Electric Fuel Pump voltage....

.... the wiring post by TwoQuik got me to thinking about a self inflicted problem.

I've been through three Holley street pumps on my 32 and was beginning to wonder about Holley quality.
The last one found me going the 6 miles home on a wrecker cuz the car quit in a sunny spot on a greasy asphalt street on a 105 degree day.
Since I was wearing shorts and a T-short, I wasn't about to crawl under the car and try to replace the pump with the on-board spare. That's a gennie bitch when the car is on clean cement in the shade. Jack it up a touch and life is easy.

The first pump that quit didn't really quit, it just quit regulating. Disassembly and a little polishing of the regulator bore within the pump fixed it very nicely.

The next couple of pumps lasted quite a while and then conked out. The last one as noted above.

I got curious about it and took a voltage read at the pumps hot terminal.
About 11.2 volts.
With about 12.4 volts on the battery and the car not running.

It made sense because the fuel pump wiring left the terminal block source - which was fed from the hot terminal on the Ford solenoid under the seat - went through a dedicated fuse, to a toggle switch, over to the other side of the car where it went through an S-W pressure safety switch (Which kills the circuit when the engine has no oil pressure. The safety switch in case of a wreck. It wouldn't shut the engine down fast enough if oil pressure failed in a non-emergency situation.)

From the safety switch the wiring runs up to the igniton switch and finally back down to the pump. (You can see the safety switch just to the right of the Fram filters. It's tapped into the other side of the dual oil filter adapter that's usually blanked off on the unused side.)

I'm fairly sure I used 16 gage all the way and I should have known better.
14 gage would have been the stuff to use.
I didn't start out to have an overly long elec fuel pump source wire, but like Topsy, "It growed."

Things were squared away by the installation of a constant duty - and constant duty is the key word here - relay that was now controlled by the fuel pumps original wiring.
Ten gage wire was run from the hot side of the Ford solenoid to the relay and 14 gage wire run to the pump.
With the 14 gage being a very short run.
Now the fuel pumps hot terminal wire read 12.4 volts, same as the battery.
The original pump wiring was replaced with 14 gage.
It seems to have helped, the voltage at the relay from the original control (ign sw. etc.) source is about 11.8 volts with the battery still at 12.4 volts.
Once the car is running, battery voltage is 13.2 volts with a comparable rise all other areas.

To top it off, after all this, it was decided to install a mechanical fuel pump and abandon the new S-W pump in place, still wired up, but available for emergencies by simply moving the inlet and outlet hose from the short piece of hose that connects them to the elec pump. There is a ball valve to shut off fuel flow from the tank so the big filter can be replaced so no problems there.

What brought all this about was starting the 32 yesterday morning. I hadn't driven it since December 8th and it took a bit of spinning to fill up the fuel bowl.

Remembering the convenience of the electric fuel pump, being able to shut it off and run the carbs float bowl dry as well as filling it with engine off and when running the Holley carb setting up the float level with engine off, I decided to put the elec pump back in service and retain the mechanical as a backup.
All I'm gonna do to the mechanical is run a loop of hose between inlet and outlet.

For those who saw the fuse array in the seat riser pic in TwoQwiks wiring post, the Ford starter button (two terminal in this case) is a normally open parallel circuit around the safety switch so the carbs float bowls can be primed without mucho cranking on starter to get oil pressure up and then wait for the fuel pressure to come up and then finally starting the car.

In my opinion I don't think it's a good idea to use an electric pump to feed a mechanical.
I knew of one jalopy racer who did that and filled the crankcase with gasoline.
The result - as he put it - was more than interesting....

 

C9 - I have a similar set up in my '55 Mercury. I use the electric pump to fill the carb bowl prior to starting. Then the car runs off the mechanical pump. Basically, my electric pump feeds through the mechanical one. Your last paragraph has me a bit worried. It sounds like if the mechanical pump's diaphragm fails, the electric pump could possibly pump fuel into the crank case. In my case, this could occur prior to starting and I wouldn't really know it happened until after the fact. Hopefully, the engine would die of fuel starvation before anything in the crank case were to happen. I may have to rethink my carb priming system!

 

I'm not sure of the quality of the Holley pump, seems like its hard to get good quality anything anymore. But the voltage drop that you had shouldn't have taken the pump out. You sould be able to go + or - 10% on the motor and never hurt it.

I run a Mallory pump, and had this problem with it. on a 105* day it took a dump on me. It was under a tin cover on the bed of a pick-up I had. If I jiggled the wires and held them just right it would run. So I layed under the cover on the bed and the wife drove home. About 11 miles if I recall.
I took it apart and the carbon from the brushes was everywhere, cleaned it up and haven't had a problem since.
I'm thinking of going to a different setup on the new ride.

 

It seems that most electrical devices tend to fail prematurely if they are not run at the specified voltage.I've had that problem with single speed electric wiper motors in my 55 Pontiac.They are cable actuated(the switch is on the motor)and if you don't fully turn them on the field coils will fry in about 20 minutes of operation.
I think your idea about being way of running the electric pump into the mechanical one has some merit.What about mounting the electric pump at the tank and installing a fuel pump pressure gauge AND regulator BEFORE the mechanical pump?The only reason I suggest this is that the electric pump is capable of putting out much more pressure than the mechanical one and that could conceivably cause a diaphragm to rupture.
Ray

 

C9 had a similar interesting problem, car would develop a flat spot when putting the right foot into it, scratched my head alot, especailly as its 2x2 94's on a flathead played with jets, powervalves etc, turned out to be faulty wiring to the fuel pump, it just wasnt getting enough juice of its own. Funny what a solution to a problem can end up being

 

i still like the mech pumps, electric can be to problematic (and too much wiring). just think of the extra cranking before it starts as oil priming........