EDIT, I thought I had a AD-100 when in fact I have a Raptor pump unit. Believe its pretty much the same except without the filters. Have changed the thread title to reflect this. ~~~~Installed an Air Dog 100 on my truck last weekend and while its running, its not running right. Am not at all experienced with diesels (am a airplane mechanic) so wanted to post here to see if there is something that I have missed.The pump "seems" to be working fine. I say seems as three times now its "hiccup'ed" on me. Driving normally (not WOT) at about 40 mph or so the fuel pressure dropped from normal levels to 7-8 psi, activating the alarm on my Edge Attitude display. No difference in the way it drove, just lost almost all the fuel pressure. Ok, so I just increased the pressure a bit on the pump (was steady at 14 psi out of the box) to about 20. Well when I did this the damm truck would not start. Have now dropped it back to 16-17 or so and hope that it will start and not do this. I have checked the wiring and its all fine, so do not know what in the world is going on here but am concerned that the pump or motor is going South.A follow up. Adjusted the pressure down to about 17 yesterday trying to get the "hard to start" issue taken care of. Had heard that fuel pressures around 20 or so can make the truck hard to start.Just drove the truck to the store and back. Its getting worse and worse than it ever was. With the stock LP the pressure would stay at 10-12 psi most of the time. At WOT it would sometimes go to 7-8 psi, so I felt that it was time to be replaced to save the VP-44. As well it would ALWAYS start on the first hit of the starter, always.The new AirDog pump on the drive today started off fair, with its taking a bit of cranking to start. Pressure came right up to 16 psi. Drove to the market, about 2.5 miles. Along the way driving at a steady 40 mph the pressure started fluctuating, from 16 down to 7 psi, at an even throttle setting. Came out of the market and it took over 5 minutes of cranking to get the puppy started. Pressure was at 16 at first then dropped down to 10 or so during cranking. The stock LP never did this.Finally got it started and went to the post office. Inside 3 minutes and same thing but got it started faster by moving the throttle back and forth. Once it started the pressure started doing the same thing, going up and down from 16 to 7 psi, and this was at idle under no load. Before you ask, voltage was a steady 13.7. Nothing at all has been changed on the truck other than the AD-100 pump.Hope someone has some ideas on this!Thx,Joe

Where do you have the "draw straw" located??? If it's up a bit off the bottom of the tank, and you don't have a lot of fuel in the tank, you can starve the pump........aka "suck air".

quick! did you mail your warranty sheet in? it is a blue piece of heavy paper.that's what gives you lifetime warranty.is your FP gauge at the VP44 or at the canister? the AD100 should have used the existing draw straw from factory. did you use thread sealent on all fittings?not doubting your skills, just checking basics.if i remeber correctly, airdog said it use the connection off the stock lift pump so it would respond to ecm demands.but check everything easy first.

Thanks for the replies.DW. First off there is no draw straw on this one, its a stock tank and pickup. Vulcan knew that and sold me the fittings to plug into the stock tank fitting on top of the tank. Fuel level is above 1/2 tank so level should not be a problem. Truck was running perfectly with the stock LP on it, just did this to get the pressure a bit higher and preserve the VP-44. Its preserving it all right... the truck will barely start now and the VP will be in perfect condition sitting in the driveway. GW, Second, the fuel pressure output is off of the banjo fitting on the VP=44. Its from a Edge Attitude sending unit. With the stock LP there was never any of this issue, but the pressure was close enough to 10 psi to get me worried. Used thread sealant on the AN fittings but none on the plug in fitting on the fuel tank attachment. We did use the connection off of the stock pump as noted in the AD installation guide. It was a real bear to get to and plug into but its done.Yes that frigging warranty paperwork was sent in a couple of days ago. That policy is pure BS as I bought the pump from Vulcan on the 8th of August and the receipt is dated as such, then they forgot to ship the bio-diesel hose with it so I could not install the pump. Hose arrived well after the pump on 24 August then I headed overseas to work for over a month. I did not even open up the Pure Flow box before leaving so there was no way of knowing that I was supposed to send the paperwork in within 30 days. Am really pissed at this BS way of doing things.Sent them a letter with the warranty paperwork saying that if they were not going to give me the unlimited warranty as I was told by Vulcan to advise me by certified letter so I could return the pump and kit to Vulcan. American Express will reverse the charges if they want to play this game. Did I say that I am really, really, really pissed off at this BS way of hiding the paperwork on the bottom of the box under the pump then putting a time limit on it? Now, just went out and did some more adjustments on the pump. Seemed to remember that there was a 14 psi divert valve on the system so that if the fuel pressure went above that pressure that any excess fuel would be returned to the tank. OK, lets dial the fuel pressure down below 14 psi so that if this valve is sticking or stuck that this might help. Not a bit of help and in fact the engine ran worse with the lower fuel pressure. Right now its set at 12 psi and when I drove it around the block it went as low as 4 psi and the engine almost died. Then looked below the truck once I was back and found the pump had a drip or three of diesel fuel from the bottom. It does not seem to be from the adjustment screw but from the large aluminum plate on the bottom. Am really, really not impressed with Air Dog at this moment. As well Vulcan emailed me back saying that they had received my emails and would be calling me. So far no calls, nor reply emails on what they think that this might be nor how to fix it. All of this after I was talked out of buying a FASS direct replacement pump as "they are not reliable" right now... Well kids, the Air Dog is poster child on my truck for this title right now.Thx,Joe

Flat Twin, Your problem is your AD is sucking Air into the fuel system. This would be on the Suction side of the system, meaning behind the AirDog pump & between the Airdog & The Tank. the 2-most likely sources to check for air is the fittings. Now I just installed the exact same system (AirDog 100) on my truck approximatly 1-month ago. please start w/ that O.E.M Quick connect fitting because I recall when i removed my stock fuel line from fitting on tank that the plastic retainer clip stayed on the tank fitting & I had to clip it off w/ wire cutters. "THIS MUST BE REMOVED FOR THE AIRDOG CONNECTOR TO SEAL TO THE OEM TANK FITTING" check fitting on the supply line at the AD pump use thread sealent or permatex "RIGHT STUFF" silicone in white & black can, or Indian Head sealent its in a small brown bottle w/white cab & can be found at any NAPA. Any sealent will work as long as it is diesel & petrolium resistant. P/S I left my O.E.M. fuel/heater Canistor in place, I installed 1/2inch line between cansitor & VP pump.. No issue run great!!! Hope this will help!! :thumbsup

Had a friend of mine who knows diesels pretty good asked about a possible collapsed fuel filter. Anyone have any ideas on this or other suggestions? Thx,Joe

Hey, Have you called Pureflow and talked to them???? They might be able to help!!!!!! http://www.pureflowtechnologies.com/Contact_Us.htm It sounds like it's getting air somewhere or the pump slows down it's pump for some reason... Have you checked filters for tightness and make sure the drain on the water sep is tight??? Does it only do the drop when cruising at 40 mph??? What does it do at WOT and at idle for a period of time???? It is possible the stock draw-straw/ basket is plugged up!! Did you happen to remove the basket and look at it???? Good-Luck, Winslow

Winslow,No, did not remove anything on the fuel tank, its just too difficult to get to. Did not pull the bed or the tank. The bed has a TransferFlow tank/toolbox in it (too heavy) and the fuel tank was over 1/2 full, so as well too heavy. We just unbolted the bed and tilted it up on the drivers side to get to the fuel tank connections. My question is, it ran just fine with the stock LP pump a few days ago and we have not added fuel or changed anything, so why would simply putting another pump on change anything with the tank or stock pickup? Have not called PF yet, as most of this transpired on a weekend. Will give them a ring on Monday. Frankly I contacted Vulcan as they sold me the unit and have not heard back from them troubleshooting wise. Really thought I would hear back from them on Friday but .....The new thing that does not excite me is finding the drip of fuel out of the bottom of the new pump. This is not a good thing and am really hoping that the pump is not **** up out of the box. Will recheck all the connections but there are only two that I can really get to that have not been checked so far (the ones on the pump are tight and dry), the one on the filter and at the tank. The tank is a bear to get to but will check. Feel that if the connection on the aft side of the filter canister was loose that I would have fuel dripping from that connection. The old connection on the tank had a blue plastic collar that needed to be removed (mentioned in the AD manual) and it was, and is now sitting on my workbench. The new connection with a barb fitting that goes onto the new hose going to the AD-100 pump was supplied by Vulcan and seems to be tight and secure on the top of the fuel tank. The fuel pressure drop is just about anytime you are driving, not only at WOT. In fact I cannot go WOT very much as the fuel pressure just will now allow it. First the pressure drops below 10 psi and second when I reset the pressure to 12 psi on the pump the engine stumbles as the pressure gets low. Thanks for the suggestions...Joe

Update!Talked with the guys at PureFlow this morning and while they were helpful, they as well did not know what the cure to my specific problem was! They are sending me a new pump unit as the fuel dripping out of the pump is not normal and signs of a bad "O" ring inside the unit. Good news is that they have made major changes in their warranty system and purchasers now have 90 days to get the paperwork sent into the company, as well they are now putting a sticker on the outside of the box advising people to complete the paperwork. It seems that there were A LOT of customers unhappy with the old 30 days procedure, myself included.Hopefully the new pump will correct this issue but still trying to figure out why with the old LP pump it would start right off and now I have to crank the engine for a long time. Also turns out that I have a Raptor pump and not a AirDog 100. Still learning...

RBurks,Sorry, did not see your post until a bit ago.Finally got a call from someone at PF that really knows his stuff. Toby at PF sure seems like an expert. His idea was the same as yours but also had about 10 other ideas as to what the problem is. Going to start with the tank connection (yes I did take the blue plastic piece off, and everything is sealed up very well) and work from there to the pump. Seems that there is a small screen in the inlet side that can restrict things, so thats second on the list and so on. We then talked about the bypass valve on the VP-44 (its just behind the fuel inlet connection, so easy to remove and check out. Will report back when I know more. PF is sending a new pump out to replace this one (due to the leak) but several people felt that this would not cause my fuel pressure problems.Joe

Ok... Do you still have stock plumbing between the filter and the VP44? If so call Vulcan and get the big line for between there... As for the wild pressure I would do a lift pump diagnostics. http://mopar.mopar1973man.com/cummins/2ndgen24v/lift-pump-diag/lift-pump-diag.htm While doing the test I would look for flow and air bubbles while the pump is running. If the flow isn't up to snuff or there is air bubbles in the fuel you know to back track and find your air leak.

Ok,Have gotten a fair amount of things done and checked out today.1. Pressure relief bypass valve on the VP-44 is not stuck. Free as can be and nice and clean.2. New fuel filter installed and the old one looked fine. Put the new one in just in case.3. Checked the connection on the fuel tank. It does move back and forth about 1/4 of an inch on the plastic nipple (not the hose on the fitting), not much but is good and snug and on tight to the point that I cannot pull it off. Did not try to release the plastic clips on the hose and pull it all the way off.4. Removed the suction side hose and fitting on the pump. Checked the small screen inside the suction port. Its clean and no debris what so ever.5. As I removed the AN fittings off of the pump, have now put a new coating of pipe sealant on them and will let them sit overnight and cure. Tomorrow morning will probably take the hose off of the rear of the fuel filter canister and put it into a bucket and see what I get out of it. 6. Have re-adjusted the fuel pressure on the pump back up to 17 psi as recommended by Toby at PureFlow. He said that this pressure is a good mix between not overdoing the pressure and having a good margin.I do have the stock plumbing between the filter housing and the VP-44 but a question. The AN fittings on the fuel pump are not anywhere close to 1/2 inch (390 thou ID in fact) so even if I put larger hose and fittings upstream of the pump how is it going to ever pump more with this restrictive fitting on both sides of the pump? If I was hot rodding the truck would probably put these in a lathe and bore them out to get them closer to 1/2 inch but its stock and planning on keeping it that way. Thx,Joe

Another idea is to pressureize the fuel tank with about 1-2 PSI and see if the fitting leak at all... :confused:

Latest update!Pure Flow thankfully overnighted me a new Raptor 100. Had the old one off and waiting for the new one when UPS arrived. New unit was on within 20 minutes. Bled the system, no start. Bled three injectors and it fired right up. Pressure is excellent!Time for a test drive and it works great the first 100 yards. Make a turn in the cul de sac and o'chit man, fuel pressure is right back where it was before, going up and down. Get the truck back in the driveway and bleed the line to the pump... lots of air in the system. Start the truck and it runs fine as before but do another run down the street with the same result. Well guys, we have air in the system, and I have checked every connection there is. My best guess, and its a guess right now, is that the elbow connection to the fuel tank is the source. My option is to hook up a second hose (with the extra fitting thankfully provided by PF) and run it to another tank or source of fuel and confirm this. Ran out of daylight to do so today (thursday) and am busy tomorrow. At least the new pump is not dripping fuel like the old one did, so thats a step in the right direction. Anyone have any thoughts on this? Time to give up and put a drawstraw on the puppy and eliminate this problem? Thx,JoeIn case anyone wants to see a short video of this afternoons fun, its here:

Well, we finally have success! As most everyone said, it was air getting into the system. Where is still not clear but the truck is running and very well at that.Instead of doing a "bucket test" I went a step further and plumbed a long length of hose that I had into the suction side of the Raptor and ran it to a five gallon fuel tank in the bed of the truck. Bled the system (am getting very good at this!) and truck started right up. Pressure was stable at 14 psi, which I then adjusted up to 17 as per several people's recommendation. Out for a drive around the block!It ran excellent and no fluctuations what so ever. Pressure now sitting on 17 and WOT produced a drop of never more than 2 psi, so not seeing anything below 15 psi. Thats what I wanted to see from this pump! Now lets give it a real test. Had one errand to run of about 5 miles. The 5 gallon tank had 4 gallons in it so should be more than enough for the trip, right? Ever heard the phrase "fat, dumb, and happy?".... well I am the poster child for this now.Got to my destination and the Edge warning went off showing low fuel pressure. WTF??? Pulled off of the road and looked in the 5 gallon tank and it was dry. WTF???? O'chit man, the return fuel line! Turned the ignition on and lo and behold the main fuel tank is now higher by about 4 gallons! Fuel went to the VP-44 and what was not used was returned to the main fuel tank! Damm, its empty for a reason. Ok, ran the hose instead into the TransferFlow "Tokyo tank" that is in the bed and got it running and heading back home. Made it 2/3rds the way when it stopped again. This time for good and right in the road. Guess the TF tank is dry.Ten minutes went by while I tried to get more fuel into the system and get it bled on a busy street when a red 2006 Dodge Cummins pulls over and backs up to my truck. He has a tow strap and gets me to a side street where I am safe to work on the critter. Then asks if I need some fuel and give me 3 gallons of red fuel to get home with! Real nice guy. Finally get the system bled, engine started and truck is home again.Called Vulcan and AJ is shipping out a drawstraw and big line (filter to VP) kit. Will give up and drop the tank or pull the bed and do it right. At least we know that the pump is working (and not leaking!) and that where the issue was. Appreciate all the help!Joe

So the stock sender connection was the air leak for sure??? Where the Raptor ties to the stock fuel pickup? :confused:

Mike,Am not 100% sure just yet, will have to pull the bed and look from there but once we eliminated picking up the fuel from the tank the problems went away. My gut feeling is that the "O" ring inside the new connector to the tank nipple is bad, or possible the plastic nipple coming off of the tank cracked.We will have to pull the bed (or tank but its 3/4 full right now) to do the drawstraw, and will be able to give this area a good inspection once we get to this area.Will post back and let everyone know what we find.Joe

Hmmm... It could be cracked nipple or a bad O-ring...So maybe it might be a good idea to do the drawstraw... I gather you going to do the fuel module one right? :confused:

Yes am going with the module unit.

Let me know how it turns out... I've got the old school drawstraw and so far no big problems here I can drive down to 1/8 tank without much issues...