Fuel Pressure Problem, Help Please!!
 

Hello all I have a 454/330 with minor bolt on parts that is losing fuel pressure above 3300 RPM. I have a holley RED pump with a Fram high flow water seperator/filter. It is wired with the Painless wiring fuel pump relay kit. At idle I have 5.5 PSI. Getting up on plane and til about 3300rpm I have 5.0 psi. When I throttle up past this, pressure drops to 4 - 4.5 psi. Full throttle is at 4600 RPM at 4.0 psi then after a minute or two drops to zero so I back off and pressure comes back up. All fuel line is new 3/8 I.D and the pump is one season old. This is the first season with the fuel pressure guage so I could see what was going on . Is this pump too small?? Could this be affecting my full throttle rpm as the boat is a 24' BAJA with a 19 degree pitch prop which should be over revving the motor if anything. thanks in advance for any help!!

check the fuel pick up in the tank for blockage. change the fuel / water seperator. why are you not running the stock fuel pump?

J240 , first off you need to toss that fuel pump. They are total junk. The problem your having is when the secondary's open up the pump can't keep up with flow rate, that's why your presure drops.:) Hope this helps.

J240, I carry a red pump as a spare. I normally run the Holley blue pump on a blown 509, two 750's. When I was having problems keeping the blue or black pumps alive, the red pump always got me home. But it only idles at 4-5 pounds pressure and any extended happy throttle nonsense you'd see the pressure going down and have to back out of it. I run -8 line from the tanks (cat with tank in each sponson) to IMCO valve. Then to a big water/fuel filter, to the pump, then to a y-block where it goes to 2 -6 lines to feed each carb. I also run the Painless fuel pump relay. The relay solved my pump problems as well! I think you might have soemthing going on causing a restriction. That pump should keep about 4 pounds on your motor at that rpm. You might check the bypass valve in the pump body, anything small can hang one open a little and not get you full flow to the carb. Most of the Holley pumps though have a small brass screen at the inlet. Check to make sure nothings clogging that as well.

Craig

Chances are you have a check valve at the tank where your fuel line connects to. I think Coast Guard requires builder to install this valve but it restricts the flow.

Guys Thanks for the responces! I"m running the electric pump because the motor is a genV with no boss for the mechcanical fuel pump. I've change the water seperator and also the anti_ sipon valve is removed. The pump screen looks clean and flows fine it will run all day long at 5.0 psi under 3300 rpm.
Baja27 I'm leaning toward your theory that the pump can not keep up with the fuel demand. I sent HOLLEY tech a e_mail describing the problem to them to see what their thoughts are.
So I'll wait and see, I know those pump do not like to suck up out of the tank. Thanks again ,keep any ideas coming and I"ll let you know what HOLLEY says.

Back from a weekend of wrenching and testing. I spoke to holley they suggested the Holley Black pump with regulator. I installed the black pump and regulator and now have 7.0 PSI at idle and 6.5 at WOT 4600RPM. Went out for the first run 10 minutes into it fuel pressure drops to zero, throttle back and pressure did not come up shut down pump felt hot , waited a minute statred back up pressure up to normal. Drove around under 3500rpm pressure stayed up boat ran great. Went offshore for about 45min- 1 hour no problems. Came back in the bay throttled up and i could make the pressure drop if i went over 3800rpm then pulled back to 3500rpm and pressure would rise to normal ?? It seems to happend for no reason and under different conditions. Another time I went WOT and pressure stayed up and it ran great I could not make it drop at all no matter how much I stayed into it. So I went home and pulled the pickup tube it was very clean. Now I have no idea or what to do any suggestion would be well appreciated . This is very frustrating!!!

Any chance you have something in the tank that is blocking the pick up sometimes???

Could it be a cracked suction line???

The electric pumps are cooled by the fuel that runs through them. Sounds like it got hot because it wasn't able to get any fuel through it. I would lean toward a problem with the tank pick up.
Have you had a FULL tank of fuel when you've been losing pressure?? or maybe just a half tank or less?? I would test with a FULL tank and see how the pressure is then. If it stays steady then its something to with the tank or pick up. If not its probably an obstruction somewhere prior to the pump. Who knows, maybe you've got something rolling around in your tank.

Well I agree with you guys that it is some thing with the pick up itself. I took it out sunday and it was clean. I spoke to someone today who told me he had the same problem with his chris craft and went through replacing the same stuff I did to no avail. Turned out in the end, the pick up had a hairline crack in it. So now I'll hunt around for a pick up and try it again on the weekend. Any one know where I can get a pick up for 1988 baja
Think the dealer still has these? Thanks for the input guys as this has been a real downer . Just when you think you fixed it ,there it comes back again.

In my discussions with Aeromotive about a similar issue, the pump may actually be boiling the fuel causing it (the pump) to actually "cavitate" just like a prop can. Is there a return fuel line to the tank from the regulator? Does it feed to the tank or is it "T'd" into the fuel inlet side....it can go either way, but the tank will cool the fuel more. What size line is being used??? The air leak problem (crack in line) could cause the cavitation thing resulting in lower pressure. Any obstruction to the inlet line that reduces flow into the pump will cause cavitation and loss of pressure....... I am chasing a similar problem also and this is what the "experts" say.

Fuel tank pickup ,suck,blow[I hate to say that]will it hold pressure?Fuel lines?[change them]Fuel tank vent?

From the tank to the carb is all new 3/8 " line. Only about 8" from top of tank to pump then to regulator next thru fram high flow filter/water seperator then to carb. No return line in system, the fuel vent line is clear. I no of no other obstructions in the line, it comes out of the top of the tank at a 90 degree then straight to the pump with one other 90 degree exiting the pump.Other then that it is all straight runs . Pump is mounted low near the stringer in front of the motor . I called baja dealer today they said I have to know the manufacturer of the tank before they can even begin to find a pick up " some help they are "! I did notice that the tank has a second pick that is capped right next to the one being used I may uncapp it ,pull it out and switch to the second one and see if this changes any thing. I thought at first it was just plain vapor lock so I moved the pump from where is was to the front and the lines are not near any heatr source like they were before but even with those changes still happends. The pump is hot to the touch but never gets any hotter as we keep checking it thoughtout the day.

Tested the fuel pick up today and it holds pressure fine no leaks.
Removed the fuel gauage sender and looked into the tank appears clean with nothing floating around. I ran a magnet down in the tank to see if it picked up anything but nothing. I called Holley Tech line again and the stated that these pumps are gravity feed pumps and do not suck fuel well at all. My pump is even with the tank outlet but according to holley this is still to high and the pump is not able to maintain pressure. Do all you guys have the pumps mounted below the pick up? if so where are they? Thanks again, the saga continues.. Some day I will be able to actually enjoy driving the boat I hope!!!

are you sure your vent is clear? try running the boat with the fuel cap off once to see what happens

I have always loosend the fuel cap when it starts to drop to see if it made a difference and it never did. When refueling the vent always is clear and vents fine from what I can tell. I think I'm gong to try and move the pump as low as possible to try and get a better feed from the tank.

only ran into that situation once on an older boat....the top 90 degree fitting sould unscrew off the top of your pick up exposing the top of the tube,theres a screen in there that usually causes this exact problem(it has to be an aluminum pick up though),and also make sure your hoses arent deteriorating from the inside,seen them accually tear inside and make there own little flapper inside causing the pump to loose prime........oh ya guys...duh......make sure your pump is located as low in the boat as possible,prefferable below the height of the tank so it can gravity feed itself....these are pressure pumps,not suction pumps....good luck

What kind of a carb do you have? Quadrajet? If so, then there is a filter in the carb. It's right at the point where the line enters. When you take it apart, take note of the spring and be sure to put it back correctly.

You could rig the pump to feed from a 5 gallon outboard gas container or gas can. Make sure the fitting is large enough and secure the can for obvious reasons - be careful.

This would allow you to test against the gravity feed concern.

Have you verified the pressure readings with a mechanical gauge mounted on the fuel line?

I am not that familiar with regulators, but I have not heard anyone mention that yet???

Good Luck,

Steve

The fuel pick up screen was clear but there is only one at the bottom not at the top on mine. IF you hold it up to the light you can see cleaR all the way to the 90 degree. It does haVe a Q-jet which i just replace the filter with a new one in the beginning of the season. I have a mechcanical fuel pressure gauage that is installed and run up to the dash which is what all readingS were taken on. I do know for a fact that the pump is NOT lower then the fuel pick up, I don't know if I can get it lower but I'm sure as hell going to try ., and it think this is where the problem lies . stevel good idea on the aux 5 gallon tank I might try this first. thanks guys for all the advice sooner or later I'M do to figure it out and I'll keep you posted

I agree with the guy who suggested you run from a portable fuel source to see if the problem is in the tank/pickup. I had a similar problem a few years ago. The tank had an ani-reverse valve where the fitting went on top of the pickup which was malfunctioning. I replaced it with a plain angle and the problem went away.