Fisherguy

I've been following lotsa threads about lift pumps on here and was convinced the Airdog 100 would be okay if I used the Liberty canister and plumbed it's return into the filler neck. I WAS WRONG!
I did the install on the weekend, put it all back together and with 6 gallons of fuel in the tank I started it up, the fuel pressure gauge showed 13 pounds but would drop to 0, then up to 13 and kept bouncing around like that. I went and put another 4 gallons in and this had no effect, the gauge kept bouncing from 13 to 0 to 13 etc. I was convinced I had a leak on the intake line somewhere.

I thought I had a leaky fitting where the line attached to the canister, and since I couldn't get it off I had to drop the tank. I still couldn't get the new AD fitting off and after getting the compressor involved I was convinced there was no leak there so I pulled out the canister to investigate. With the canister in my hands I decided to try a little experiment so connected it to the pump and immersed it in a 5 gallon pail of fuel. I got a rock steady 13 pounds at idle, when I lifted the canister out of the fuel and it's level in the canister started to drop I could see my FP gauge would drop to 0.

Then I plumbed the engine return line so it would pour into the canister trying to simulate what was going on in the tank, same result though. The engine return at an idle is practically a dribble, the AD draws fuel out way faster than the engine return is pumping fuel back into the canister.
This tells me what's going on at an idle is when the fuel in the tank is below the level of the top of the canister and the AD keeps sucking it out it'll reach a point where the AD is sucking air and the FP gauge drops to 0, the engine doesn't stall or stumble though as the CP3 is able to draw from the AD's filter until eventually the engine return has put enough fuel into the canister that the AD is able to get suction, the gauge jumps to 13 till the fuel in the canister drops and the whole thing continues.
After that I went an put in a half tank of fuel, got a solid 13 pounds pressure until last night when, with just over ¼ tank of fuel I was going down a steep hill and started getting the bouncing FP gauge again. Now the more I drive it with less fuel in the tank the more bouncing I get.


So I think I have 3 options:
1) get rid of the Air Dog and install a Raptor 100 instead. It pumps the same volume but only supplies the engine with the fuel it needs, there is no bypass to worry about, Now I wish I went with the Raptor instead.
2) remove the AD and return everything to stock (not gonna happen)
3) drop the tank and plumb the AD return into the top of it to keep it full of fuel which is what I'm gonna do. Doing this kinda irks me off cuz my whole reason for using the Liberty piece is so I wouldn't have to mess around modifying the tank and/or the canister with new draw straws, fittings etc.

So my advice for anyone considering the Liberty unit with their new pump is to not bother, save yourself some money, just remove the stock pump from your existing canister and plumb the Air Dog return line into the canister like Mark (53 ******) did. I'm going to use a draw straw with bulkhead fittings though rather than relying on the one the AD comes with that uses an o-ring as a seal, I don't trust that and don't want to be dropping the tank again (for the 6th time!) to fix another leak.

Charlie tells me the AD 100's are coming out with the wrong pressure spring and will be sending me the proper one in the mail. He says the pressure should be up around 17 pounds.

So far the 'actual' AD works great though, I get 13 pounds at idle and when I run CL I can only draw it down 3 pounds to 10 psi, it's quiet and seems like a slick unit. I used the Raptor bracket for the install so it mounts parallel to the frame rather than perpendicular to it. I put it just behind some bracket that sticks out on the top of the frame just behind the skid plate for the transfer case, it's well protected there and I'll do another thread with pics on the install this weekend.

Tother handy thing with the AD is if you need to drop the tank you can pull the return line off the filler neck and have it pouring into a fuel can so when you run the engine the excess fuel is pumped from the tank making removing and re-installing the tank a lot easier. It's not a constant low though, when the gauge shows 0 you won't get anything going into your gas can.

I'm getting pretty good at dropping and re-installing the tank though, I had the canister back in place, tank up and refilled with the truck running in 90 minutes on Sunday (with only hand tools)!

trx

Dont you hate it when things go like that? I too have 1/4 tank issues with my pump but gave up trying to fix when i realized i would have to drop the tank again, wow 6 times you are motivated. Hope you get it all figured out i may return under my truck and try using the stock canister instead of the draw tube if that gets rid of the 1/4 tank problem.

Fisherguy

Only 4 times so far (had a problem withthe vent mod too), 5th will be to mod the canister, 6th would be if I used the draw straw with the o-ring to fix the leak!

Langley eh? You buy your Walbro locally? if so where? (I'm wondering if they'd have a draw straw?)

53 willys

just plumb the AD return to the canister and see how that works..sorry for your troubles Will

trx

Sorry cant help with draw straw bought my pump from glacier diesel online. What happened with the vent mod i may try this one to get back what i lost due to 1/4 tank issues.

53 willys

Dang Will I feel bad I am about ready to send you my modded canister!!! or you can send me yours and I will mod it with the summit bulkheads??

Fisherguy

No problem Mark, hopefully this will save someone else the frustration!
B'sides, spending an afternoon tinkering on the truck in the shop while enjoying a couple tastey beverages with the tunes on aint such a bad thing...


TRX, when I did the vent mod I accidentally poked a little whole in the tank with the screwdriver when I was removing the ring around the canister. I went and filled up and had a pretty good drip happening!

We dropped the tank and did some plastic welding using a soldering iron and the little piece of the tank that was in the hole saw from the vent mod, worked great!

Fisherguy

lol
Really Mark, it's not your fault and I appreciate all your help and advice.

I'm sure I can grind down the canister with a dremmel and mount that draw straw okay myself. Shipping the stock canister down there and back would probly cost more that just getting a new draw straw and doing it myself and it shouldn't take me more than a few hours.

Was thinking of this fitting, but it's made for 3/8 hose instaed of 1/2", would also like to have a fitting I can undo at the tank like the AD ones so I can take the hose off without having to cut it, any suggestions Mark?
http://www.glacierdieselpower.com/pr...px?pf_id=14FPA

Only thing I'm thinking is the plastic of the canister is pretty thin, grinding all those ribs off will make that part of it pretty weak but it's not like it's going to be sitting anywhere it should get whacked by a rock or anything...

Sandaholic

I just fell asleep on the couch watching a movie and couldn't sleep after that. Anyway this is the first time I've read this thread. Almost made me kinda sick thinking about the frustration you were going through. I bet the F-bomb was dropped a few times? Man that really sucks. You get it figured out yet?

If you go through that modded liberty module thread I started, you'll see or read rather, that I used a tee in the return line from the airdog to the canister. It has a regulator after the tee fitting (got it from vulcan). So the airdog return is constantly filling that cup up and you reach a point where the pump is putting out too much volume for the restrictions in the top of the canister so it backs up and then finds its way out through the reg. into the filler neck.

I also changed the purpose of the inlet and outlet on the top of the module. The outlet or old supply to the cp3 became the return to the canister (it's larger and I figured it would fill the cup quicker). The old return port stayed the same basically. It now dumps freely into the tank as I had removed the old supply tubing and switched the return hose on the underside of the module.

If you did that you shouldn't have to drop the tank again. You would just add some fittings at the framerail. I'm not sure if it would work as well though in your case. You would add your tee in the return line to the filler neck. The filler neck line would be regulated and the bulk of your flow or the initial unregulated amount would be filling the cup. It would go through the smaller of your ports on the top of the canister instead of the larger one. Now Marks way is fine too. You just have to drop the tank again. I actually like marks way cause you don't have to mess with the regulator. I came up with my fix though cause I didn't want to drop the tank again. 4 times would take some serious dedication.......I'd be lookin' for a grenade

Sorry if this didn't make sense.

06trx

I did the airdog 100 last weekend. I did the draw straw and the filler neck return. Last night filled the truck up and put in 28+ gal. ,I was holding my breath the last 10 mi. or so. My guage never droped below 10psi.

Fisherguy

I'm gonna drop the tank and modify the canister by putting a draw straw in so the AD return is constantly pouring back into it, this is what I was trying to avoid, oh well!

I'll still be taking the fuel out using the stock canister supply which is okay with the 100.


06TRX, are you seeing 10 psi all the time? I get 13 but according to Charlie that should be 17 and I'm getting a new spring sent to me to bump that up.
I can't draw it down less than 10 now though, that's good!

Fisherguy

BTW, after filling up yesterday I noticed a small drip off the fuel tank, I figured maybe my vent hose was loose. When I got home I removed the fender liner to have a look, the vent hose was dry but the area around the canister was wet with diesel.
Thats when I discovered the factory fuel line I'd taped up to seal was dripping fuel there. I guess the filter housing is higher than the fuel tank and it was leaking past my tape.
I drained the canister and removed the tape on the hose going to the CP3 (I'd removed the factory steel tube to the banjo bolt).
I then blew out the factory line to get all the fuel out of it and re-taped both ends so I shouldn't have any dripping fuel anymore.

Festus

Fisherguy,

I'm sorry you've had all this stress with you're install - just count to 40 instead of ten and have another beverage!

In *****'s thread, if I may paraphrase, you kind of asked why I'm going to the extremes that I am for my AD150 install. Answer: I am only lifting the box off once!! There is alot of stuff I want to do with my install, and I plan on only doing it once.

Good luck with the rest of it.

COWBOY6300

When I Did My Airdog 150, I Used The Drawstraw And Put It At The Back Of The Tank, Have Never Had A Problem, Run It All The Way Down Until The Over Head Doesnt Give Milage To Empty, Says Lo Fuel, And Light Flashing

53 willys

whats your fuel pressure gauge say?? and what about when you go down hill??