GLH

Kurt,
Thanks for the input.

I can't make the Miami Boat Show my wife is due with our second son on the 15th of Feb... unless you supply me with a way to explain to her I need to be at a boat show while she gives birth!!!

GLH

Dave I have switch the senders around and the gauges around
, also I checked it with suplemental mechanical gauge and it still fluctuates.

GLH

Those were yanked out before I bought the boat last January.

I also have changed the fuel filters and changed pumps again for a minimal difference and then back to the same unreliability in pressures. Also this is only happening on one engine. Although while winterizing this weekend I noticed I have a very small leak on the pump that actually is working and holding pressure fine...

I love boating man!!!

Iggy

Are the pumps mounted as low as possible?
I always thought they should be mounted at or below the bottom of the fuel tank. I say this because electric pumps are not good at pulling the fuel from the tank, but excellent at pushing it up to the carb. That's why EFI pumps are generally mounted in the tank. There are exceptions, but they are frame mounted and below the fuel tank.

robyw1

The Mallory 140 pumps are great AS LONG AS YOU USE A RETURN REGULATOR. You should never deadhead an electric pump if you expect it to last. I have burned up 1 Mallory Comp140 and 2 Holley Red pumps by deadheading. Once I used the return regulator the Mallory lasted indefinitely. Now on the issue of low fuel pressure on the carbureted engine; I don’t see this as being a major problem. Your engines are eating up fuel and your mechanical pumps are doing the job of filling the bowls. If your fuel pressure were high on a mechanical pump carbureted engine then the case could be made that you lacked sufficient fuel flow. When do you have this higher pressure? You have it at idle when the carburetors needle & seat are closed, or you could have it because of an obstruction. If you’re maintaining 3-PSI on a carbureted engine under full throttle then things would seem normal to me.

If you want to use an electric pump then great. Make sure to mount a regulator as close to the carburetor inlet as possible, and make sure you use the return style. This will guarantee you have sufficient fuel flow to your inlet or inlets (Holley) However You will still notice that fuel pressure falls off. Remember just because your fuel pressure is higher DOES NOT necessarily mean you getting more fuel flow to the carburetor.

On EFI engines things are very different. All EFI fuel systems in production today use the return to tank delivery. The benefits of this are the increased pump life, a never-ending supply of cool fuel to the engine (reduced vapor lock) I could go on but will digress. You have to look at the fuel pressure very different on a port EFI engine. Injectors are solely responsible for atomizing fuel and do so in a very fine matter. It takes at least 25-PSI for the modern disc-type fuel injector to properly atomize fuel. When the demand for fuel increases (full throttle) the injector will have to atomize a greater amount of fuel per shot. Two things have to happen for this to take place. The opening duration for the injector (pulse width) has to be extended and the fuel pressure must be increased. This is why you see your fuel pressure jump up when ever you open your throttle. On most EFI systems the fuel pressure regulators are controled by manifold pressure. Under vacuum the fuel pressure is lower, with less or no vacuum the pressure is increased and in turbocharged the regulator is pressurized to further increase fuel pressure.

In my opinion electric fuel pumps are the way to go whether you are carbureted or injected. Mount the pump to where it will be gravity fed because forcing the pump to prime itself can significantly reduce its output.

Sorry for the length but I was bored today

Roby

monsta

Just a suggestion. start with the pick ups. most mechanics do not. for big power applications, it is necessary to have ample diameter. also check for the proper use of fittings, from there back. I have seen #10 lines coupled to, for example a -10male flare to a 1/4 or 3/8 pipe nipple on opposing end, whats the use, restrictive. I.D is very important to maintain through out fuel system. I have also installed secondary fuel system's, which under boost assist the primary system to maintain pressure. Activated by a manual switch, or a boost activated hop switch. The secondary system is tee-ed into the primary on the out side of the mechanical pump. Very important, you must use A 1 WAY VALVE, between the " tee " and the electric fuel pump of the secondary fuel system. Additionally both fuel systems have separate fuel water separator's, and pick ups, and use the same return to the tank.Outside of using a NOISY Weldon electric pump and reg, this system work's best and is very reliable. It is also a fail safe to make sure your getting home if the primary mechanical pump fail's. One last thing , pump's water sep's , must all be mounted as close to pick up height as possible, and never have descending/ ascending height fluctuations. Always ascending. Hope its a help

GLH

This system worked perfectly with the current lines (9lbs on idle and 5.5-6 lbs. WOT) installed for the first 40 hours something is messing with me here. Now one engine goes down to 3.5 lbs between 4100 to 4900 and goes back up to 5lbs passed 4900.

Thanks for the input keep it coming. Here is some more motivation from the home country.

waterheater

Nice Toe

jmackin

iTrader: (1)

GL,
I think Phil L. worked on mine before I bought it and he said it has a sensor and it will shut down if fuel pressure drops. Wont solve your problem but I thought it was a good idea to have. JM

ONESICKGLADIATOR

Hey GL
This pic can keep my fuel pressure from drops

Rick OSG