Airdog

[SOOT4BRAINS]

I have had an airdog for about 10 months now.... unit has been on the truck for 9 months now.... Been hooked up and working for 2 days... I used the draw straw they give you with it, and put in a return line to the fill tube. Also got a 15 psi relief spring for it. When I FINALLY got my fuel pressure gauge, and fittings I hooked it up on Friday. At that point I had about 3 gallons of gas in the tank (had it almost empty in case I needed to drop the tank, it would be light). After firing it up, the fuel pressure would bounce around from 15 to 17, and you could hear the relief valve making a funny noise (with engine off). I went straight to the gas station, and put $20 in it. When it was almost empty, fuel prssure would drop to 2-3 psi from the slosh when I would brake. After I put some diesel in it, it doesnt drop past 14 psi, but it still did the fluctuating from 15-17psi and noise is still there. Would have tanked it, but I'm poor..... I am pretty sure it is sucking in air through the draw straw. Not a lot, just enough. If I let it sit in the driveway for a couple minutes, it gets to 15.5 psi and stays there. I want to try one of these http://www.vulcanperformance.com/Draw-S ... -p/dsi.htm , but not sure if it will work. Does anybody know what the diameter of the spare bung on the fuel sending unit is? Then I will use my stock lift pump (or maybe a 2nd gen lift pump) to fill be fuel "basket" up, and put the airdog pickup in the basket with the airdog return also pumping back to the basket. Then the aidog would always have fuel no matter the tank level. What do you guys think? Thanks!!

Aaron

[Oddfire]

.... I hooked it up on Friday. At that point I had about 3 gallons of gas in the tank (had it almost empty....

[skilletky]

my FASS does the same thing below 1/2 tank. now i feel better knowing i aint the only one with this problem. i am still using the stock pick up. it only does it when i brake or accelerate hard so i think it is just getting a lot of air in the system. when i got to drive my truck it did not seem to affect the engine, but that was only for about 4 miles hopefuly when i get my second trans , i can see what the truck really can do

[SOOT4BRAINS]

.... I hooked it up on Friday. At that point I had about 3 gallons of gas in the tank (had it almost empty....

You should have heard it running and what the pyro did when I hammered on it....

No, I have not put gas in it yet instead of diesel, but my mom put gas in our old '80 240D benz one time. That was not fun. I am going to drop the tank I guess and measure the bung, then call vulcan on tuesday and have them measure the fitting. I wont be happy until my airdog is full of fuel and not air.....

[PToombs]

I would put the pickup more towards the rear, and definitely not in the basket. The fuel dropping back into the basket will aeriate (i know i spelled that wrong, and the wife lost the dictionary ) the fuel, and you'll get more problems.

[SOOT4BRAINS]

Interesting thought. What if the return lines were plumbed down below the fuel level in the basket? not to the bottom by the pickup, but down below the full level. Same idea as when you put your garden hose under the surface of the water vs. above the surface. Maybe it wouldn't aerate so bad? I filled up the tank tonight, with DIESEL and the fuel pressure is still fluctuating some, but its slower now. It takes it 10-15 seconds to build up to 17, the drops fast to 15 again. The slosh problem is gone though. Just when its below about 1/3 tank it sloshes and pressure drops to 2-3 psi then jumps back up real quick. Oh, and the pickup is located by the factory sending unit. I didn't really have a problem with pressure while accelerating, only braking, so moving it back won't help much with slosh I think. Or am I missing something? Thanks for the response, keep the ideas coming. I really want to get this thing reliable, and want to use my whole tank of diesel too.

Aaron

[PToombs]

Dropping the fuel in below is better, that's how the factory stuff is plumbed.
I've seen other posts where guys had slosh problems. I think the AD and FASS moves so much fuel that it's prone to it when the tank gets below 1/2 or so.
Try it inside the basket and let us know how it does.

[SOOT4BRAINS]

I had one pressurized fitting that was seaping just a little bit, so I pulled it off, and put some thread sealer on it, also took the regulator spring out and made sure all was clean inside. Checked all the fittings for leaks on the drawstraw to the pump line to see if it is sucking in air that way. Even with a full tank, and sitting in the driveway the pressure still goes up to 17 then drops to 14-15. When it does this, you can hear the valve doing something. I am pretty sure its not getting air in the lines. I'm going to call pureflow tomorrow and see what they say.

[SOOT4BRAINS]

I just got back from a drive. I had to wait for results of my last tear down and reassemble of the fittings due to the thread sealer drying. It does what it is supposed to do now. 15.5 psi very steady. Can pull down to 14 at wot. That funny noise it was making when the pressure would drop, it does that non stop now. It is pretty loud. Can't hear it with the engine running though. The motor on the airdog is quiet. The return valve is what seems to be making so much noise. I have the unit rubber mounted, so I cant hear or feel it inside, but outside its a loud fast pulsating noise. Still going to call tomorrow to see if this is the norm.

[PToombs]

Let us know what they say. I think I read someplace that that noise is normal. Steady is the key, sounds like you fixed it.

[SOOT4BRAINS]

Called pureflow this morning. He said it may just be normal operation noise. He said excess noise is usually a restriction some where or air in the lines. He said to take the line off the draw straw and stick it in a bucket filled with diesel and see if it still makes noise. Maybe the draw straw sucked something up? I have good flow and pressure. It's coming from the return valve. If you touch the motor, input line , output line or fittings, its just feels like a little hum. If you touch the return line, you can really feel the vibration in the line. I don't think I have a restriction as I have 1/2 line all the way from the tank to the pump. I may try bucket test this weekend.

[GLHS]

Yours and mine do the same thing. Worked perfectly for about 3 months but, gets worse everyday. Now it will spit and sputter with a nearly full tank of fuel.
I have a custom made soldered together 1/2" copper tubing for a pickup.
It does not matter what we run for a pickup; they will never work right with the pump mounted so high.
I talked about this about a month ago in another thread.

The partial solution would be to use Joe Hellmanns tank sump it will probably rid you of 80-95% of the problem.

The correct solution would be to mount the head of the pump as low or lower than the bottom of the fuel tank; just like all electric pumps in factory fuel tanks made in the last 20 years. I am thinking of doing this knowing my filters will be hanging waaay low. Oh well!

[SOOT4BRAINS]

I thought about the sump pickup too. This will also help with the 1/3 tank slosh issue I think. I think the noise is from restriction, and that restriction is sucking from the top of the tank.... I am not too concerned with stuff hanging down, now that my truck is painted I dont even take dirt roads unless I absolutely have to. If it was 4x4 maybe, but it not so its a road queen.......

[SOOT4BRAINS]

Where were you going to put the sump setup at? I was thinking towards the middle near the factory pickup. If its in the back, when you go down a hill, it may run out and if its in the front then on hard acceleration or uphill it will run out of fuel. Of coarse this is all at low fuel levels. The sump looks fairly big, so it will hold a little fuel while it is sloshing at low levels, I just wonder how long the fuel in the sump will last with a 150 gph pump sucking it out. With the draw straw, when it sloshes, I am never at low pressure for more than 3 seconds or so. I think this may be the ticket to solving this.

[seeker1056]

you will find that no electric pump likes to suck fuel - they were designed to push fuel even if the manufacturer says otherwise

Yuo will also find that the screen in the tank for the pickup causes issues too - again because they dont like to suck.

we chased this kinda stuff for a whole season through several pumps, fittings pickups etc etc

setup that worked for us finally was a course fuel filter on the end of the pump, no in tank filter, tank sump for a supply, pump mounted lower than the tank and a really good filter after the pump and very large lines

If your usin clean fuel and your system was clean to begin with there is no fear of hurtin the pump by not havin an in tank filter