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Discussion Starter · #1 ·
Recently had my Airdog 4G fail after something got into gearator. Blew a fuse, I fixed that and pump ran a bit until it didn’t. Truck seems to have lost prime after running out of fuel. Ended up getting a warranty pump and replaced. Still cannot start. Seems air bound possibly. Looking for hopefully an easy fix. Any ideas are appreciated.


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So, no screen on the pump inlet? fail install
What is the pressure on the gauge?
Is the pump making pressure at all? the system will not air lock since the return should remove the air
 

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Discussion Starter · #4 ·
That’s what I thought would happen, once pump running, it would recirculate. I hear the pump running but, assuming no fuel is getting to injectors being it won’t start. Only trying for like 15 seconds tops, wait a bit and try again. Didn’t want to kill batteries.


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The pump may not be primed up, you could open the pressure line or if it has a vent and run the pump till fuel comes out -- not good to run the pump dry
 

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HOW MUCH FUEL IS IN YOUR TANK?....IS YOUR PICK-UP FOOT GOOD?....OR DOES THE AIRDOG SYSTEM USE A DIFFERENT WAY TO GET THE FUEL FROM THE TANK?....
 
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Discussion Starter · #7 ·
I sorted it out. I had enough fuel and use a sump. I received a warranty pump from Airdog and followed the instructions provided in regard to only filling the fuel/water separator filter, being the “Airdog will self prime itself, hence filling the separate fuel filter itself.” That, it didn’t not do and was my issue. After filling the larger fuel filter and reinstalling, turning on the ignition switch then jumping under the hood to open up the fuel line slightly, I had some air, then fuel spilled out. Retightened fitting, then was able to fire up the truck after another cycle of switch.
She runs good now. I appreciate the comments here, although I didn’t give much on what parts I have under the hood. I knew air was in there somehow but ones better off without the Airdog instructions. They were great to deal with at the tech line. I probably didn’t need a new pump after cleaning out the debris from gear rotor, but it’s all new now.
I did inquire with Airdog about having some type of filter/protection for the pump and how to avoid another fail, I was told that there should be NO filtering prior to the pump and if so, that could cause cavitation of the pump and is not recommended.
I don’t agree and feel there should be something to protect a $700+ item that’s prone to fail with a sliver of rubber smaller then a pinky nail. But what do I know.
Anyhow, time to sell this truck, my needs require a bigger cab.


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I AM GLAD TO HEAR THAT YOU GOT IT FIXED.....AND SORRY TO HEAR THAT YOU ARE SELLING.....YOURS IS ONE OF THE NICEST STANDARD CAB TRUCKS ON HERE.....
 
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CNH 8940 uses an inline screen with hose connections -- looks like an inline fuel filter, but is a screen -- pick one up at your local Red Iron dealer
 

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To add a bit, and if others have a similar issue, I've ran into similar symptoms and in order to get the pump to prime, I've had to add more fuel into the tank (get it to 3/4 tank) as it was around a 1/4 tank. If your pump is mounted rather high on the frame, more fuel in the tank gives more head pressure to allow flow of fuel to get to the pump easier. Same principal idea of a well pump down in the bottom of a well casing vs a jet pump that is above the water level, it's much easier for the pump to push than it is to pull.

Summit racing has an inline screen filter, and if you really want one, don't get one any smaller than 75micron. As the AD rep stated, a too restrictive pre filter will cause cavitation and pump failure. Fuelab and Aeromtive both suggest the 75 micron or more screen filters for pre pump.

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