Automatic Electric Fuel Pump

[Jeff Rosansky CLC #28373]

I did a quick search but did not see anything so I apologize if this has been covered before.

I keep seeing debates on electric vs non-electric fuel pumps. I see the argument for both. Having an electric on a toggle switch works but would/may be a pain to hit at an inopportune time. What about an automatic electric pump that turns on when pressure is low?
I found this https://www.pegasusautoracing.com/productdetails.asp?RecID=2980 .
I know this is for a light, but what if instead of turning on a light it turned on the fuel pump?
Turn the key on and pressure is low so the electric comes on which would prime the system. Then as the mechanical comes alive it would kick off. When in traffic and vapor lock starts to happen fuel pressure would drop and at say 3psi (that is why adjustable would be nice) the "light/pump" would kick on and build pressure before the bowl is dry. You would keep going without ever knowing there was a problem?
It would have to be wired thru a relay I would think but it doesn't seem that hard.
What do you think?
Jeff

[bcroe]

The safety issue is that in case of an accident, the pump could continue
to empty your entire tank into a potential fire.  So they are always rigged
to shut off if the engine isn't turning.  For a carb there might be an oil
pressure switch that must be satisfied to run the pump; EFI always
depends on engine rotation signals.  For just a quick start I think a
momentary only button would be OK; no toggle switch.  Bruce Roe

[Jeff Rosansky CLC #28373]

Oh yes. I am thinking oil pressure and inertia switch too for safety. But the concept sounds good to me.... in theory anyway.
Jeff

[bullet bob]

Jeff. I'm thinking you should be our 'guinea pig' and try this! Would this just thread into the outlet side of the fuel filter?

[Gene Beaird]

The safety issue is that in case of an accident, the pump could continue
to empty your entire tank into a potential fire.  So they are always rigged
to shut off if the engine isn't turning.  For a carb there might be an oil
pressure switch that must be satisfied to run the pump; EFI always
depends on engine rotation signals.  For just a quick start I think a
momentary only button would be OK; no toggle switch.  Bruce Roe

Cadillac EFI may require engine rotation signals to run the pump, but many GM EFI vehicles used the oil pressure switch.  That's now the pump on our 92 Camaro runs.  No oil pressure, no pump, after the standard 3-second pump run at key-on. 

[Jeff Rosansky CLC #28373]

I have the oil pressure switch on order and plan to get an inertia switch as well.
I think the electric would have to be the type that is free flowing when it is off do that the mechanical can run all the time without having to run a 2nd line. The pressure switch would need to be after the pump.
Jeff

[G Pennington]

These oil and fuel pressure sensors are usually designed to operate idiot lights (or to provide a signal to the computer on newer cars).  That means the internal contacts are designed to handle low current.  I personally would not wire a fuel pump directly to the sensor.  I would use a relay or some other control device.  Not sure about the inertia sensor.

[TJ Hopland]

Starting around 75 to the end of carbs GM used a 3 pin oil switch where 2 pins switched the power to the electric choke.   That is why you had an oil/choke light.   
   
GM tried running the pump direct off the switch a few times and it didn't work well.  No idea why they thought it would work.  It was really dumb since there was already a relay controlling the pump in the system for cranking.   It would have been easy for them to make the crank relay connect to the oil pressure switch.   

I don't have time to search at the moment but places like Jegs and Summit sell a kit that has the pressure sensor, relay, and a universal harness.

[fishnjim]

It depends on what you're trying to accomplish, overcome, or replace and on what.
The problems people run into are not that one type is better than the other but from ill functioning fuel systems and problems with modern fuels.   Changing pumps alone won't necessarily fix that nor be the sole answer.   But according to the reviews on that page, this will do what is intended, fuel pressure control 2-7 psig, if properly set-up and wired.  Respect the rated contact amperage, etc as noted by others.
If you are trying to overcome some operational or condition issue, then define it and why it occurs, and if it can be corrected before you change the design.   This is how things get messed up/overly complex, adding too many layers of controls for easily solvable problems.
When I got my car the previous owner had installed a new fuel tank and electric pump incorrectly and the mechanical was actually doing all the work but most of the problem was contamination/pluggage.   After cleaning/replacing/fixing the whole system, it performed well without the electric.

[tturley]

I put an AirTec pump directly inline close to the tank with a toggle switch under the dash. I only use it if the car had set for a very long time and then only for about 5 or six seconds.
I see it as an insurance policy should I experience vapor lock or mechanical pump failure

[Gabe Davis]

I was experiencing vapor lock issues on my '59 and needed an electric pump to help with the carb running out of fuel due to bubbles in the line. It would usually happen on a hot day after sitting in traffic at a stop light. Like Tom, I also used an AirTec pump. It will still flow even without power so the manual pump can draw fuel like it was not there.

I wired in a relay and a single pole double throw switch with an "off" position at center. The first "on" position of the switch is used to prime the system after sitting for a long period. It is connected to a fuse in the block that has battery voltage regardless of the position of the ignition switch. I did this to try to be a little easier on the points when priming the fuel system when the engine was cold and had sat for a long time.

The center position of the switch is "off" and can be used to disable the electric fuel pump when running. Fuel will still be delivered to the engine via the mechanical pump.

The remaining "on" position of the switch is tied to the relay. The relay has a normally open and normally closed position. The voltage feeding the relay is tied to a fuse that only has positive voltage when the ignition switch is in the run position. The coil of the relay is tied to the same positive voltage feed. The other side of the coil is tied to the oil pressure sensor (a dark blue wire on the '59) which connects to ground when oil pressure is present. When the oil system builds pressure the relay is engaged and the electric fuel pump is activated.

I set it up in this way so that when the engine loses oil pressure the relay will disengage and disable the electric pump. I'm sure I could augment this setup with an inertia switch for even greater safety.

As far as adding a system that engaged when the fuel pressure is low, perhaps you could use a setup similar to mine only tie the relay in such a way where a pressure sensor in the fuel line on the carb side of the fuel pump would engage the electric pump if the pressure was low.

Of course, this is presuming that vapor lock does not cause a low pressure situation to occur. I'm not up on the physics of vapor lock. It may actually increase the pressure in the fuel lines, making the passing of fuel and the reading of pressure impossible to measure accurately. All I know is that with my setup I have not run into the same stumbling and stalling issues that I had before the electric pump helped push things along. Simply toggling the switch to the run position manually when the car began to stumble has saved a stall each time.

It may also be important to note that I added the smaller fuel return line from the fuel filter to the tank. My car does not have AC from the factory and only had a single feed fuel line. In my process of trying to reduce the vapor lock issues I added the fuel return line that was present in cars that came with AC from the factory. This necessitated an change of fuel filter setup, matching the factory AC parts to facilitate the return fuel line. I'm not sure how that would affect fuel pressure but it ensures a constant flow of cool fuel from the fuel tank to the filter bowl.

Good luck with your setup!

[Jeff Rosansky CLC #28373]

This is kind of my thinking with 1 addition. Pump normally on but goes thru a fuel pressure switch. When pressure drops the fuel pressure switch turns on a light. Except instead of a light the switch trips the relay.
What p/n Airtex pump did you use?
Thanks.

[fishnjim]

Before I spent money, I'd try non ethanol fuel and see if the problem goes away.  It's much more available now.
The distillation curves for ethanol fuel show a large (~30%) non-ideal portion around 50-75C, and is due to minimum boiling azeotropes with some of the gasoline fractions.   The earlier MTBE oxygenates or non oxygenates did not have this issue.   Another thing to blame B. Clinton/A. Gore for...

[cadman56]

On my last two 56's I installed an inline Airtex fuel pump and activated it with a chrome starter push button switch I attached under the dash.  I only used it to prime the system after the car sit for some time.
Maybe this is a different situation than above?
Good luck.

[Gabe Davis]

It has been several years since I installed the pump but I think it may be this model:

http://www.airtexproducts.com/single-product/?partnumber=E8016S&id=98756AX

I remember it having, what I assume is, the pressure regulator screwed to the outlet of the pump. I put it very close to the tank in the space between the tank and where the shelf is in the trunk. That way it will be protected from objects coming up from the road and will prime quickly and push up the lines as it is intended. If I had to change anything I would use better rubber isolation mounts to try to reduce the noise it makes while running. When driving you can't really hear the pump but when priming before the engine is running it is easy to make out.

The installation is easily reversible if a complete stock setup is needed for any reason. I am very happy to have the electric pump to help reduce the possibility of vapor lock and to give some peace of mind while on the road.