Fuel System: Recommendations for a 6V electric fuel pump

[LeoH]

I'm planning on getting an electric fuel pump for my 2R17 and bypassing the original pump. I'm leaving that in place and sealing off those fuel ports.

Other than getting a pump with a 4-5# pressure, any recommendations? Are the Airtex pumps acceptable?

[64V-K7]

These have a good track record

http://www.summitracing.com/parts/atx-e8902

[LeoH]

Good to hear, thanks. I saw those, and have been reading a little and hadn't come across anyone having a problem with them at least.

[Mike Van Veghten]

Carter P4389.
It's a 12 volt pump, but mines been working on 6 volts for for over 2000 miles without problem.
Just swapped the pos., for the neg. posts for the positive ground.

Mike

[LeoH]

Interesting Mike, what caused you to decide to do that?

[Mike Van Veghten]

An experiment.
It worked.

Since a motor basically works off of the amperage (not so much volts) available to it. Even though a 6 volt system provides more amps than a 12 volt system, it's "available", not "forced" into the motor. The motor will only draw what it needs, amperage wise. The additional amperage just sits in the battery until something else needs it.
And...having a lot of experience with small DC motors, and realizing that putting fewer volts into a motor does not hurt it in any way... I just put those two facts together, and plugged in my 12 volt pump into a 6 volt battery.

Actually, one thing did surprise me. The fact that the pump put out the "advertised" 12 volt pressure...at 6 volts..!

For the record, small "jumps" in voltage will not normally hurt either. Putting 12 volts to a quality 6 volt motor will just spin it faster. But 18 volts won't last so long.
I ran a pair of OLD...6 volt horns in a 12 volt system. Lasted for (as I recall!) 4 or 5 years before finally failing.

Mike

[nvonada]

What problem are you trying to solve with the electric pump?

[LeoH]

What problem are you trying to solve with the electric pump?

Not buying a rebuild kit, disassemble the existing fuel pump rebuild it and not have it work anyway. I'm leaving the pump in place to run as a vacuum pump for the wipers.

I don't have an electric pump on my daily driver Lark wagon and I notice the difference when I let it sit a day; on an older 6V truck, not garaged, in winter but wanting to be able to drive it without excess troubles after it sits for a few days, the $40 or so for an electric pump that bypasses the pump is what I want to do for now. If the truck turns out to run fine and be dependable, I'll consider getting a rebuild kit later and leave the electric pump in as an assist to the mechanical pump. My goal now is to just see if the truck runs and get it to a point where it runs reliably, I think the electric pump is a cost effective decision for now.

[gordr]

Mike, motors tend to regulate themselves due to "back EMF". As they run, they also generate a voltage that opposes the applied voltage. These little DC motors, lightly loaded are pretty tolerant of under/over voltage. Not so bigger AC motors. Undervoltage causes reduced back EMF, which means they pull more current, while delivering less power. You can easily kill appliance motors with chronic undervoltage.

And any electric motor that stalls, while still being fed with power, will burn out right quick. Starters being a good example.

[LeoH]

I have a pump on order, but I'm definitely weak in the electrical accessory add on skills, particularly important accessories. I have fair to decent wiring in the instrument panel and I'm going to have to fabricate some sort of mount on or around the Hill Holder for the pump, but when it comes to wiring it in the dash, other than knowing the power lead needs to go to the hot side of the ignition post and that the ground should go to the frame somewhere, that's it. If the pump doesn't come with a separate fuse, could someone tell me which size inline fuse I need to insert? Also if there's any other wiring tips I need to know, it would be appreciated.

[Mike Van Veghten]

gord -

Understand.
But we are talking small DC motors. Small being up to and including automotive engine starter motors. I've seen 6 volt starters run a full (drag race) season powered by 24 volts.

MANY years...ago, I had a small 8 volt motor in a drag race slot car. I was at a big national road race event, but wasn't racing. Though I did bring one car that everyone liked to watch on the drag strip. It was 25 cents per run, and I was collecting money by the hand fulls.
Well the "rich" kid (always one in the crowd) wanted me to up the voltage from 12 volts (as I recall, the power was rated at 200 amps). We went to 18 then to 24. The car made a lot of 24 volt runs without any visual problem. Then the rich kid came back and wanted to see it at 32 volts. I said no. He said ok, run it at 36 volts (the max.) and I'll pay for a new motor if it blows up. I knew he was good for it...so I cranked the power to 36 volts.
The car left sideways like a rocket. The car got to about three feet from the starting line, a blue flame shot out from under the car and it came to a skidding halt..! The damage was such that it wasn't feasible to try to fix that motor. "Bill" bought me a new motor right then and there.
The little 32 Ford coupe was a bigger hit than ever..!

Mike

[gordr]

Yep, you can get away with over-volting DC motors. Under-volting, not so much, particularly under load. When do you burn out a starter? Not when it has plenty of juice and spin like crazy, but when the battery is low and it barely turns, or not at all. Keep current flowing into a stalled motor, and it will burn out. I would hesitate to run a 12 volt windshield wiper motor on six volts.

[RadioRoy]

I have a pump on order, but I'm definitely weak in the electrical accessory add on skills, particularly important accessories. I have fair to decent wiring in the instrument panel and I'm going to have to fabricate some sort of mount on or around the Hill Holder for the pump, but when it comes to wiring it in the dash, other than knowing the power lead needs to go to the hot side of the ignition post and that the ground should go to the frame somewhere, that's it. If the pump doesn't come with a separate fuse, could someone tell me which size inline fuse I need to insert? Also if there's any other wiring tips I need to know, it would be appreciated.

Hook the pump to the accessory terminal on the ignition switch. That way, you can run the pump to prime the carburetor before starting the engine. The ignition key should never be left in the "on" position unless the engine is running or being started.

[LeoH]

So, progress, but since I don't have a radiator until later this week or next (fingers crossed), I just did operations testing basically.
The pump switch for now is wired to the battery directly, with an inline fuse. One detour today was hooking things up and no sound from the pump. Hm. Talking with the friend who's shop I'm at, we were down to thinking the switch was bad or one of my connections in the wiring was not adequate when it dawned on him, "Positive ground, which wire did you ground?" Of course, the black ground wire, so back I went, switched wires, flipped the switch and whirring commenced. I installed the switch in the starter button hole on the dash next to the choke lever.
I did prime the pump as best as I could with a funnel before firing up. I also ran the engine without plugs in to oil up the block as this is a six and the oil pump is not run off the bottom of the distributor.
It does turn over, sounds like it has compression and gas is squirting in the carb, so we checked the coil and distributor. The ignition and distributor wire to the coil were both crispy and cracked, so I had replaced them before trying to start the engine, but I had to tear the harness apart a few inches in order to free up enough ignition wire to connect to in good shape.
The rotor and points looked newer, good enough they should have done some firing. We checked the ignition wire and didn't seem to get any juice to the splice, so likely there's another part of the ignition wire that's toast.
I think I'm just going to quit while I'm behind and get a new harness. It's not that much money and will be time saved in chasing down subsequent shorts were I ever TO get the engine firing off the old wiring.
The starter switch worked, the starter turned over, the pump pumps, so those are positive steps in the resurrection.
I did remove the 3 nuts on the back of the dash and the 2 screws holding the speedo/instrument panel in, but I'll be darned if I could figure out how to get the dash panel they rest in loose. I'd have done more fidgeting with the ignition switch if I had better access to it, other than removing the climatizer box.

Also, if anyone's used a particular website to follow how to add a fuse block, I might give that a try when installing the wiring harness while I was at it. So far, the only suggestions I've received from people who have done it was, 'you get a fuse block, put it in and run your wires out of it.' Not detailed enough help for me.
I do plan to get the 6V alternator and I'd like to add a pair of driving lights at least, so having a fuse block would make things safer and easier.

[nvonada]

Leo,
First the fuse block. The fuse block really is that simple. You run battery power (negative in your case) to one side of the fuse then connect the circuit you wish to protect to the other side. Any short or overload on the protected circuit will then blow the fuse and disconnect the battery. This picture shows a typical fuse block. Big cable connects the battery to a buss bar that feeds all the fuses. Smaller wires are going out to the protected circuits.

Did you check for spark? Before you start gutting your wiring realize that almost always when a car will not fire it is plugs, points, or ignition wires. If you suspect the wiring harness a jumper wire directly from the battery to the coil will rule that out. A cheap multimeter is a huge help in troubleshooting wiring. I don't want to be too blunt but if you don't know how to wire a fuse a new harness will be a very rough road. That is a big job and odds are that is not what is keeping you from running.

Nathan