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Author Topic:   Return line pumps

Posts: 591
From: Sarasota, Fla. USA
Registered: Jun 99

posted 12-16-2001 08:17 PM     Click Here to See the Profile for Gary   Click Here to Email Gary     Edit/Delete Message   Reply w/Quote
This type of pump, just what do they do different than another pump that has no return? Would think one by-passes within the pump while the other by-passes back into the tank..right? Another question, on fuel cells with red 3"filler caps, is the cap vented or do you have rely on a separate vent on top of tank? Reason I ask, on my alum. cell I have the cap and a separate hole fitting and sending unit. At this time I have the vent tube attached to the fitting on top of tank figuring that was what that was for. I see what appears to be vent holes on the cap itself and wondered if I can use the fitting Im now using as a vent for a return line instead? Not that im planning on swapping pumps again but this deadhead system I have leaves me in question if Id be better off with that return line pump and then use two regulators, one for each carb.
Seems it would eliminate the cavitation problem I seem to be having and may keep me from losing my prime of the pump..humm?

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Posts: 9936
From: Lyons, IL, USA
Registered: May 99

posted 12-17-2001 11:18 AM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
A by pass pump is designed to eliminate cavitation Gary. What it does simply is when it senses resistance it blows off excess fuel via the by pass and sends it back to the tank. This way you can use 19# pressure ultra high volume pumps on carbureted engines without blowing the needles off of the seats.

Alex Denysenko
Co-Administrator and Moderator
NHRA and IHRA SS/LA National Record Holder '00 & '01
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Posts: 41
From: pittsburgh,pa.usa
Registered: Jul 2001

posted 12-17-2001 08:46 PM     Click Here to See the Profile for mustang68mustangs   Click Here to Email mustang68mustangs     Edit/Delete Message   Reply w/Quote
Alex ,I always thought that it is better to use a bypass reg. with a return line back to the tank. It will keep the pump cooler instead of using the pumps bypass.I have mine hooked up just using the pumps bypass now, but I am going to run a return line and use a bypass reg. because I find that my pressure creeps with the deadhead the fact that I use my car on the street alot.
Gary I have a Harwood cell that is plastic and it has the same cap but I dont think the cap is vented but I could be wrong there is a little metal fitting that could possibly be a vent .But I still have mine vented from the top of the cell.Does your tank have 2 fittings on the bottom? If so use one of them as a return line fitting.If not you can always drain the tank and drill another hole in the cell and use one of those fittings with the locknut and plastic washers. Just make sure you clean out the metal shavings really good.

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Posts: 549
From: Spencer, WV
Registered: Jan 2001

posted 12-17-2001 09:19 PM     Click Here to See the Profile for n2oMike   Click Here to Email n2oMike     Edit/Delete Message   Reply w/Quote
Some electric return style pumps have an outlet that runs an actual line back to the tank. They provide the benefits of a return style regulator without all the extra plumbing of an extra line all the way from the engine to the tank.

I use the Mallory 140 pumps with a return style regulators. Yes, there are four lines running between the tank and engine! It's a nice "geroter" style pump. The geroter is the same design as the Ford style oil pump, and provides a nice, constant, smooth output. They don't make nearly as much noise as the rotary-vane Holley blue pumps, either. One pump has been on the car for 9 years, the other has been on there ever since I started playing with nitrous around 7-8 years ago.

A return style pump or regulator is definitely the way to go. Just be sure to keep the pickup submerged in gasoline. My sump is in the rear of the stock tank, but doesn't really hang down. If I brake hard with less than 1/4 tank of fuel, my fuel pressure fluctuates, and at times the pump will become unprimed, and I've got to crack the line at the regulator to get the pump to re-prime itself. You front-facing sump concerns me. This is why I mentioned running a "siphon tube" to the rear of your fuel tank for the fuel pickup in an earlier post. You'll also want to keep the tank plenty full.

To make the pump whisper quiet, do like someone else mentioned, and mount it on an exhaust hanger.

Good Luck!

Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3

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Posts: 591
From: Sarasota, Fla. USA
Registered: Jun 99

posted 12-17-2001 09:20 PM     Click Here to See the Profile for Gary   Click Here to Email Gary     Edit/Delete Message   Reply w/Quote
Bob, yes I have two fitting at the sump and only using one at this time. Thats good, I can use that outlet for my return. Sounds like a plan Im still deciding on using two regs though, Im using a fuel log and would like to retain it, im thinking of up-grading the single high capacity reg. that can handle more fuel---this is mainly a street car Thanks for reminding me about the dual sump fittings, I only have the single one on top for the vent tube and would rather not have to drill or weld on it....let alone take it back out of the car.
If going from the top they offer a tube to go in the tank for returning fuel to keep the fuel from splashing back and causing air that may get sucked back up by the pump.

[This message has been edited by Gary (edited 12-17-2001).]

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