fuel pressure dropping over time

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Bewy said:
Your return line might be your issue. It should ALWAYS be as large or larger than the feed line. Stated on p. 2 of the 4309 instruction sheet.
I also use the 4309 reg, bypass mode, with an elec pump. I use a 3/8" feed line, 1/2" return line. Rock steady fuel pressure.
A bypass system is basically a 'full circle' system. Beginning at the tank & ending at the tank. The engine [ via the regulator port ] takes what fuel it needs.
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I think you're *** backward. 1/2" feed line and 3/8" return line. I was using 1/4" return with 1/2 " feed.
 
TT5.9mag said:
That’s a great filter. Expensive but worth it. And they are cleanable. I used two aeromotives very similar. One 100 micron on the inlet side of my electric pump and one 40 micron on the outlet side. That’s what aeromotive suggests. Holley I’m guessing would recommend something similar with an electric pump but with a mechanical pump I’m not sure. The sock in the tank may be enough. Just a 40m on the outlet.
Click to expand...


thanks, that will be my "plan B"

i put in a low ball offer on a similar sized filter on ebay, chinese knock of, im sure, but they took the offer (thats why i deleted that post, didnt think you had seen it yet, and i didnt want to waste your time looking for something i may not use)



so im gonna give that a try
and if it works, great

if not, ill go with the Holley i listed (in 40 M, correct?)


what kind of boat do you run that require such neato filters?
 
You can use a return big enough to drive a bus through and it will not matter, since you're using a return regulator as the return orifice. "Whatever" the size of that orifice is inside the regulator is the restriction. So, running a 1/2" return is total overkill, and probably 1/4" is as well, although that's what most run. It's like exhaust. You can put a 2.5" pipe on a slant six, but unless the manifold outlet is the same, any benefits will be minimal, to non existent. You can listen to the "run the biggest return" guys all you want, but you're wasting your time, since the regulator IS the return orifice. Unless you have a total badass race only car, the biggest return line you will probably ever need is 1/4".
 
diymirage said:
thanks, that will be my "plan B"

i put in a low ball offer on a similar sized filter on ebay, chinese knock of, im sure, but they took the offer (thats why i deleted that post, didnt think you had seen it yet, and i didnt want to waste your time looking for something i may not use)



so im gonna give that a try
and if it works, great

if not, ill go with the Holley i listed (in 40 M, correct?)


what kind of boat do you run that require such neato filters?
Click to expand...
40 micron on the outlet of the pump before the carb should be sufficient.
I have a 21 foot open bow commander jet. Just finished a nasty BBC for it and it will be getting boost next year. I built the fuel system to support 1100hp. I don’t think I’ll need it but I hope to make around 900.
 
TT5.9mag said:
40 micron on the outlet of the pump before the carb should be sufficient.
I have a 21 foot open bow commander jet. Just finished a nasty BBC for it and it will be getting boost next year. I built the fuel system to support 1100hp. I don’t think I’ll need it but I hope to make around 900.
Click to expand...
What fuel pump are you using. inlet ? fuel line ?
 
RustyRatRod said:
You can use a return big enough to drive a bus through and it will not matter, since you're using a return regulator as the return orifice. "Whatever" the size of that orifice is inside the regulator is the restriction. So, running a 1/2" return is total overkill, and probably 1/4" is as well, although that's what most run. It's like exhaust. You can put a 2.5" pipe on a slant six, but unless the manifold outlet is the same, any benefits will be minimal, to non existent. You can listen to the "run the biggest return" guys all you want, but you're wasting your time, since the regulator IS the return orifice. Unless you have a total badass race only car, the biggest return line you will probably ever need is 1/4".
Click to expand...


You can use any size return you want with most pumps. There is at least one Barry Grant pump I know of that uses the return line to control fuel pressure. Too small a return line and the fuel pressure is too high. Too big and you won’t have any fuel pressure.

Other than that, the return line size (in reference to how big it is) doesn’t matter.
 
19CAB164-C118-4101-A937-C3AA67C6CE72.png

I am using an aeromotive a1000 brushless with two 1/2” hardline feeds from two tanks and two 1/2” returns. And an aeromotive regulator.
 
Tooljunkie said:
The vacuum port will increase fuel pressure when you get on it.
And back off it should go back to set pressure.
If it works like efi regulators.
From what you are describing its a delivery issue. Inspect the rubber hoses,connection at tank, perhaps the hose is collapsing.
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was able to go for about an hour ride today and it did it again
started out good, but once everything heated up, pressure dropped
at one point, it dropped to zero, and the car died

so i got out, looked around under the hood, like i knew what i was looking for and spotted this

20210623_175449.jpg



the jumper from the new hard line to the pump has just a little kink in it

not a big deal when all is cold, but when it warms up, the line flexes enough for it to collapse


now i got to decide if i want to try to bend it and get it to shoot straight, or find a different way to keep it from doing this
 
diymirage said:
View attachment 1715755325





was able to go for about an hour ride today and it did it again
started out good, but once everything heated up, pressure dropped
at one point, it dropped to zero, and the car died

so i got out, looked around under the hood, like i knew what i was looking for and spotted this

View attachment 1715755327


the jumper from the new hard line to the pump has just a little kink in it

not a big deal when all is cold, but when it warms up, the line flexes enough for it to collapse


now i got to decide if i want to try to bend it and get it to shoot straight, or find a different way to keep it from doing this
Click to expand...
I would imagine using braided line (like Russell) would be better. Stiffer, and would not kink like that.
 
Leave the rubber line attached and grab hold of the hardline and bend it until the rubber is straight.
 
mountain- mole hill. lol
just bend the fuel line and be done with it.
You should have noticed that when you assembled it.:rolleyes:..
 
diymirage said:
View attachment 1715755325





was able to go for about an hour ride today and it did it again
started out good, but once everything heated up, pressure dropped
at one point, it dropped to zero, and the car died

so i got out, looked around under the hood, like i knew what i was looking for and spotted this

View attachment 1715755327

the jumper from the new hard line to the pump has just a little kink in it

not a big deal when all is cold, but when it warms up, the line flexes enough for it to collapse


now i got to decide if i want to try to bend it and get it to shoot straight, or find a different way to keep it from doing this
Click to expand...

Or make a loop
 
fishmens67 said:
mountain- mole hill. lol
just bend the fuel line and be done with it.
You should have noticed that when you assembled it.:rolleyes:..
Click to expand...

He said it didn't do it until it got hot. So he could have easily missed it.

I agree, bend that bad boy until the hose is straight. Drive it and report back. That's an order.
 
For further notation, rubber hose will kink at a 90 degree angle. :lol:
looks to me you are at 90 degrees.
 
fishmens67 said:
For further notation, rubber hose will kink at a 90 degree angle. :lol:
looks to me you are at 90 degrees.
Click to expand...
That is no where near a 90..I would have noticed a 90 on first assembly
That's maybe 20 degrees?

Either way, it will get dealt with
 
diymirage said:
That is no where near a 90..I would have noticed a 90 on first assembly
That's maybe 20 degrees?

Either way, it will get dealt with
Click to expand...
I dont believe that the hose is "heating up" and kinking. Once a hose kinks it stays kinked they dont cool off and magically straighten out.
Yes get rid of the kink that will help.
Your problem lies elsewhere my educated guess is back at the tank.
Keep looking and Good Luck
 
512Stroker said:
I dont believe that the hose is "heating up" and kinking. Once a hose kinks it stays kinked they dont cool off and magically straighten out.
Yes get rid of the kink that will help.
Your problem lies elsewhere my educated guess is back at the tank.
Keep looking and Good Luck
Click to expand...
Saw this once before on a efi dodge pickup. Fuel filter was replaced and owner put new longer hose on.
 
Tooljunkie said:
Heat and vacuum will do it.
Click to expand...
I agree with ya seeing that it is on the suction side of the pump, Lord knows I have been wrong before.
Once the OP straightens the line we will know.
I still smell an issue elsewhere.
 
512Stroker said:
I agree with ya seeing that it is on the suction side of the pump, Lord knows I have been wrong before.
Once the OP straightens the line we will know.
I still smell an issue elsewhere.
Click to expand...
i am confident i can have more then one issue in the same system at a time

but this is one i KNOW is part of the problem, so i will address this one first
 
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