Fuel PSI problem

[wet77]

I had 7 psi first time out and tested on trailer but now it acts like I have air in the system??
OK 2 saddle tanks equal length hose to a filter/seperator one line out to pump then regulator then carb, gauge on carb.
If I unhook the line to the carb and run the pump it prime then works fine as soon as you turn it off you can here the gas run back to the tanks??
if I then hook it back up and run the pump I get 2-4 seconds of 7 psi then 3.5!!
All hoses are braided AN Earls fittings.
Basically pump will freeflow without resistance but when its hooked up to a line with fuel and nothing leaving the carb it can not hold its own and drains back to the tank.
Pump is a holley black.
All this worked fine on the 4th now there is problems!!
I am going right now to fill the tanks to see if it matters if I have them full or not.
I was thinking there must be tubes in the tanks and if there is a hole half way up or something that would cause the pump to suck up fuel then when psi is made it starts sucking air untill the air goes up the lines and kills the psi on the pump :220v:
ANY IDEAS??

[wet77]

Full fuel tanks still same problem??
IDEAS?? :lightsabe

[Boatcop]

How is the tank venting?
If the vent hoses are kinked, or no vents at all, the pump will pull a vacuum in the tanks. That would cause vapor lock in the lines and draw the fuel back into the tanks when shut off.
Try the same thing with the fuel tank caps off, or crack the tank cap when it's running to see if there's vacuum in the tanks.

[Heatseeker]

Where is your pump mounted? The lower in the boat the better. A Holley Black pushes better than it pulls.

[wet77]

I believe it has a relief in the cap but I just tried it,
Both caps open same result :(
Strange thing is I have no fuel leakage anywhere??
But like I said before if you unhook the line right after the regulator the pump in about 2-3 seconds kicks in and has full psi and lots of flow.
Put on the hose to carb (with fuel in bowls) and psi stays at 7psi for a short while then goes back to 3.5, also pulsates high low high low ect....
Is there anything that could go wrong with the fuel filter?? :(

[Oldsquirt]

Doesn't that pump have an adjustable pressure relief valve built into the base? Perhaps that is where the malfunction is.
You might also want to move your pressure gauge to the pump side of the regulator to see what is going on on that side.

[Old Guy]

You don't mention if you have a bypass type regulator or not. I had a similar problem until I went to a bypassing type pressure regulator. The bypass just goes around to a tee in the line ahead of the pump. It works really good (7 psi solid). The rest of my setup is the same as yours (2 tanks w/equal length lines feeding a single 1/2" line to pump).
http://files.triton.net/old1/fuel_system.jpg
Just a thought

[FASTRAT]

it sounds to me that u have the fuel filter in the wrong place?...look at "old guy's" pic & see where he has his filter!...i have the same set-up as urs...but i have the filter in the line coming from the pump to the carbs...n/p & no reg...just my .02 cents
fastrat

[wet77]

Its a holley regulator, one in and two outs
Tanks are not vented and no return line
Thing is it worked fine the first time it was hooked up
Turn on ignition and fuel pump comes on and guage read 7psi
Now its 3-4 and if you let it run for 10-20 seconds it starts bouncing 3-7psi :notam:

[FASTRAT]

Its a holley regulator, one in and two outs
Tanks are not vented and no return line
Thing is it worked fine the first time it was hooked up
Turn on ignition and fuel pump comes on and guage read 7psi
Now its 3-4 and if you let it run for 10-20 seconds it starts bouncing 3-7psi :notam:
ur fuel tanks are vented in some way, shape or form!...my suggestion is...take the reg out & see what happens...if that doesnt solve it...take the fuel filter out & see what happens...this way u should be able to isolate the prob...as i stated in my earlier post...i think u have the fuel filter in the wrong place & its slowing down or clogging up the flow of fuel from the tanks...u have nothing to lose, except a little time, by trying this
fastrat

[Huffer]

Just Went Through The Same Problem,ran Manual Pump For Years
Then Done The Same Thing As You.put On Red Then No Problems For
A Couple Of Months.then Started Again,put On Blue Fixed Again For About Two Months Started Again Put Manual Carter Haven't Had Anymore Problems Since.know What You Mean!

[wet77]

Just Went Through The Same Problem,ran Manual Pump For Years
Then Done The Same Thing As You.put On Red Then No Problems For
A Couple Of Months.then Started Again,put On Blue Fixed Again For About Two Months Started Again Put Manual Carter Haven't Had Anymore Problems Since.know What You Mean!
Was at Iola car show today and a Holley dealer said he has seen there pumps fail within a weeks time :skull:
going to try working on it today more
WANT BOAT IN WATER :mad:
Pump flows like mad when the line to the carb is off at the regulator but as soon as there is no demand for more fuel it will not hold that psi.
I'll try some more ideas and check back in a few hours :cool:

[Old Guy]

If the pump is busy pumping, and the fuel has nowhere to go, the pump will heat the fuel it is trying to pump. This can easily cause the fuel in the pump to vaporize. Now the pump has to pump vapor. It's designed to pump liquid, so it doesn't work very well. A pump used this way can self destruct as a result of the heat build-up. When the pump is pumping liquid, the heat generated by the pump is carried away by the liquid it's pumping.
You say your regulator has one in and two outs. Why does it have 2 outs? Is one of those outs supposed to discharge excessive flow back to the tank?

[wet77]

If the pump is busy pumping, and the fuel has nowhere to go, the pump will heat the fuel it is trying to pump. This can easily cause the fuel in the pump to vaporize. Now the pump has to pump vapor. It's designed to pump liquid, so it doesn't work very well. A pump used this way can self destruct as a result of the heat build-up. When the pump is pumping liquid, the heat generated by the pump is carried away by the liquid it's pumping.
You say your regulator has one in and two outs. Why does it have 2 outs? Is one of those outs supposed to discharge excessive flow back to the tank?
extra out fo dual carbs :)

[wet77]

Ok after lots of trouble and trying different things I hooked the pump up to one tank of fuel. (NO REGULATOR---NO FILTER)
Tank into fuel line then to pump then to carb 3psi and getting worse each time.
I feel its the pump dying :cry:
Used it about 2 hours :yuk:
I am going to order a Mallory pump and try a different one.
My last holley was a blue and I should have learned my lesson from that awefull thing that worked some of the time only.
Also a friend of mine was using a holley blue on his eliminator and fried his pistons because of fuel pressure loss.
I have $15,000 in this motor and can not afford to take that kind of risk.
I am going to try the mallory pn#MAA-4140M from summit
I guess if the pump is not the problem I am wasting money but I hope it will work, :220v:
Are my thoughts right that sucking from a can of gas pump only and into the carb I should see max psi from pump of 14psi?????
It also is much noisier than my holley blue pump that was on my last boat??