Fuel Pump Delete...

[jnicho]

The previous owner added an electric fuel pump to my truck.  It seems to work well this way so I think I'll leave it.  However, the old mechanical pump is still on the block and is leaking some oil around it.  I would like to remove the old pump and put some type of plate over the opening on the block.  Anybody every done such a thing?  I would assume it is a simple as custom fabricating a plate and a gasket using the old pump as a template.

[Plymouthy Adams]

you are correct...with the only exception being if the pump also of the vacuum booster type and with that you will be loosing another source for proper level of vacuum under load...acceleration or pulling long grades

Edited December 18, 2013 by Plymouthy Adams

[jnicho]

you are correct...with the only exception being if the pump also of the vacuum booster type and with that you will be loosing another source for proper level of vacuum under load...acceleration or pulling long grades

 

I'll have to look at it again.  I believe there is only a place for fuel line in/out...does the vacuum booster type have some sort of additional fitting on it for vacuum?  How else might one tell if the pump is of the vacuum booster variety.

[Jeff Balazs]

Yes I did exactly that on my truck. A simple plate and gasket is all it should require.

I don't think any of the lighter trucks would have had the vacuum boost feature unless they were modified for some special purpose..

Jeff

[jnicho]

Cool...sounds good.  Would there be any reason to go back to the mechanical pump...other than "authenticity"?  I would assume the electric provides as good or better performance and better reliability.

[JBNeal]

Some folks use both, with the electric as a booster to get the truck started that shuts off when an oil pressure switch closes (or opens, depending on the circuit), then as an emergency backup if the mechanical pump fails.  My only problem with the electric pumps is not knowing when they shut off during operation, as the mechanical pump goes into bypass mode when the carb needle valve closes...haven't done enough research into it to find out if the electric pump would also go into bypass mode or if it would flood the carb chamber.

[Don Coatney]

I don't believe there is a by-pass mode on the mechanical pump. It simply quits pumping when the carburetor float is satisfied and the system pressure exceeds the pump output pressure. I believe the electric pump shuts off when the float is satisfied due to a pressure switch.

[jnicho]

I don't know how it works myself...but I can tell you I've never had an issue with the electric setup on this truck flooding.  Truck always starts very easily with this setup.

[ggdad1951]

I don't believe there is a by-pass mode on the mechanical pump. It simply quits pumping when the carburetor float is satisfied and the system pressure exceeds the pump output pressure. I believe the electric pump shuts off when the float is satisfied due to a pressure switch.

 

it's all pressure to a pump...

[JBNeal]

If the mechanical or electric pump generated flow that was in excess of the carb needs, how does the electric pump know when to stop producing flow?  The mechanical fuel pumps I've played with have two check valves:  one upstream to keep flow from feeding back into the fuel tank, and one downstream to keep fuel from the carb to flow back into the pump.  When the carb needle valve closes, eventually the downstream check valve closes.  But if the engine is still turning the cam to operate that pump arm, then the pump is drawing a suction on something.  Bypass is the wrong term I reckon as flow is not going in some alternate circuit at this point.  So the upstream check valve closes with the pump in operation causing the downstream check valve to close, which brings pump flow to 0.

 

With fuel injection systems that I've worked on, the electric fuel pump pushes flow to the injectors, and unused flow is re-directed back into the fuel tank.  This allows the fuel pump to run continuously during engine operation, with unused fuel going through the bypass circuit.  This allows for quicker injector response as it sees max fuel pressure at all times and only allows the injectors to use what the ECM requires for optimum operation.

 

With an electric fuel pump used on a carburetor, what shuts the fuel pump flow off so that the carb needle valve is not forced open, causing the carb chamber to flood?  There are no external sensors involved to control a logic circuit, nor is there a bypass circuit to redirect excess flow.  My guess is that on pumps designed to be retro-fit on fuel systems that had mechanical pumps operating under 10psi, that the sealed electric pump has check valves in it that are similar to the mechanical pumps.  But I don't know for certain, and the Carter 6V pumps I have on the shelf did not have any documentation on operation, just a warning to add an oil pressure sensor for a safety precaution.

Edited December 18, 2013 by JBNeal

[Merle Coggins]

The electric pumps, like a mechanical pump, can only pump up to a certain pressure depending on it's design. Once the float closes the needle valve the pressure builds in the line until it exceeds the limt of the pump and flow stops. When installing an electric pump you need to match the pressure rating to the system requirements, or add a fuel pressure regulator before the carburator to limit the pressure to what the float and needle can handle.

 

Merle

[ggdad1951]

The electric pumps, like a mechanical pump, can only pump up to a certain pressure depending on it's design. Once the float closes the needle valve the pressure builds in the line until it exceeds the limt of the pump and flow stops. When installing an electric pump you need to match the pressure rating to the system requirements, or add a fuel pressure regulator before the carburator to limit the pressure to what the float and needle can handle.

 

Merle

what Merle said...it's all head and pressure to a pump.

[Jerry Roberts]

If you don't already have a flat piece of steel to make a plate , I made a plate from a electrical box cover plate from the hardware store, it was about 4 inch square to start with . Heavy material and cheap . 

[41/53dodges]

Depends on the type of pump! I use what we refer to as a "diddle" pump, which is a solenoid pump that can only pump up to a certain pressure. Modern cars use gerotor pumps that like lots of pressure an no lift, needing a regulator unlike the diddle pumps. For the cover I was lucky enough to find a factory cover, which is pretty thick so it doesnt distor the gasket  

[MBF]

I would suggest some type of inertia switch to turn off the pump if your ever involved in an accident.  W/o that switch the pump will continue to pump until the battery goes dead or someone shuts off the key.   That could be a problem if a fuel line broke, or if the carburator was left in a position where the needle valve can't remain closed. 

[jnicho]

Good info...thanks guys.  Anybody actually make a gasket...or just RTV?

[TodFitch]

Good info...thanks guys.  Anybody actually make a gasket...or just RTV?

Should be able to pick one up at NAPA. Sorry, don't have a cross reference number for it.

 

Worse comes to worse, get some gasket stock material and a cut one out.

[pwrwgn]

You can also gut the mechanical pump and reinstall it with a heavy, solid gasket. I did this with my Power Wagon and still have a fuel line running into and exiting the stock mechanical pump so it all looks original. In actuality though, the mechanical pump is not operational, and I am running an electric fuel pump located as close to the fuel tank as possible. You want to mount your electric pump close to the gas tank as most pumps are designed to "push" fuel, not "pull" fuel.