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Cat Man
Cat Man, Caterpillar Engine Expert
Category: Heavy Equipment
Satisfied Customers: 8812
Experience:  23 Years Caterpillar Engine experience.
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Cat 3116 - Replacing Mechanical Fuel Pump with Electronic

Customer Question

Cat 3116 - Replacing Mechanical Fuel Pump with Electronic

Is it advisable to replace the mechanical fuel pump on a 3116 with a solid state electronic (universal) pump?

If it is something that is advisable... I am aware of the part cost savings, but what would be labor difference between replacing with another mechanical pump vs. an electric?
Submitted: 5 years ago.
Category: Heavy Equipment
Expert:  Cat Man replied 5 years ago.

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


Are you saying that you want to eliminate the governor on the engine and replace it with something else?

Customer: replied 5 years ago.
Yes.. It has been discussed by others (on another site somwhere) that bipassing the mechanical pump and installing a universal solid-state electric pump works like a charm for years and years.

Maybe a little bit of a "rig-job", but on a 14 year old truck, it might make definitely make sense.

You've never done this?
Customer: replied 5 years ago.
P.S. I don't think you caught it, but I put a follow-up question on:

(quesiton is about how to do a visial inspection to verify new lines)
Expert:  Cat Man replied 5 years ago.

I see. I have not seen that before. To be honest not sure how it works.


If you can get some good info on it and they have done them before, it may work fine.

Cat Man and other Heavy Equipment Specialists are ready to help you
Customer: replied 5 years ago.
I'm having a little trouble finding the websites again! I remember seeing something about it 2 different places.

I'll get back to you with links.
Expert:  Cat Man replied 5 years ago.
OK, sounds good.
Customer: replied 5 years ago.
Ok can't find those sites again where people had talked about successfully bypassing the mechanical pump.

I purchased the universal electric pump for diesel (4-9 psi, 35gph), and am going to try it, but I'm having 2nd thoughts about bypassing the mechanical pump/governor. Have you ever heard of someone putting an electric pump between the tank and the first filter before the lift pump, and not touching the lift pump? Is this something worth trying, or will an ailing lift pump still hinder the flow? Something about bypassing the lift pump/governor doesn't sit well with me... even thought replacing it with another pump.
Expert:  Cat Man replied 5 years ago.

I have heard that folks have installed a pump on 3116 engines before but I have not seen it before or how well the pumps did. Sorry.


I would like to think that if a pump was installed between the tank and first filter, it should work fine. I agree with you, not sure if I would want to bypass the pump on the governor.

Customer: replied 5 years ago.
Ok I'm going to try putting it after the newly-replaced plastic line out of the tank, and before the metal line to the filter. Do you know what size the plastic and metal lines are? This pump has nipples on both sides that are made to receive 3/8" rubber lines. If the output is going to a metal line, how would that connect?

What kind of 12V power is nearby this area? Since I'm not bypassing the pump, I can't steal the power from the shutoff silinoid.
Expert:  Cat Man replied 5 years ago.

I would not steal power fromt he shutoff solenoid. This may turn into a problem later on and cause the engine to shut down.


The plastic lines are quick connectors made by GMC. I believe they are 1/2 inch size lines.

Customer: replied 5 years ago.
No that was only if I was bypassing the mechanical pump. Since I'm not doing that, I would not consider stealing power from the shutoff solenoid.

Do you know where I can get or tap into 12V power in that area where the metal and plastic lines come together?

What can be used to convert the 1/2" lines to the 3/8" outlet? Or would a good clamp suffice? I'm going to maybe do this myself if the mechanic doesn't want to do it. I want to know what parts to buy and have ready.
Expert:  Cat Man replied 5 years ago.

I would get the 12 volts straight from the battery or fuse box. I would make sure there is a fuse in the circuit as well. I do not like tapping into other 12 volts circuits because that can cause problems sometimes. If you tap into another circuit, you could cause an overload on that circuit and then blow a fuse.


You should be able to find a good union at a hardware store that will connect the lines if they are different. Most places sell many different size adapters and unions.

Cat Man and other Heavy Equipment Specialists are ready to help you
Customer: replied 5 years ago.
I decided not to bypass the governor and only use an electic pump from the tank to help it out.

What kind of fuel pressure should be coming out of a healthy mechanical pump/governor on my CAT 3116 with a 9GK666** serial? Which end of the high-pressure line is this measured from? (coming out of governor, or going into injector?)
Expert:  Cat Man replied 5 years ago.
The fuel pressure on your engine is normally around 10 psi at idle and 60 psi at high RPM.The fuel pressure is measured after the governor and secondary fuel filter. There is a plug in the line after the filter. This line runs to the back of the cylinder head.