Makes no sense.

[TROOPER254]

Installed raptor 100 about one month ago fuel pressure changes about every three days and has to be adjusted Up or down 3-4psi is this a problem with the raptor? If the screen on the inlet is clogged would it pump 42oz fuel at the vp in one cycle? When you set fuel pressure at 17psi at idle wot is 13 is that normal? Thanks Ed

[Mopar1973Man]

AirDog / Raptor with the adjustable regulators are known for issues of stability. I would contact Pureflow and find out if there is a updated regulator or if you need to just replace it because of a damage regulator unit.I would like to ask if you have the Big Line Kit all the way to VP44? Is there any Banjo Bolts or stock plumbing left on the truck?Another thing to check for is air leaks at the suction lines. A way to check this is to pressurize the fuel tank by using a blow gun and a rag at the filler neck. Just give it about 1-2 PSI and have a friend crawl around looking for wet spots or wet connections. AirDog / Raptor quick connectors are known to leak air as well.

[TROOPER254]

Checked for leaks could not find any will call ad tomorrow. All fuel lines are stock except from ad outlet to fuel filter.Thanks Ed

[gassernomore]

When I first installed my Raptor, the pressure bounced around like yours. I went back thru all of the connections and tighten them. Been rock solid since. Pressure difference sounds like it is coming from the stock lines.

[oldbeek]

My raptor 100 changes a few pounds every few months. I have learned to live with it. Original set was 18 idle dropped to 14. Reset to 18 then it moved to 21. now back to 18. I run 3/8 lines with 3/8 banjo fittings and 3/8 banjo bolts from Vulcan which is 180% larger than stock.

[Mopar1973Man]

Something about the Raptor/AirDog pumps and the adjustable pressure regulator... I've never had a chance to see or to play with one to see if there is something else that can be done to fix it.

[Deafautotech]

Same with me as with raptor 100 that would do change pressure itself. Every tenth times( it is when I am start to drive not every time when I am try to make it happen at my garage to test it. ) now it would drop from 20psi to 15 psi then I tried to adjust it but it won't make any change. I will néed check the screen and see if possible of regulator issue???

[oldbeek]

Something about the Raptor/AirDog pumps and the adjustable pressure regulator... I've never had a chance to see or to play with one to see if there is something else that can be done to fix it.

Looks like the same as the pumps with the spring and adding a shim behind the spring. Only here you just screw in or out the adjuster 1/4 turn to change 3 or 4 lbs.

[diesel4life]

With the Raptor pumps they are putting out a constant pressure and all your doing by adjusting the regulator is either opening up or closing off the flow of the fuel. I only ran a Raptor for a little over a year before I converted it to an AD100 frame but my pressure was always steady. Make sure your regulator is locked down tightly because vibrations could cause it to loosen up over time. The only other variation I can think of other than a plugged inlet would be the motor varying in rpm. I've had mine apart and I can tell you the brushes are very cheap.A few pics of the Raptor regulator

[dripley]

My ADII has the adjustable regulator. I fiddled with it the first few days after install and have not touched it since. It sits just north of 19. Thats been 2.5 years ago and it has never moved. It appears to be the same as the ones on the Raptors, but thats just comparing photos.

[Ilikeoldfords]

Mine bumps the pressure around just a little bit until I get out on a road trip. Then it'll settle at a steady pressure. The other thing I was thinking about the OP, how is your voltage? If you don't have steady power it will fluctuate the pressure because the pump rpm's will go wherever the voltage goes. You might have a bad connection somewhere. Just a thought.

[Mopar1973Man]

Way different that old school AirDog 150's... The only problem mine had was cramming the check ball back into the coil of the spring which I fixed by egg shaping the last coil. Very stable. But looking at Raptor's adjustable regulator there looks to be way too much stuff to bind up, stick, wear out. Compared to mine its just a plastic ball coated in rubber. Lots of steel on aluminum http://forum.mopar1973man.com/attachment.php?attachmentid=6101

[diesel4life]

The AD100 is the same as the 150. They both have fuel returns and dump excess fuel back to the tank. The Raptor set up simply "blocks" the flow of fuel with the adjustable regulator, no return line to the tank. I have wondered if that could be part of the reliability issues with them because the more you decrease the pressure to the injection pump, the more you are restricting the flow of the pump, essentially dead heading it so to speak. I believe the 100's and the 150's have a little better set up because the pump is always unrestricted, whatever doesn't go to the injection pump gets dumped back to the tank. The pump does not have to work as hard this way.

[Mopar1973Man]

Or is it like the old stock Carters that just return the fuel flow back to the input side? Re-circulating the fuel from output back to input.