Fuel Pressure Bleeding Off

[Dubbalduce2r4i]

Ok i have beening reading up on a few posts. But haven't found a whole lot. I have a Aeromotive afpr, and Wally. When i shut the engine off the afpr guage drops fast to zero. I did the afpr test by pulling the vac line off and snaping the throttle back 3 times. the pressure didn't drop when throttle was released. I also read a post when Shaeff was having problems with his soup, spiders in the fuel filter. This was posted by Stevevangst, post #38. (there is one way you can check if your fpr is good or not, go get a vac test pump and hook the vac lines up onto your fpr and pump too see if it holds good air, I mean of couse it's going to leak a little due to the design of the top screw that has no kind of seal build into it, but other then that your pressure you pump or suck out of it should not drop too fast)
Well, i bought a vaccum pump kit. Hooked it up to the vacuum line on my afpr, and pressurized it, and it bleed off really fast. I also read that if the diaphragm is torn it will leak gas into the vacuum line. But there was no gas in my vacuum line. Is this a correct way to test the afpr? Or would a bad relief valve in the wally cause this to happen? It is a brand new regulator, it has about 30 miles on it. Any and all input is greatly appreciated. Thanks in advance. Ken

 

[suprahero]

I'll be interested in the answers you receive as well. Mine won't hold pressure either. When I cut my car off, it goes to zero. When I turn my key on, it goes back up to 35psi.

 

[91 mK3]

same here. myne used to go down very slowly. it would hole at about 20, then drop down. now it just drops down to about 3, then 0.i thought it was my fuel cap but i tested it with a known working one and its fine.

 

[Dubbalduce2r4i]

yeah mines drops really fast, They say it is suppose to hold pressure for 5 minutes. Mine drops to zero in a matter of seconds. i have a new gas tank, and all new tank seals, and gas cap. New fuel filter. Only thing i haven't rplaced yet is the rubber fuel lines. I guess that is next on the to do list.

 

[grimreaper]

i called aeromotive tech a few months back, they told me they dont build one that holds rest pressure. Jump the fuel pump at the diag. box and pinch the return line. If you hold the line shut while removing the jumper it will hold the pressure. That way you can at least verify the injectors arent leaking or the relief valve.

JJ mentioned a part you can add after the regulator to allow it to hold pressure, how ever i couldnt find one for less then a few hundred dollars.

the aeromotive is very simple to pull apart to check the diaphragm. 4 little allen head screws and thats it

 

[Dubbalduce2r4i]

Thanks Grim, that is good to know about the regulator. I will give that a try and see what happens. Like you said atleast check to see if the injectors and relief valve are bleeding off. I'll let ya know how it goes. Thanks again

 

[91 mK3]

please keep all of us updated. also, if the pressure is being relived somehwere, wouldnt you be smelling fuel or fuel vapor?

 

[Dubbalduce2r4i]

Ok so i piched closed the fuel return line, place the jumper in Fp & +B, turned the key pressure was at 80. Removed the jumper and pressure dropped to 60 and stoped. After 8 minutes it was down to about 52. Might not have gotten all of the return line pinched as i only have about 4 inches of rubber line before it hits the hardpipe. I am using stainless braided line. If the relief valve was bad, would it bleed off pretty fast? Also if the injestors were leaking, would it bleed off slow? How could you check for injectors leaking, they are brand new Pte 550's, with new seals. Thanks again. Ken

 

[Dubbalduce2r4i]

Gonna have to replace that 4" rubber line and try it again. It was old and i put a hole in it when i crinped it closed. It is leaking/ dripping when i started the car. Plus i need to get rid of the squeeze clamp where it goes to the hard fuel line. So i will try again tomorrow.

 

[grimreaper]

im guessing you didnt get it pinched closed 100%.

 

[CajunKenny]

Isn't 80psi a bit high...? Ok...more than a bit.

 

[Dubbalduce2r4i]

That is what it jumped to when i pinched the return line closed. That is not what i have my fuel pressure set at. Anyways, finally got time to fix the bad rubber return line, and it is now holding pressure with the return line pinched. So my injectors are not leaking, and my relief valve on the Wally is good. Anyone know of a good place to get a tune, preferrably here in Fort Worth, Tx?
Thanks again Grim.

Ken

 

[grimreaper]

You can road tune! Start at 2500 in 4th and do a wot to 3-3500rpms and make adjustments. I do 500 rpm runs until i get a nice af ratio in the midrange and work my way up. Dont pull more then %20 on the safc and knock base timing down to 8 degrees for now. If your pulling 20% or close to it drop the Fuel psi down 2-3lbs and start over with the safc adjustments at 0. You have lots of "roaming" space on the west side of FW. I shoot for 11.0 af ratio to give some room for error when the 110+ degree texas heat comes back

 

[Dubbalduce2r4i]

Thanks for the heads up Grim. Only down fall is my inspection is out. So i am leary of running into some 5/0. I live on the westside, and they are thick over here. Might just have to head out towards Weatherford and give it a shot. Again thanks for all the help, i really appreciate it.

Ken

 

[oldsking]

So just to revive this old thread instead of me starting a new one, its cool for the pressure to drop after the key is turned off? When I open the key and flip the switch to my pump goes to pressure but once I shut the car off, right to zero. Im running SX performance inline pump with 8an feed into a 6an at the rail with 560 injectors and an aeromotive fpr. I did however realize my vacuum line is not doing it;s part for my fpr so pressure stays the same as I rev the engine, not good right?

 

[northwestsupra]

So just to revive this old thread instead of me starting a new one, its cool for the pressure to drop after the key is turned off? When I open the key and flip the switch to my pump goes to pressure but once I shut the car off, right to zero. Im running SX performance inline pump with 8an feed into a 6an at the rail with 560 injectors and an aeromotive fpr. I did however realize my vacuum line is not doing it;s part for my fpr so pressure stays the same as I rev the engine, not good right?

My whole fuel system is brand new and during the testing I dont even recall my new areomotive for holding psi

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[metaphysico]

Once I swapped my walbro into my car it never held pressure figured it was just the pump is not designed to keep pressure. I don't mind it though I never have to worry about bleeding off fuel pressure to work on it.

 

[oldsking]

okay I feel better now haha I was just reading the tsrm and its saying it should hold for 5mins but they doesnt take into consideration modded cars with big pumps and injectors lol thanks guys!
1 other thing, if my vsv is not plugged into my harness will it not help in pulling vacuum to my reg? Currently I have no vacuum from the factory source. I have the vsv hooked up with vacuum hoses but no plug from my harness (it was not there when I got the harness) I am thinking alternate source like the throttle body perhaps?

 

[grimreaper]

my pump holds pressure just fine, its the aeromotvie fpr that doesn't hold pressure. pinch the return line while jumping the fuel pump in the diagnostic box with the key on/motor off. Remove the jumper. Fuel pressure should remain unless its leaking at the injectors, pump, or externally.

 

[89supra7mgte]

Mine does the same thing, With afpr and pump, assumed it was normal because it did the same thing on stock fuel system.