Pressure setting changed a few times when it was new. Now one year old. Noticed pressure getting lower but pressure dropped below 10 towing a heavy load. Fuel filter plugged? Stopped and changed filter. Nope, wasn't plugged. Readjusted pump up to 21psi not running,18psi at idle. Pulling load now at 15 psi. Thought this readjustment thing would end with age.

Have you checked pressure with a test gauge? Your situation is exactly like mine was. Put a test gauge on it and it was 35. Isolator was bad. Plumbed diesel to gauge and all is good!

Have you checked pressure with a test gauge? Your situation is exactly like mine was. Put a test gauge on it and it was 35. Isolator was bad. Plumbed diesel to gauge and all is good!

 

Really common with isolators.

 

As for the change it common to see adjust able Raptors and AirDogs do this where the over complicated valve starts sticking and hanging up so the pressure gets lower and lower. So now you adjust it the pressure is higher and all of sudden it will pop loose and be too high. So I suggest you pull the valve and inspect it for damage.

test fp with a different gauge to verify the drop in pressure.  if another gauge shows the same then get on the phone with airdog and ask for jarren.

The same problem I'm having w my Raptor, my pressure was getting a little lower but dropped down to 11 PSI at idle used to be 16psi, so I figured it was also a dirty filter.After the change, It did help a little, now up to 12psi at idle, a far cry from what it was.

 

I don't really know what the isolator is for sure. Should I just turn it up for now or let it work itself out maybe?

 

Thanks,

Dave

You need a test gauge to definitively diagnose gauge or pump problem.  As I stated before, I had the same issue.  Kept turning up the pressure.  Finally got a test gauge and after multiple turn ups at the pump, actually tested 35 psi.  Kinda like adding a quart of oil each time the oil light comes on without checking the actual level with the dipstick.  Exact same symptoms you're having.  Mechanical Test Gauge from Vulcan Performance.

 

Test gauge should be purchased before any other mods to your truck. You just gotta have one.

Edited June 7, 201410 yr by joecool911

My gauge, is a liquid filled test gauge plumbed to the vp with 1/4 inch polly. The restrictor is a solder filled fitting drilled out .020

Still seems to come back to the regulator of the pump is screwing up. Something about the old school method of check ball and spring worked so much better compared to the current method of adjustable regulator.

This is the 1st time I've ever turned up the pressure. Not even a 1/2 turn in.Even at about 4 years old, my replacement Carter when I 1st bought the truck didn't hang in there for 2 years. I'll just keep an eye on this Raptor.

 

Dave

This is the 1st time I've ever turned up the pressure. Not even a 1/2 turn in.Even at about 4 years old, my replacement Carter when I 1st bought the truck didn't hang in there for 2 years. I'll just keep an eye on this Raptor.

 

Dave

 

I would pull the regulator and inspect it for damage or sticking of the springs.

OK Michael, I'll put it on the list!

 

Thanks,

Dave

I have taken my regulator apart and inspected it. I see no difference from the fixed spring and shim regulator. The pump is located on the frame right below the drivers seat. Handy for readjustment.

Mine in over 4 years it's the only adjustment I've ever made to it, I would think so far so good!

I am having the same trouble with my Raptor pump. It was new in December and it has been adjusted twice so far. Each time I adjusted it to 19psi idle and it gave 15.5 at WOT. Now it has dropped to 15.5 idle and around 11.0 WOT. I also changed the fuel filter thinking my filter was dirty but it made just around 0.5 psi difference is all. Am now back down to having to adjust it again, one more time.

Need to check with the manufacturers to see what they say re warranty.

At least I know it is not just me that is having this problem.

1/4 turn will add 4 to 5 pounds. Don't start cranking it in and blow a gauge like I did way back in the beginning.

1/4 turn will add 4 to 5 pounds. Don't start cranking it in and blow a gauge like I did way back in the beginning.

Good to know on the 1/4 turn = 4-5 psi!

Even better to know with a test gauge exactly what you're setting it out. The one I got from Vulcan has a long enough hose that I can see the gauge while adjusting the raptor. Just make sure your warm so that the full voltage is at an operating level and grid heater is not cycling on and off. Since I removed the isolator and plumbed directly to the gauge, my raptor has been rock solid. I got a snubber and a needle valve to buffer pressured to the cage.

Edited June 18, 201410 yr by joecool911

First, I agree with the suggestions about checking your pressure with a test gauge. I use one to verify pressure readings when they begin to deviate from normal. The two things I've noticed about pressure fluctuations with my Raptor RP-100 are that they are related to fuel level or junk in the fuel line. In reading your posts, I didn't see whether you had disconnected the fuel inlet line from the pump. On mine, there is a small, steel mesh filter in the inlet side of the pump. After about a year of running, my pressures were beginning to drop on WOT. They were fine idling or cruising. I replaced the fuel filter on the side of my engine to no avail. I then pulled the fuel line going into the inlet side of the pump and discovered that the mesh filter was full of small bits of stuff. I cleaned it out and my WOT pressure returned to normal (>10 PSI) with only about 4 PSI drop from cruising pressure. I added a Donaldson filter between the tank and the pump after that and I haven't seen that particular problem since. One other pressure drop I've noticed is when I run the tank down to nrely empty. The pressure readings drop significantly when I'm into the throttle until I get down to town to fuel up. After that, no more issues. Hope these comments help!

A pre lift pump filter helps to keep the regulator and pump in good shape. I looked for the little screen to take it out but my Rapter 100 had none.

Michael, I have an extra Frantz filter setup, would I be able to use it in this case? Between the tank & pump?

Dave