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Strange AirDog pressures?


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Ok Gang...While I was out on my camping trip and hauling around my 31' Jayco Eagle Travel Trailer I had some weird fuel pressure problems occuring. Start up cold and get 17.5 just about 18 PSI at a idle and then pull the grade up to New Meadows, ID still holding 16 PSI which is normal and fine. But now as the day got hotter and we got down around Council, ID the pressure fell off to 12.5 at WOT and idled at 15 PSI. Hua??? :shrug: While I was stopped the at one place I played with bumping the starter and you can see 17-18 PSI and then hear a change in pump pitch and the pressure fall again to 15 PSI. It's like the check ball is hanging up again. So I'm going to pull it back apart and double check again. So later on down the road I pick up fuel I figured I add a extra few ounce of 2 cycle oil than typical. Well the pressure went right back up to normal 17-18 PSI at idle and remain normal the rest of the day with no problems.(Enjoying our camping)Now hitched back up early morning and started my way back out of Lowman, ID and got good strong fuel pressure. But by the time I got to Banks, ID the fuel pressure was starting a to fall again. :doh: It went back down to the 12-15 PSI range again. On a few other stops I play again with bumping the start and sure enough yo can see 17 PSI for a burst of a second or two and then falls with change of pitch of the pump. I wondering if the fuel temperature is effecting the check ball and spring some how that its not working properly? Because with cold fuel its working fine but as a soon as the fuel warms up it sinks in pressure? :shrug:Yes... I got a fresh set of donaldson filters on my truck and no change with that...

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Do you have a suction filter installed?

Yes... There is a water seperator and 100 micron prefilter... New filter was installed less than 1,000 miles ago.

Mike, I would lean more toward the ball check valve bypassing too much fuel. Perhaps the ball is binding inside the spring? I have had fuel temps between 120 and 130 and fuel pressure does not suffer with my airdog setup. GB

That's my thought I think either the spring is allow the check ball to squeeze down in the coils again... Or the spring is simply getting tired...
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Here we go... My AirDog Removed and laying on the workbench.post-2-138698180159_thumb.jpgHere is the standard check ball and spring setup.post-2-138698180167_thumb.jpgHere is my setup with 2 shiming washers to increase pressure.post-2-138698180172_thumb.jpgHere is one washer laying on top of the fitting.post-2-138698180177_thumb.jpgHere is the washer slid a little to show it.post-2-138698180184_thumb.jpgHere is how I install the fitting and washers to keep them lined up.post-2-138698180192_thumb.jpgWith a little time and clean up... I'm back to 20 PSI idle and 18 PSI WOT...post-2-138698180199_thumb.jpgTo this day I don't know what causes this check ball to misaligned with the spring or jaming the check ball down into the coils of the spring but I know if I take the time and remove the check ball and blow the port out with compressed air it will work for many more months till one day the pressure falls off and a filter check doesn't fix it...

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Good info thread. But I have to say that my fuel pressure does vary depending on the ambient temperature. The hotter it is outside, the lower my idle pressure is. Down as much as 1.5 psi from 19.5 to 18. My WOT pressure seems to stay at no less than 16 though. I completely dislike driving my truck in triple summer digits given how hot everything gets under the hood but when I do, this happens. Doesn't matter if I run 2-stroke lube or not.Question too..... Is the hole in your shims the same diameter as the hole in the JIC fitting? The shim looks smaller.

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Just slightly smaller on the ID of the washers... Not much...

Are they a chance that the washers are moving or sliding around, even slightly i would think it would play around with the fuel psi. then when you cut engine off it relives the pressure on the spring and allows them to re align themselfs some way:shrug: Richie
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Do you ever run bio diesel? As weird as it sounds, I've heard that bio can cause some kind of algae to grow in the fuel system. And since you consistently run 2-stroke, was there a build up of something related to using that stuff which could possibly get in and around or coat the pressure ball and compromise its sealing ability.

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Nothing on the check ball... I was stuck to the spring again and it fell off before I could get a picture of it wedge on spring. So I took a pair of pilars and slightly bent the last coil on each end in a oval shape just every so slight to hopefully stop this from happening.

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Thats a good idea on bending the last coil. I have been needing to do this on mine for a while now. I am running 15 at idle and 14.50 hwy speed. Does the samething when I just turn on the key 16.50 -17. 17.50 is what it ran when new. I still have my old washer set up from my AD 100, I was thinking of putting it back in. But I belive your right on with bending the spring.

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Hey guys, this may be dumb but I gotta ask. I have an Airdog 2/165. The spring you just pulled out of yours there.... Does mine have one? I'm assuming it's on yur return line to the tank?? Does mine not have it cause it's adjustable pressure? I've battled fuel pressure issues forever even having the pump swapped, changing relief valves on the 44 3 times, redoing all fittings, changing gauges and finally I just gave up for awhile and have been living with pressures all over. Nothing under 10 though. I just recently got the 0216 code , yes I know, but it's been going on since I bought the dang truck. Any helps appreciated. Oh, it's sumped so no straw issues. Thanks....

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  • 1 year later...

Here we go... My AirDog Removed and laying on the workbench. [ATTACH=CONFIG]3127[/ATTACH] Here is the standard check ball and spring setup. [ATTACH=CONFIG]3128[/ATTACH] Here is my setup with 2 shiming washers to increase pressure. [ATTACH=CONFIG]3129[/ATTACH] Here is one washer laying on top of the fitting. [ATTACH=CONFIG]3130[/ATTACH] Here is the washer slid a little to show it. [ATTACH=CONFIG]3131[/ATTACH] Here is how I install the fitting and washers to keep them lined up. [ATTACH=CONFIG]3132[/ATTACH] With a little time and clean up... I'm back to 20 PSI idle and 18 PSI WOT... [ATTACH=CONFIG]3133[/ATTACH] To this day I don't know what causes this check ball to misaligned with the spring or jaming the check ball down into the coils of the spring but I know if I take the time and remove the check ball and blow the port out with compressed air it will work for many more months till one day the pressure falls off and a filter check doesn't fix it...

i'm having some kind of problem too i think. seems that everyones pressure with new 150 air dog about 18-20 mine idels at 14-15 wot 10-12 and just driving anywhere between 13-17 , also tried wix fuel filter instead of ad but it's like 5 microns or somthing and my pressure went up 2psi but i didn't want to leave it on there too long so i'm back to 2 microns. and when it gets cold i luse 2 psi or so . should i shim my spring ? and how many people do that ? it makes sience to restrick return so it build more pressure. Thanks for any help.
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i have a stupid question, how much pressure can air dog 150 put out if lets say i plugged check ball hole off, and how long would it last that way, if fuel could still be returned through pressure line so it doesn't burn out pumping against a brick wall "figurative spich" . i don't know where i'm going with this but i guess maybe thinking by increasing pressure on AD will it not last as long ?

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