no fuel pressure, vp or leak?

Opinions Vary

Opinions Vary

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Oct 18, 2012
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When I turn key to on, Airdog kicks on and primes the line with 12 lbs. When truck starts instantly drops to 10 psi. Before long the fuel pressure has dropped lower and going down the road at 0 psi.

I have put a 30# spring for a 12 valve in my airdog 100. No change

I also put a overflow valve banjo for a p-pump in my vp44. little more psi
 
95cummins5.9 said:
Double check the gauge?
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A lot of people have suggested that and I might try it. The thing is, when the pressure is up, its smooth and always there. When the pressure is down, you can feel it sputtering. So IMO the gauge works fine.
 
Mopar1973Man had me blow the tank. I tried that and found that a decent amount of fuel was coming out of the top of the tank. He suggested an air leak. I have a sump, would an air leak on the sending unit make it harder to pull fuel?
 
Opinions Vary said:
I have put a 30# spring for a 12 valve in my airdog 100. No change

I also put a overflow valve banjo for a p-pump in my vp44. little more psi
Click to expand...


The pressures did not change? I would think there may be a restriction in a fuel line or a problem wit the AD


If the electric motor is running and the gerotor is stationary, pull the center gear off the motor shaft. Is the flat inside the gerotor center gear rounded or missing?

If the electric motor is running and the gerotor is turning slowly, check the voltage to the motor. Low voltage will reduce the motor RPM's; hence, reduce or stop pressurized flow.

If low voltage check the wiring connections and voltage regulator.



Salt is hell on electrical connections
 
Last edited:
Sometimes the seal on.the front of a vp blow out and fill your oil pan with fuel by to much fuel pressure.
 
I would check the wires to the pump motor for fuel. Seal is probably shot & it's time for a replacement.

Ed
 
So i took the bed off to get some easier access. I pulled the lines off and blew air back in to the tank. No results. I pulled the return line of and nothing was being returned. I pulled the fuel out line and was getting a trickle. Dropped both filter and preporator and put back on, no results have been found as of yet. I called airdog and they are sending me another pump. 4th one in a year. So lets see how long this one lasts. This one was junk when I got it.
 
I would sell the new pump and go buy a fass or fuel lab pump. Too many problems with airdog and would be cheaper to buy a good pump than a new vp
 
Water_Lover said:
I would sell the new pump and go buy a fass or fuel lab pump. Too many problems with airdog and would be cheaper to buy a good pump than a new vp
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That is a good idea that I have considered. Yesterday I pulled the cover off the motor and took the gerator pump out. Looked like it may have gotten hot. There wasnt anything to show it was bound up but when I put it back together it ran better than the day before. I turned the key to on and it pushed 8 psi. I started the truck and instantly dropped to 0. I unhooked the return line back to the tank, and tried it again (to observe). I turned the key to on and got a drip out of the return. As soon as i started the truck the PSI dropped to 0 and was pouring out the return line. Now I know that in normal situations it will return a lot of fuel but when it isnt getting enough shouldn't it not return any. Maybe I am looking at this wrong.
 
Hope you find your issue soon and aren't driving it at 0 psi. Hello new VP fass and fuel psi gauge lol


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So hear is an update. VP VP VP I put a brand new airdog on yesterday. Turn the key to on, WTS light goes off, have 12 lbs of pressure, good to go. Start the truck and the fuel pressure drops to 0 in 2 seconds. I put the 12v banjo back in the overflow. I squeezed the AD return line with vice grips and then I comressed the return line form the back of the head. Im guessing this VP is junk. anyone care to chime in.
 
Unless the front seal blew out, the VP would not be the cause of low fuel pressure. Have you check oil level to see if it is high ?? If not I would look for a problem in the fuel pickup in the tank. Try putting the feed line from airdog in a bucket of fuel and see what your pressure is at. Could be another junk pump too
 
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