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I just changed my filter in my Air Dog 150. It has been working perfectly. Now it doesn't pump any excess fuel through the return line back into the tank. If I cycle the key, the pump runs...I can hear it and feel it...but it ... JOIN NOW TO REMOVE TRACER

Air Dog - changed filter - losing pressure in return line to tank

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Old 07-24-2010, 04:42 PM
Diesel Enthusiast


Default Air Dog - changed filter - losing pressure in return line to tank

I just changed my filter in my Air Dog 150. It has been working perfectly. Now it doesn't pump any excess fuel through the return line back into the tank. If I cycle the key, the pump runs...I can hear it and feel it...but it pumps no fuel into the tank through the return line. Previously it would always run extra fuel through this return line, I could hear it and see it by taking the fuel cap off the tank. Now it won't do it. I have cycled the key many times. Maybe 1 time out of 10 it does pump fuel back into the return line to the tank, but then when I try it after it won't. Or when it is pumping this extra fuel, if I start the truck it stops ... the truck runs, but the overflow of fuel that has been normal stops, and the humm of the pump changes tone to a lower tone.

Don't understand. I have taken the filters, both fuel and water separator off and checked them. I have removed the gear rotor and checked and cleaned it. Nothing is visible wrong.

Any suggestions?
Anyone else had this happen?
Old 07-24-2010, 09:39 PM
Onemoparnut's Avatar
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I dont know if it is anything like a fass or not but fass told me when changing filters to let the pump run and loosen the filteruntil you hear the humm of the pump change. Then tighten the filter up real quick before it pumps fuel all over.

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Old 07-24-2010, 09:45 PM
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I don't suppose you have a fuel pressure gauge, do you?

Is there fuel in the filters when you remove them?

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Old 07-25-2010, 11:33 AM
Diesel Enthusiast



No fuel pressure gauge. I am going to order one though. And there is fuel in the filters when I rremove them.
I would like to remove the supply line to CP3 and run the pump, with a container. Just frustrates me why this is happening. I am at my inlaws out of town and don't like to mess with anymore than i need to away from my shop. You know what i mean.
Old 07-28-2010, 02:14 PM
Diesel Enthusiast



Gauge should be here today. Looking forward to what it shows. Have called Air Dog twice and didn't get through..
Old 08-01-2010, 09:26 PM
Diesel Enthusiast



Sunday Aug 1
Got my gauge hooked up yesterday. It is burrying itself at 30+ lbs.
So the good news is I have fuel pressure.

Today I pulled the spring and ball that regulates the pressure. They appeared fine. Though the ball stayed in the pump and the spring came out separately.?? is that normal?

Looked it all over and re-installed it. it actually seemed to work well, I cycled the key to engauge the pump and let it run until it shut off. 19lbs. on the gauge the whole time. This held true the 2x's I ran through the ignition cycle, 19lbs. I thought it was just stuck earlier and now was fixed. The 3rd time I cycled the key I started the truck....!! imediately the gauge buried itself on 30lbs. + .....

So the pump seems to work fine. It was pumping fuel into the return line and to the tank like normal before i started it the first 2x's .

So, tomorrow i will call Air Dog again, hopefully can actually talk to someone. Maybe I can just replace the spring and ball and it will be fine??...

Also pulled both filters out again, both are full of fuel. Removed screen from above water separator and cleaned it, though not dirty really.

Old 08-07-2010, 10:26 PM
Diesel Enthusiast



long story short, I replaced my fuel regulating spring and ball. They are in the pump held in behind the return line. I was getting too much pressure, over 30 lbs. I removed the complete spring and ball, without them I was getting about 5 lbs. but the return line was working, returning fuel to the tank.

New spring and ball, I have about 19lbs. of pressure on my gauge.
Don't understand why it went bad and did not look any different than the new one, but now it works,

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