I have a 98.5 24v with the airdog 150 with the 1/2 lines and draw tube. When i go to start it up in the morning it has problems starting sometimes. If i cut the power to the LP pump while cranking or before i crank it, it will start. The fuel pressure reads fine. I have replaced the vp44 for this reason and nothing changed. It used to only have hot hard starting issues, but now just cold. Could the diaphragm be damaged in the pump, or just too much pressure when cranking on the vp44? PSI is around 5 to 8 depending on how long it was cranking. 17 PSI when running. I also found that my truck only like to start after the wait to start light goes off. My light always comes on, no matter how warm it is. It will only stop working once the intake temp senor gets dirty from my edge ez. I then just have to take it out and clean it. I have been fighting this just by cutting the power to the LP with a toggle switch on the dash and has been working great. If i have to get another vp44, id like to get the hot rod and get rid of the edge ez and just use a boost fooler.

 

Do you have the AirDog wired right. Because you do not want the AirDog pump running when you start. The Vp44 wants no fuel pressure at the injector pump for starting this is controlled by the ECU and the relay to the AirDog


The AirDog™ is equipped with a relay controlled wiring harness that connects directly to the battery and is activated by the OE fuel pump connection. Optional "low fuel pressure" warning light is available.

6 - 1 Connect the RED lead to the POSITIVE (+) post of the driver's side battery. Connect the GREEN lead to the NEGATIVE (-) post of the same battery.
6 - 2 Route the wiring harness to the AirDog™ and connect the 3 pin Deutsch connector to the corresponding connector on the AirDog™.
6 - 3 Secure the relay to the vehicle at either the engine side wheel house or firewall near the steering column.
6 - 4 Disconnect the OE fuel pump lead from the ECM connection (Deutsch, two pin connector).
6 - 5 Connect the AirDog™ 'Relay activation lead' to the OE fuel pump ECM connection

 

The factory lift pump runs when cranking. If you ever ran it out of fuel you'd have a hard time getting it started, but you the first person to suggest that to me. The Fass has instructions on how to wire there pump to the window circuit. The windows don't work when your cranking.

 

i'd double check to make sure the grid heater is actually heating. i just removed my custom intake becuase i was only heating half of my intake air, and it started horribly. put the stocker on and she fires up like a champ.

 

Hard starting when the engine is cold or has been sitting for hours is an indication of a leak in the fuel system. Most likely in the return side too. Parking the truck with the nose downhill overnight will help it start if thats the problem. Common areas of leaking are the injector o-rings, the banjo on the back of the head, and the T fitting just below the banjo. Also, if one or both of the batteries is bad then hard starting cold can arise.

Hard starting when the engine is at full operating temp is an indicating of the fuel pump over pressurizing the VP during cranking (which can be determined by unplugging fuel pumps fuse), or the VP's computer giving signs of failure (pouring a gallon of water on the VP can fix), or the CPS going bad (usually a code). And again, its not uncommon for one of the batteries to be bad and cause all kinds of problems.