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Alternator to power fuel pump? [message #370436]

Thu, 01 September 2022 19:24

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

I am installing a pair of Carter pumps. I have been thinking of way to be sure they don't run when the engine is not.
For some time, I have been feeding the electric choke heater off the alternator output and that has been really successful.
Can anybody think of a good reason why I can't pull more power off that same place on the isolator to feed the selected fuel pump?
Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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Re: Alternator to power fuel pump? [message #370437 is a reply to message #370436]

Thu, 01 September 2022 19:40

JohnL455

Messages: 4447
Registered: October 2006
Location: Woodstock, IL

Karma: 12

Senior Member

It depends how the pumps like 14-15 Volts. Probably fine.
Issue is pre run for the pumps and if alternator output will run the pumps during cranking. Personally I would use the alternator to drive a relay coil which then gives normal system voltage to the pumps. You could add a momentary switch to latch the relay using engine batt power to prime or during cranking.

John Lebetski
Woodstock, IL
77 Eleganza II

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Re: Alternator to power fuel pump? [message #370438 is a reply to message #370436]

Thu, 01 September 2022 21:23

RF_Burns

Messages: 2276
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

Matt,

The only concern I would have is the voltage present at the alternator output (isolator input) would be rectified 3 phase power. There would be no filtering and smoothing that is usually facilitated by the battery. I'm not sure how that would affect the pump motor, especially if it is a brushless motor.

Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

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Re: Alternator to power fuel pump? [message #370440 is a reply to message #370436]

Fri, 02 September 2022 02:51

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

I am with Bruce on this one. Noisy power there and no power during normal cranking to run the pump.

Ken B.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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Re: Alternator to power fuel pump? [message #370441 is a reply to message #370436]

Fri, 02 September 2022 05:29

winter

Messages: 247
Registered: September 2007
Location: MPLS MN

Karma: 0

Senior Member

Will you have the ability to run the fuel pump if the alternator dies on the road? May require a bypass.

Jerrod Winter
1977 Palm Beach
Green Jelly Bean
Twin Cities, Minnesota

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Re: Alternator to power fuel pump? [message #370442 is a reply to message #370436]

Fri, 02 September 2022 06:28

RF_Burns

Messages: 2276
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

Matt,

Just use the alternator voltage to power the coil of a cube relay. Then pass the power from the battery through the relay to power the pumps. A push-button momentary switch can give you a prime function before starting the engine. If the alternator fails, simply move the power wire from the N/O to the N/C side of the relay.

My coach has Daytime Running Lights which are activated through a relay wired this way.

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Re: Alternator to power fuel pump? [message #370443 is a reply to message #370442]

Fri, 02 September 2022 10:08

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

I want to thank all that answered. All of the replies were valuable.

What I really want an set up where the fuel pump can't run with the engine off. I considered lots of things like NO LOP switch, but I don't have one on the shelf.

The Carter 4070s have been around for a long time and they can't be brushless, they are just too old. They can't be too voltage sensitive because some of the applications where they have been were really strange voltage wise.

My plan is to use the current selector valve switch to control a standard ISO cube relay as they are SPDT. Energized will put power to the Auxiliary pump.

What I like about this plan is:
1-The relay is in my stock
2-There is only one component in the control system.

For background, I have a diagram drawn up for a control system with a multi diode AND gate (True and not AND/OR), a delay relay three relays. Yes this provided an auto prime feature for starting, but it has a dozen components and fourteen failure modes. (Yes, I wrote a quick FMEA.)

As it turns out, 23footers don't have a lot of room to mess with putting these things in. The gas tanks are 4 feet closer to the engines, so I'm planning to mount the pumps to the underside of the wood floor.

I will be sure to let everybody know how this works out.

Matt

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Re: Alternator to power fuel pump? [message #370444 is a reply to message #370436]

Sat, 03 September 2022 14:09

jhbridges

Messages: 8412
Registered: May 2011
Location: Braselton ga

Karma: -74

Senior Member

May I suggest, either through bolt them, or run a screed side to side to attach them. Anyway, something to ensure that they don't fall off. Look in the photos at my album called cane creek or something with that in the name. The first few pictures are 'fuel pump follies' . That's a 23', they're Mr. Gasket pumps, but samesame. I wonder if it hurts them to deadhead? I'd use this same setup and feed the high pressure pump from them. They deadhead off and on, but for how long?

--johnny

Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons. Braselton, Ga. I forgive them all, save those who hurt the dogs. They must answer to me in hell

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Re: Alternator to power fuel pump? [message #370446 is a reply to message #370444]

Sun, 04 September 2022 22:06

Bullitthead

Messages: 1411
Registered: November 2013

Karma: 5

Senior Member

The floor is a big speaker board for fuel pumps, even when mounted through rubber isolators. Found out the usual way, but at least I know when it's running. Choose your mount carefully and try it for noise before you button it all up. Relay power from alternator with override switch and indicator light is the way to go.

Terry Kelpien ASE Master Technician 73 Glacier 260 Smithfield, Va.

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Re: Alternator to power fuel pump? [message #370447 is a reply to message #370446]

Mon, 05 September 2022 07:36

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Bullitthead wrote on Sun, 04 September 2022 23:06

The floor is a big speaker board for fuel pumps, even when mounted through rubber isolators. Found out the usual way, but at least I know when it's running. Choose your mount carefully and try it for noise before you button it all up. Relay power from alternator with override switch and indicator light is the way to go.

Terry,

There is concern about the pump noise, but this coach is a 23 so the auxiliary tank is real close to the torsion bar cross member and that leaves little room to much other than mount them to the floor that I can see. There is an owner had mounted his fuel pump system on a hinged piece of aluminum that can be lowered. I really wanted to do that too, but there just is not room where they have to be in this coach. There was a plan to mount them outside the frame rail, but my parking brake worked recently and I want to get it back.

In my original plan, I had a delay circuit to run the fuel pumps on the starter, but I don't have the time in this program to include that.

Thanks to all

Matt

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Re: Alternator to power fuel pump? [message #370469 is a reply to message #370436]

Sat, 10 September 2022 17:15

jhbridges

Messages: 8412
Registered: May 2011
Location: Braselton ga

Karma: -74

Senior Member

Matt, here's my solution on the 23' coach. I used Mr. Gasket, but you could use the Cqrter ones as well.

http://www.gmcmhphotos.com/photos/g6198-cane-9-creek-rv-park-heflin-2c-al.html

These pumps had internal backflow prevention, sos all you gotr to do is tee the output.

OIl switch as a shutoff. Since it's carbureted, you don't need a prime switch.

--johnny

Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons. Braselton, Ga. I forgive them all, save those who hurt the dogs. They must answer to me in hell

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Re: Alternator to power fuel pump? [message #370470 is a reply to message #370469]

Sat, 10 September 2022 17:44

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Johnny,
I guess that you did away with the engine driven pump altogether.
The Mr.Gasket version of a clicker pump is what I have had on the shelf for a while. I put it in line with the auxiliary a day ago and got to test it today. We still had vapor lock issues that instantly disappeared when I stitched to the Aux tank. In my history, I had had some failures with those pumps and I have had problems with both the OE tank selector as well. That is why my plan is to mount two 4070s under the floor and use them as the tank selector. That also gives me a redundant system. I see you have that too.
I had plans to put back the wrong pump that has a vapor bleed, but I don't think I am going to have to go that far based on today's experience.
Matt

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Re: Alternator to power fuel pump? [message #370497 is a reply to message #370436]

Tue, 13 September 2022 12:55

jhbridges

Messages: 8412
Registered: May 2011
Location: Braselton ga

Karma: -74

Senior Member

One picture shows the blank flange on ther block, and the connector threaded onto the carb feed hardline. I capped the selector valve and ran the relay with the valve feed. You could revert to OEM beside the road in half an hour if you wanted.

Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons. Braselton, Ga. I forgive them all, save those who hurt the dogs. They must answer to me in hell

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Re: Alternator to power fuel pump? [message #370498 is a reply to message #370497]

Tue, 13 September 2022 20:57

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

jhbridges wrote on Tue, 13 September 2022 13:55

One picture shows the blank flange on ther block, and the connector threaded onto the carb feed hardline. I capped the selector valve and ran the relay with the valve feed. You could revert to OEM beside the road in half an hour if you wanted.

My selector valve died years ago and the only available replacement part is upside down and backwards so it is not in the same place. I have also (along with having the engine throw all its belts) found the pressurizing the fuel line that was negative pressure may cause leakage where one was before.
I am going to end up with two independent fuel pumps that can be selected with the tank switch and if there is still one pump and an alternator (if the belt is still on it), I should be able to pump fuel out of the tank. I do not plan to remove the engine fuel pump, but I may change back to the other pump that includes a vapor bleed.
Matt

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