Why Would My Fuel Press. Change ?

[Hallett19]

Well, as I let my boat sit in the driveway for about 20 min to idle (yes, I detached the drive shaft to the pump) I noticed my fuel pressure was around 6 1/2+ at first, and as I went to check the motor a second ago, its at a touch over 4. Its a mech pump, edelbrock kick ass pump. As I was adjusting to make more fuel pressure, it couldt get any more than 51/2. I pulled the adjuster screw on the regulator all the way out till it hit about 31/2, then screwed in,the fuel press. needle moves with every turn untill it hits 5/12, and I turn it 3 WHOLE turn in to raise fuel pressure, nothing, wont get anymore .... does this mean my fuel pump is bad ?
[ July 21, 2003, 03:33 PM: Message edited by: Hallett19 ]

[Hallett19]

going once .....

[77charger]

GO ELECTRIC :D :D
Is it self regulating?it might have a max setting at 5.5 psi.(i really dont know mech pumps but a guess at best)

[DEL51]

Hallet, do you have a standard holley regulator? Is it runnng ok at Idle? The first thing I would do is to Check the needle and seat. watch the carb while the engine is running.Make sure the bends to the regulator from the pump make no sharp 90 degree turns.If this is all ok you have to look at the pump and regulator.Is the regulator new or been on there for a few seasons.

[Hallett19]

regulator is new and no crazy turns. The pump would read almost 11psi before I put the regulator on it, and the regulator is adjustable from 3 to 9 psi, but I cant get 5.5 out of it.... It was at 6.5 when the motor was fist started.

[BK]

I have the same thing happening with mine. The Holley regulators are kinda junk from my experiance, this is the second one ive had problems with. My fuel pressure starts out at 7 1/2 then after the motor gets warm I dont see more than 5 1/2 no matter how I adjust it. Mabye its normal for the pressure to drop a little after the motor warms up?

[flat broke]

Aaron,
Try plumbing a gauge between the outlet of the pump and the inlet of the regulator to make sure you are still getting good presure to the regulator. Then if that is the case, it looks like you may want to swap regs and see if you get any improvement. BTW, I have a feeling that 5.5psi at idle is going to equal a lean condition when you're on the throttle.
Good Luck,
Chris

[Blown 472]

IN a word, bypass. I had the same trouble with my set up, that and the fact the holley reg has a very small hole that the fuel goes thru.
A bypass system will give you full volume to your carb/s first and you regulate the out flow not the inlet.

[Mr Twister]

I just sorted out a similar situation on my SW. At WOT the boat would just lay right over, be untuneable lean etc. Here's what I figured out:
1. Holley regulators are junk for a performance application. Open it up and look at the size of the valve seat. Trash it get a good one.
2. The tanks may not be adequately vented, mine weren't. Install a vent.
3. The fuel pickups in the tanks "of the day" were tiny, on my SW it is 5/16 OD tubing shoved in the outlet fitting screwed into the top of the tanks.
4. Deadhead systems make it difficult to properly regulate fuel, switch to a bypass system. Go to the dragstrip and look at the fast cars.
My tanks are at the weld shop getting bungs added, hope my personal opinions help.

[78Southwind]

Has anyone ran the bypass back to the water/gas fillter and had some success? Would there be a problem with this set up?

[VD CRUISER]

I have a Perma Cool filter/separator that has 2 inlets and I plumbed the bypass back to one of the inlets. Seems to work great.

[CARLSON-JET]

Has anyone ran the bypass back to the water/gas fillter and had some success? Would there be a problem with this set up?
78, I run a holley marine blue fuel pump, and the holley reg. .. when I dead headed it the first time I hooked it up there was trouble. After about 30 minutes the pump would overheat and start to slow down then run sparatically and finaly ceased to move fuel. I would shut it down for a few minutes and it was cooled off enough to work again. I read a thread on RJB about installing a bypass. The ones that were diagrammed out looked suffiecient and had worked for those applications. My problem was I was finished spending any more money on the costly braided lines and fittings. I had a 3-AN line left over from a nitrous setup I had that seemed to be about the right size to allow fuel to flow but still add enough restriction for the bypass to be functional. I also in the discovery proccess cut the bypass spring in the holley pump to stop the pump from building up too much pressure before the reg. I run a single carb so one side of the reg. was just blocked off so I used that for the restricted return line. from there I ran it into what would be the air blead on top of the water separator/filter. this has worked for me and keeps the pump cool enough with the volume of fuel the filter all the lines hold... I did have to blead the air out of the system at the carb, but once that was done it has worked very well.

[78Eliminator]

Do you trust your fuel press gauge?

[Hallett19]

damn Justin, you dug this thread up from a while ago. Ironically, I'm still having the problem !! I love my boat. And yesterday I started it up and my eyes started burning really bad and it chokes above 3k rpms. What now !?!?! :mad:

[victorfb]

i had a similar problem and switched to a bypass regulator. no problem now. as mentioned also, how well do you trust your guage? liquid filled guages can and will change with differant temps. most have a small bleed screw that must be adjusted if and when this happens. a dry guage may be in your interest at this point just to be sure. take a hair dryer to your liquid filled guage and see what happens and you will know what im talking about. now imagine the temp changes that accure on were you have the guage mounted. not to say its just the guage as you allready know the air fuel is wrong, but the guage may not be giving you correct readings either. all this said, stupid me still use the liquid filled guage. but i wasnt about to spend 38 bucks on a dry guage when ive got 3 liquid filled guages. and all 3 cost about what 1 dry guage was. what the f8ck?

[roostwear]

Sounds like the check valves are going away. Wave ba-bye, and buy a new one.