Regulate fuel pressure to 15 psi before the injection pump

[WMann]

I read in another post that said there is a pressure valve set to open a 14 psi on the injection pump and when opened it returns the excess fuel to the fuel tank. It is this excess fuel that is flowing through the pump that cools and lubricates the injection pump.

The realiability issues with the lift pump and its sometimes (often times) inability to maintain 14 psi or better fuel pressure, according to the numbers I have seen alot of people posting, I would say that there has to be a better, more reliable system to employ in its place that would make life alot easier on the injection pump.

Question. Is there any reason why you would not want the valve on the injection pump open all the time allowing excess fuel to constantly circulate, lubricating and cooling the pump?

If having the valve open all the time would be a good thing, this is what I think would work.

Scrap the lift pump. Find and mount a more reliable pump near the fuel tank, that is capable of sustaining lets say 20 psi at WOT. Mount a high quality fuel pressure regulator set at 15 or 16 psi between the injection pump and the fuel filter. I would want the regulator between the two so it would maintain a constant pressure to the injection pump and the pump pressure would not be influenced by a dirty fuel filter. the fuel pump at 20 psi would keep fuel flowing through the filter at a high enough pressure that the regulator can still regulate the pressure to the inj pump.

I think a fuel pressure guage between the pressure regulator and the fuel filter would give you two vital bits of information. Working condition of the fuel pump and weather or not the fuel filter is getting dirty and in need of changing. Mabe a fuel pressure sending unit on each side of the filter with a switch and one guage would be a better idea.

I hope some of the resident experts will jump in here and tell us all if this is a working possibility.

Also, someone may have already thought of this and or is already using this or a similar system. I did not find anything in my searches.

Thanks in advance

Wayne

 

[Kent Kuykendall]

Wayne,

I too would like to devise a way to eliminate the posobility of damage to the inj. pump due to a falty lift pump. Who knows, I may have had some damage accure recently when my lift pump went. There is no way of telling how long that it has been supplying a marginal amount of fuel.

Kent

 

[Ron Duncan]

Three pumps:
1. Lift pump
2. Gear pump on "high pressure" injector pump shaft
3. Injector pump

The lift pump lifts fuel to the injector pump unit. This unit has a built in gear pump to supply the injector pump. The injector pump takes what is needed and the excess cools the unit and goes back to the tank through a 14# relief valve.

 

[Vaughn MacKenzie]

I thought fuel was always bypassed through the injection pump so long as there is more fuel getting to it than needed.

With HVAC's system running the Holley lift pump he was steady at 10psi at his injection pump which fluctuated no more than 1 psi no matter if he was idling or accelerating wildly to 120mph. I think he did have a regulator of some type. Somehow I recall in his fuel system research, 10-12psi was best for the injection pump.

Vaughn

 

[Evan A. Beck]

How about a Prime-Loc? #ad

 

[Whitmore]

,fellers,I did this on an 86 fraud and it still works fine, I lost a pump in the tank so its ok I will just use the other tank,well it to soon gave up,I found out the price of 2 new pumps was enough to put my kids thru college so I bought an inline 12v pump and a regulator,I mounted the pump on the frame lower than the tanks,believe it or not the fuel actually flowed thru the pumps in the tanks ok,the fuel pumped up to the motor just fine and the residule went back to the tank via the return line,So I am in agreement that yes I think we are on to a better set up, #ad
Kevin 2001 2500 eth dee

 

[Dane]

Wayne, I suggested the same thing a while back but have not tried it. I think HVAC is running a setup similar to what you described, possibly without the pressure regulator. I think just adding a helper pump near the tank might work as then the 14psi bypass valve on the injection pump would open and take care of regulating excess pressure which would also provide extra cooling and lubrication providing the bypass can handle the volume comming from the helper pump.

------------------
2001 HO 6 speed Regular Cab SLT 4x4 3. 54 anti spin 2500. Used for the daily grind and sneaking away to some secret Baja beaches toting a cabover

 

[Ron Duncan]

Once the engine is reving you probably don't even need a lift pump as the gear pump in the injector pump unit will suck more than is needed (the excess, which cools the unit, is spit back to the tank through a 14# relief valve). The lift pump is only important at low rpms, when the gear pump is at it's worse. Of course if you are totally bombed and run flat out often the more pressure the better/safer.

 

[TowPro]

Dodge is replacing my lift pump because it goes to 0psi at high RMP's, even though its 10 psi at idle and cruse. So I guess this is not true about not needing a lift pump at high RPM.

Originally posted by Ron Duncan:
Once the engine is reving you probably don't even need a lift pump as the gear pump in the injector pump unit will suck more than is needed

 

[Ron Duncan]

TowPro,
You got me on that one! I got a little carried away. I'm sure the lift pump is always needed.
You have a good dealer. Lots of guys have tried to get there pump replaced 'cause they didn't have 10# pressure when running. The manual doesn't address the pressure, except at idle. Mostly the dealers couldn't figure out why these guys were putting these gauges on when they had no apparent problems.
I'm sure there is an old thread some where, where we talked about the pressure readings between the two pumps.
If one pump is supplying 10# pressure into a minifold and another bigger pump is sucking out of that manifold, what would the manifold pressure be?
Happy Trails
Ron

 

[Booster]

From what I have read in DC literature on the fuel system, you don't want much more than 14 psi going to the injection pump (unregulated) - too much pressure apparently causes hard starting, etc...