Need some help guys I have low fuel pressure on my airdog 150 it's running 13psi vp44 truck. The pump is kinda noisy I've checked power 13.82 volts checked my ground and changed the filters and relay and it's a new electric pump got a warranty about 2 months ago was fine then boom 13psi. 

Ok I'll order the ball too. 

2 hours ago, Cummins_Crazy said:

The screen on the raptor the 150 doesn't have that correct? From what I understood earlier was it does have one so I'm not sure. 

You are correct. The 150 does not have the small inlet screen.

I am sorry I caused any confusion, I get AirDog and Rapter switched around at times. Best just to take the male adapter off and look inside the inlet.  I got two RAPTOR 150's 9 mos. ago and they both had the tiny screen which I removed.

 

The regulator on the Raptors now use a different style regulator, no more ball and spring since I pulled one apart and looked at it. It has.... best I can describe... a slide pin and spring.

My old AD100 has the screen. My 2 year old AD 165 4G doesnt have the screen. Me thinks they ditched it for the sake of people's troubles.

Maybe I should just get rid of the airdog and get the fuel boss mechanical lift pump. 

Mine is working better after I took the pump and motor (the whole assembly) completely apart, and cleaned everything with carb/electrical cleaner and put it all back together with the o-rings and bearings lubed liberally with motor oil. Something tells me the electrical motor attached to the georotor or whatever its called, the o-rings in there, put together by the mfg, is the source of the leak. Maybe the o-rings are old, maybe the supplier sucks, maybe they wernt lubed up, maybe the surfaces arent or wernt immaculate.

 

Ive been fighting it for roughly two years now, and this is the first time I've been able to go wide open at half a tank of fuel and not kill the truck or damn near kill it. Lowest pressure I recorded today was 9 psi with my 200 4g pump, that was just below half tank of fuel. 

Curious as to what difference fuel level would make on fuel pressure? 

Edited April 13, 20187 yr by dripley

I could make a video now of it @ less than half tank, go run it WOT, you'd see 8psi minimum, fill up tip-top, shoot again, and you would see probably 12psi min.

 

It shouldnt vary, the same airdog 100 never varied on my truck before my 53 block cracked and I got a new engine from D&J Precision Machine (which btw has smoked oil since day 1), but my new setup has always had pressure fluctuation issues. Been trying to remedy it for a long time now.

 

I've been able to sap the pressure really low, down to zero. Stalled the truck so many times had to buy a new starter. Bled the lines a billion times. Several new sets of o-rings on all banjo bolts, injectors, new injector tubes twice. Had the problems with 50hp injectors DDP 120s and F1 Diesel 220's. Sump or no sump (actually used 2 different sumps). Old harness or brand new harness. New II SO VP or old reman VP (ran identical). Gas cap on or off. Old airdog 100 that always held 15-17psi steady all day, new 165 4g & new 200 4g. Airdog 1 base or Airdog 2 base. Tried three different water seperators and filters 2,6,10 micron.  Three different sets of fuel line. Three return valves, one brand new. Two different sets of fittings across the entire system. The problem was only mitigated somewhat with the higher rate pumps. Further mitigated by running high pressures like 30psi, however I could still drop it down to 8 with a full tank, and say down to 6psi with above half a tank, with the airdog 200. That was a best case senario a wk ago. Now after calling again and them telling me to lube up the rotor on the back side of motor, and having ran each of the three motors various times to say the least, with various different length pressure springs (cut or non cut), different check balls (viton or nylon), I took the motor alll the way apart and put it back together tight but not retard tight, and Im actually able to go full throttle at half a tank or less and not kill the truck with my tune set to Extreme. Odd thing is Im running their "30 psi spring" and im seeing 20psi at idle with the nylon ball. With the viton ball I was seeing 30 psi at idle. Both of those readings /w full tank of gas. That's systematically making one change at a time.

Just finished up with it took all the lines off checked to see if there was anything inside, it was all clean. Took the ball and spring out checked it found another guy said to squeeze the spring where the ball fits so the ball won't go inside the spring father than it should. Put it all back together with some Teflon tape and the pump got quieter and pressure went up to 18 psi. I think I had an air leak on the fuel in line when I took it off there wasn't any pipe dope or Teflon tape. 

That'll do it! Glad to hear it's up and running!

Me too I finish the compound build and can't start tuning due to the fuel pressure now I can start the tuning process. Thanks for all the help and input! 

Sometimes it is just the simple stuff. 

 

 

@rogerash0 no need for a video, I'll take your word for it. Just never heard of fuel level making a difference in fuel pressure. 

Edited April 13, 20187 yr by dripley

5 hours ago, dripley said:

Curious as to what difference fuel level would make on fuel pressure? 

Diesel fuel foams.  So as it's sloshing in the tank, the lower the fuel level, the more chance for that aeration to get to the bottom of the tank and sucked up by the straw.  Then the air compresses in the pump, and while you still have good fuel flow, pressure is lowered due to compressible air in the system.  I've also seen this with a return line that is cut too short and routed into the basket (mine.....) and the same thing occurs.

Edited April 13, 20187 yr by trreed

Which return line? Stock or the FASS?

FASS lol.

2 hours ago, trreed said:

Diesel fuel foams.  So as it's sloshing in the tank, the lower the fuel level, the more chance for that aeration to get to the bottom of the tank and sucked up by the straw.  Then the air doesn't compress in the pump, and while you still have good fuel flow, pressure is lowered due to compressible air in the system.  I've also seen this with a return line that is cut too short and routed into the basket (mine.....) and the same thing occurs.

That is the question. Both my returns go to the basket and I have never experienced it. My normal fill up is around 32 to 33 gallons so I pull mine down pretty low. Can't remember how low I put both of in the basket.

Well it's gotta be damn close to the bottom!

10 minutes ago, trreed said:

Well it's gotta be damn close to the bottom!

I would agree. I hope you will forgive for not checking. Can't find picture of the finished basket but pretty sure I took them into the bottom portion of the basket.

I definitely do not expect you to drop the tank to check that.  

This is my basket.  As you can see, the return line ends right above the stock pump location.  Causes wonky pressure readings below 3/8 of a tank.  Stupid thing leaks so much diesel now that i'm giving up and getting a Vulcan Liberty module at some point.

Edited April 13, 20187 yr by trreed

50 minutes ago, trreed said:

FASS lol.

 

Figured

 

Mines done basically the same, except I think my FASS return line is a little further down, I'll have to find pics to verify. Only issues I get are longer starts when fuel gets below 1/2ish tank when parked on my inclined driveway. That stock return line, like yours is hanging down there, is what I think is causing my issues and I think I'll end up getting a Liberty fuel module eventually as well to get rid of that problem all together.