So I bought a used airdog off my buddy a couple month ago. It is the older version. Everything works on it but I’ve been noticing that it doesn’t keep pressure constant. I set it to 18psi at idle but if I really get on it it will go down to around 11psi on a really hot tune. Is this a sign of my motor getting weak? I’ve seen some write-ups that you can order a 4g motor from airdog and it will fit on my airdog. Is this drop in psi normal or is it getting weak? Or is their something I can do to keep it at a more constant psi all throughout my throttle position? 

Anytime you’re seeing fuel pressure drops like that, first thing I think of is what size fuel lines you’re running? If you’re 1/2in all around then I’d say double check the regulator (however your pump has it setup). Then I’d double check my gauge to make sure it’s reading correctly. If I had the fuel system open recently I’d leave it be for a bit to let the air work itself out. If all that’s been checked good, then I’d been leaning on the pump possibly being on the way out. 

33 minutes ago, notlimah said:

Anytime you’re seeing fuel pressure drops like that, first thing I think of is what size fuel lines you’re running? If you’re 1/2in all around then I’d say double check the regulator (however your pump has it setup). Then I’d double check my gauge to make sure it’s reading correctly. If I had the fuel system open recently I’d leave it be for a bit to let the air work itself out. If all that’s been checked good, then I’d been leaning on the pump possibly being on the way out. 

It is all 1/2” line from the pump straight to the vp. I bypassed the factory fuel bowl. I did take the spring and ball out and added a spacer to bump my psi up from 16 at idle to 20 and it adventually settled at 18psi after running the truck for a bit. It has a new (2 month old now) quadzilla guage so I don’t think it faulty. More than likely it’s a worn pump then. Guess I’ll have to take the $500 kick in the gut on a new 4g motor sometime ?

Guess it couldn't hurt to double check your return spring to make sure it hasn’t got bunched up using the washer and is causing bigger fluctuations then expected. I’d also check the integrity of the return ball as well. Any sort of noticeable grooves or markings from the spring can cause it to give way more then it should and your fuel pressure will become erratic. I’ve had both scenarios happen to me.

 

I wouldn’t assume your quad gauge would be faulty either, but a 30 dollar mechanical gauge to verify whether those pressure swings are being exaggerated or not via the electronic gauge is much more appealing to me then 5-hundo on a new pump. 

 

Have you thoroughly checked there’s zero leaks on the supply side? Even a tiiiiny one could cause a bigger swing. I assume you're also running 1/2in line on the airdog return line to the tank right? 

 

Just trying to think of everything cheaper than a new pump lol

6 minutes ago, notlimah said:

Guess it couldn't hurt to double check your return spring to make sure it hasn’t got bunched up using the washer and is causing bigger fluctuations then expected. I’d also check the integrity of the return ball as well. Any sort of noticeable grooves or markings from the spring can cause it to give way more then it should and your fuel pressure will become erratic. I’ve had both scenarios happen to me.

I don’t remember it having any grooves but I’ll have to check that once it’s gets somewhat warmer out for me to be able to bare the diesel shower ?

 

I wouldn’t assume your quad gauge would be faulty either, but a 30 dollar mechanical gauge to verify whether those pressure swings are being exaggerated or not via the electronic gauge is much more appealing to me then 5-hundo on a new pump. 

 

Have you thoroughly checked there’s zero leaks on the supply side? Even a tiiiiny one could cause a bigger swing. I assume you're also running 1/2in line on the airdog return line to the tank right? 

Yup, everything’s 1/2”. No leaks that I can tell. Not seeing anything under the truck other than the normal oil leak 

 

Just trying to think of everything cheaper than a new pump lol

 

Hose clamps my friend!

 

I usually take a paper towel and grab anywhere there could be a potential leak with the engine running. That’s a good enough sanity check for me to say no leaks. 

I would say you're still having problem with ball and spring. How are you getting fuel out of fuel tank are you using a draw straw, and are you returning to the filler neck. Do this to your spring, that side would go towards the ball. This will keep the ball from getting stuck inside the spring.

Mine a variation on the same thing I just bent the tail in a 90* towards the inside preventing the ball from sucking in as well. You have to check on it over the years may every other year and you'll find the vibrations will bend your tail down some.