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2008 GMC Sierra, EFI Live, Airdog 2, 30 over injectors, race valve
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Discussion Starter · #1 ·
I have had issue with low rail pressure for some time. Recently, I had a airdog II 4G installed but hadn’t had the opportunity to tow the camper until this weekend. When I came to a hill, the light came back on and It went into limp mode. The code says “low rail pressure” and sometimes the DIC says change fuel filter. (I have changed the filters and the water separator and cleared the DIC several times). I crawled under the truck with the key on and the engine not running. I couldn’t hear the pump running but it was vibrating slightly. Is that normal? My old fass pump made a lot of noise. I turned the pressure up but it didn’t make much difference. And advise would be appreciated.
 

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I have had issue with low rail pressure for some time. Recently, I had a airdog II 4G installed but hadn’t had the opportunity to tow the camper until this weekend. When I came to a hill, the light came back on and It went into limp mode. The code says “low rail pressure” and sometimes the DIC says change fuel filter. (I have changed the filters and the water separator and cleared the DIC several times). I crawled under the truck with the key on and the engine not running. I couldn’t hear the pump running but it was vibrating slightly. Is that normal? My old fass pump made a lot of noise. I turned the pressure up but it didn’t make much difference. And advice would be appreciated.
Do you have a fuel pressure gauge between the lift pump and filter housing?
If not, I would recommend one.

Also, you should get a scanner that has live data capability like a Tech2.
You need to see actual vs desired fuel pressures
 

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Last year I was on a road trip towing and had an airdog installed getting lowfuel pressure. Pump still buzzing, but took hose loose and was flowing very little. Bypassed pump and ran fine. Got back home and took the airdog off and installed a fleece in tank. I also installed a fuel pressure sensor between the two pumps. Have not towed that large, or for that distance, since installing new pump. Take your hose loose and manually trigger your pump on and observe the flow. It should be spraying as much or more than a garden hose.
 

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2008 GMC Sierra, EFI Live, Airdog 2, 30 over injectors, race valve
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Discussion Starter · #4 ·
I temporarily installed a fuel pressure gauge at the pump and it is showing 10psi. Not sure if that is good or bad. The airdog guy said 6lbs for duramax.
 

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I temporarily installed a fuel pressure gauge at the pump and it is showing 10psi. Not sure if that is good or bad. The airdog guy said 6lbs for duramax.
I would dial the pump pressure down a bit. Too much pressure can cause issues
 

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I temporarily installed a fuel pressure gauge at the pump and it is showing 10psi. Not sure if that is good or bad. The airdog guy said 6lbs for duramax.
My fleece is 12psi at idle at the fuel filter bulkhead, 10-11 while driving. Ive seen it dip to 9 once, lol.
 

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2008 GMC Sierra, EFI Live, Airdog 2, 30 over injectors, race valve
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175 Posts
Discussion Starter · #7 · (Edited)
I was thinking about turning it up some more lol. It is running so much better. Still won’t pull my camper though. I’ve got an appointment at the dealership the 16th.
 

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Last year I was on a road trip towing and had an airdog installed getting lowfuel pressure. Pump still buzzing, but took hose loose and was flowing very little. Bypassed pump and ran fine. Got back home and took the airdog off and installed a fleece in tank. I also installed a fuel pressure sensor between the two pumps. Have not towed that large, or for that distance, since installing new pump. Take your hose loose and manually trigger your pump on and observe the flow. It should be spraying as much or more than a garden hose.
How quiet is the Fleece PowerFlo In Tank Lift Pump? Any problems with it and how many miles have you driven with it installed? Would you buy it again? Thanks in advance, Chris.
 

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How quiet is the Fleece PowerFlo In Tank Lift Pump? Any problems with it and how many miles have you driven with it installed? Would you buy it again? Thanks in advance, Chris.
Sorry for delay. Ive used it about 1.25 years. I'm guessing 15-20k miles. It is no louder than any gas electric fuel pump. Can hardly hear it while truck is running. It was a pain to install because I had to drop the tank, but that should be expected for any in-tank unit. Would I buy one again, so far, yes. I have had 2 airdogs go bad in 5 years, so I wont buy an AD again.
 

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I had the same issue while towing, I had to pull over and reset the fuel filter life to get it out of limo mode. Long story short, the fuel cooler was leaking. Replaced it and zero issues.
 
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