will go up to 7 where the red light comes on the guage. The engine dosn't degrade but I'm wondering if the performance is suffering. This dosn't seem normal to me.
Expert:  Cat Man replied 6 years ago.

Thanks for the information.


The max allowed for maximum performance is 10.


Are you using a Cat Primary fuel filter?

Customer: replied 6 years ago.
Yes, I'm using cat filters(NNN) NNN-NNNNand 1R0749. 10 ? ! Wow ! Why is the light coming on at 7 ?
Expert:  Cat Man replied 6 years ago.

Thanks for the information.

The(NNN) NNN-NNNNhas a 10 micron rating. The 1R0749 has a 2 micron rating. These micron ratings are low in an effort to keep dirt and debris from harming your fuel injectors. I believe that your restriction gauge (if it's like the ones I have seen) was designed for Primary and Secondary filters with a higher micron rating (12 and 25). With a higher rating, the readings would be lower.

Customer: replied 6 years ago.
Thank you very much. You've been very helpfull.
I'll ask the Peterbilt dealer about the gauge rating.
Have a nice Columbus day.
Expert:  Cat Man replied 6 years ago.

Thanks. You do the same.


Please let me know if you need any more help.

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