blown formula

Last summer my fuel pressure was set at 7# static pressure (high pressure Aeroquip axial pump). the gauge was steady & the regulator smoothly raised pressure # for # of boost to a max of 12#. Adjusting was smooth and the needle would follow on the gauge very well. Last weekend, I splashed the boat and the fuel pressure remained at 5-6#and never changed as boost increased. I shut it down fast! I disassembled the regulator looking for rips, tears or trash.....nothing was wrong. reassembled it and turned it on....the mechanical and electrical gauges both are steady up to 6# then start to flucuate rapidly. At least the regulator is responding to adjustments now, unlike before. What is causing this wild pressure gauge fluctuation? Line are stainless AN-8, no restrictions, no water, filter/seperator not clogged, engine starts and runs great......So, whats wrong with this??? Did the regulator spring (replaceable) give up? It feels strong but????

formula233

The pressure gage's sending unit is proably failing. It's like an old stereo's volume control that makes alot of static.

Mr Gadgets

Hey blown,
I would try a mech fuel psi gauge to check the other one.. if your sure it is accurate. I would run the pump and supply an external source for vaccumm and boost. See what he regulator does. You dont need to run the motor to do this.. just supply the vac or boost and watch the psi.. Now if it still does it.. look for a leak on the suction side of the pump... even take a hose from a can to the pump and see it if clears the problem.. A small leak on the suction side will raise hell with the psi.. If you can.. but a short piece of clear tubing in line with the suction side of the pump and look for bubbles in the line..
NOW .. be careful.... this is gas and it is dangerous.. Kids dont do this at home.. all that. Be safe!!
That should locate the problem.. If not then the regulator could be bad.. subsitute to check it.. Then fix it if possible..
But I think you are sucking air in..


Good luck..

Dick

Turbojack

Some time the most stupid thing is the problem. Do you have a fuel cutoff? Could it be partway on & off? Full of gas? I turn my battery & gas off evertime I get home. When you hit the key & nothing happens I remember the battery switch but I do not always remember the fuel cutoff.

blown formula

I do have a mechanical & an electrical gage. they both oscillate!!
I have pressure & flow like crazy as it spray's everywhere if a fitting is loosened. I will this weekend try putting the fuel suction line in a bucket of gas to eliminate the tank & valve.
Regarding the axial flow pump....is there a rubber/plastic or aluminum impellor in it? Is it possible, there could be a "vane" missing, thereby causing the pulsing??
Thanks for the help guys, I had not even thought of the possible "air" trouble.....(the AN- fittings are all tight tho' as I checked them).

blown formula

Ok, still have the fluctuating pressures.
The mechanical gauge oscillates so fast you can HEAR it!
Variation is small, about 1-2#, & varies above & below the set pressure of the regulator. No air is entering the system & I hear a slight hammering sound when the pump is on. ?????
Is it possible the Aeromotive pump has a bad impellor??

Mr Gadgets

blown formula,

It sounds like the regulator is not opening and closing smoothly. I was thinking it may be boost referenced, that is why I mentioned the vac/psi trick to fool the regulator when the motor isnt running.
You say the osc is a 1-2#.. is that with the motor running? What do you get if you just turn on the pump and let it sit without the motor running? You could also romove the line going to the carb(s) and put valve in line.. shut the valve and see if that gives you correct psi ... then open the valve simulating fuel flow. Does the osc come back??
I dont know what the construction of those pumps are. You could call Aeromotive and ask for tech help.. They may be able to shed some light on it.. I would eliminate all the possibilities and narrow it down to the pump or regulator.. You subsituted the tank, now sub the motor with a valve and if it still happens.. it has to be the pump or regulator.
It seems the only way now is to subistute till you find out what is happening..

Good luck

Dick

blown formula

Dick,
I would do the substitution thing, but another regulator is over $100.00 & the pump is more than double that!
The fluctuation NEVER goes away, engine running or not, pressure/boost hose on or off, plugged or not. I do not have a pressure pump gun, maybe I can set the old air hose regulator to 3-5# and try that on the regulator boost sensor? I even called Pro-charger about this & they had no answer. They have seen the same problem before but don't know the fix. They offered to sell me a new regulator tho'!!
Do you have a good tel# for Aeromotive? If so I will call them. Also Holley.....for the regulator.
Thanks,
george

blown formula

I finally got to talk to someone at Mr. Gasket (Mallory tech line)
775-882-6600, his first thought was the fuel pump was unable to supply the required pressure. No way..... I can adjust the pressure higher than where the pulsing starts. After a long discussion, he advised rebuiding the regulator (Mallory #4309/kit#3156). This is a 3 port + return & supply. I have the kit on order & will do it this friday. Hope it works.

AGGRAVATION28

I had a simular problem a few years on a boat...drove me nuts replacing good parts and wasting money. Finally I removed the check valve from my fuel system....yea, I know the Coasties don't like you doing that....but...the problem went away. You might check to see if ya have one anywhere in your system and remove it. Just a thought..............