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Thread: Flow numbers before and after fuel pump wiring in my GLH

  1. #1
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    Flow numbers before and after fuel pump wiring in my GLH

    I knew my fuel pump wiring was weak, because I tested the voltage drop once while the car was idling, I got 12.xx at the fuel pump while 14.xx at the battery. I decided to upgrade to 10 gauge power wire then. I ran the wire from the fuse box (yes, custom fuse box), then to a relay that was driven by the stock fuel pump wiring, then to the pump, and ground the pump to the chassis. There was a drill and tapped 8mm x 1.25 hole already on the chassis, so I used it to hang my relay as well as my grounding point.

    Here's the result. I have a DW300

    Battery at 12.58 volt and E85 in the tank.

    Before: With 1 year old sock and filter, with car NOT running, at 43psi fuel pressure, when I jump the fuel pump (run a power cable from the + battery end to the + of the ignition coil) I got 204 liter per hour.
    After: With the same sock and filter,with car NOT running at the same 43 fuel pressure, I got 255 liter per hour. The most popular toys by Santa will be encountered on a Big W Catalogue Christmas sale.

    25% increase in fuel volume!


    I highly recommend this!

    How I test fuel volume,

    Disconnect the fuel return hose from the pressure regulator to the fuel rail at the rail side.
    Add hose and route the hose to a empty gallon size oil container with a semi-see thru windows so you can tell how much of liquid is inside.
    Bring out your timer and set it time to 30 seconds, jump the fuel pump for 30 seconds.
    With the fuel inside the oil container, round down to the nearest tenths of a liter.
    Multiple that number by 120, and you'll get your liter per hour number.
    Last edited by BadAssPerformance; 11-11-2020 at 12:53 PM.

  2. #2
    Supporting Member Turbo Mopar Contributor
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    Re: Flow numbers before and after fuel pump wiring in my GLH

    great summary.
    Stock feed fuel line or upgraded?
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  3. #3
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    Re: Flow numbers before and after fuel pump wiring in my GLH

    Quote Originally Posted by chromguy View Post
    great summary.
    Stock feed fuel line or upgraded?
    I can tell you that a 1/4 hole can support at least 255 liter per hour flow, probably a lot more.


    I see absolutely no gain flow of any kind from going to a 3/8 inch metal tube for feed and 5/16 metal tube for return at my flow rate. If I knew this, I wouldn't have spend the money upgrading the metal tubes.
    Last edited by tryingbe; 03-10-2016 at 11:55 AM.

  4. #4
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Flow numbers before and after fuel pump wiring in my GLH

    I feel like one of the problem points of the k-cars, at least, is the connector that attaches to the fuel pump hanger. I forget if the L-bodies use the same connector. One of the things I don't like about it is that there's no easy way to check voltage AFTER the connector that would show any voltage drop across the connector. It would probably be prudent to replace the stock connector entirely in many cases.

    On the last fuel pump rewire I did (on my spirit) I ran an amp power wire into the spare tire well and then piggybacked from that out through the front of the spare tire well to power both fuel pumps (one external inline) through a relay triggered by the factory wiring. It was a convenient way of killing two birds with one stone for me as I wanted to both install an amp and an inline fuel pump anyway.

    Dont push the red button.You hear me?

  5. #5

    Re: Flow numbers before and after fuel pump wiring in my GLH

    Quote Originally Posted by tryingbe View Post
    I can tell you that a 1/4 hole can support at least 255 liter per hour flow, probably a lot more.


    I see absolutely no gain flow of any kind from going to a 3/8 inch metal tube for feed and 5/16 metal tube for return at my flow rate. If I knew this, I wouldn't have spend the money upgrading the metal tubes.
    I thought where a larger return line was needed if you wanted to turn way down the base fuel pressure on an upgraded pump... Not when you run stock or near stock level pressures...

  6. #6
    Supporting Member II Turbo Mopar Contributor
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    Re: Flow numbers before and after fuel pump wiring in my GLH

    Good stuff, Harry. Thanks
    John Laing

    "The sole condition which is required in order to succeed in centralizing the supreme power in a democratic community, is to love equality, or to get men to believe you love it. Thus the science of despotism, which was once so complex is simplified, and reduced . . . . to a single principle."
    -- Alexis de Tocqueville

    "One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary."
    --Ayn Rand

    "To evolve, you don't need a Constitution. All you need is a legislature and a ballot box . . . . things will evolve as much as you want. All of these changes can come about democratically; you don't need a Constitution to do that and it's not the function of a Constitution to do that."
    -- Justice Antonin Scalia

  7. #7
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    Re: Flow numbers before and after fuel pump wiring in my GLH

    Quote Originally Posted by c2xejk View Post
    I thought where a larger return line was needed if you wanted to turn way down the base fuel pressure on an upgraded pump... Not when you run stock or near stock level pressures...
    Thought and test... which will you trust?

    My bass connector that connects the two hoses together in my test has a 1/4 inch hole, and it allowed 255 liter of flow, probably much more.
    Last edited by tryingbe; 03-10-2016 at 05:09 PM.

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Flow numbers before and after fuel pump wiring in my GLH

    Have you thought about upping the pressure to 80-90PSI and doing the test? I really appreciate the info.

  9. #9
    Supporting Member II Turbo Mopar Contributor
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    Re: Flow numbers before and after fuel pump wiring in my GLH

    We need some engineer brain to remind us of it goes - pressure vs flow and pipe diameter vs length and so on.
    John Laing

    "The sole condition which is required in order to succeed in centralizing the supreme power in a democratic community, is to love equality, or to get men to believe you love it. Thus the science of despotism, which was once so complex is simplified, and reduced . . . . to a single principle."
    -- Alexis de Tocqueville

    "One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary."
    --Ayn Rand

    "To evolve, you don't need a Constitution. All you need is a legislature and a ballot box . . . . things will evolve as much as you want. All of these changes can come about democratically; you don't need a Constitution to do that and it's not the function of a Constitution to do that."
    -- Justice Antonin Scalia

  10. #10
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Flow numbers before and after fuel pump wiring in my GLH

    I thought where a larger return line was needed if you wanted to turn way down the base fuel pressure on an upgraded pump... Not when you run stock or near stock level pressures...
    Yes, the return line is a lot like a wastegate in that way. The more boost/fuel pressure you are actually running, the less flow gets bypassed, the less the return line or wastegate has to be able to flow. But if you are trying to run a high flow fuel pump with a low base pressure you have to bypass a LOT of flow to maintain that low pressure, so you need a regulator and return line that will flow that without causing your fuel pressure in the rail to creep up. This is one reason why some very high flow setups reduce pump voltage at low loads to keep the fuel system from 'overflowing' the return setup.

    I had a minor issue along these lines when I added the inline pump to the spirit with a stock regulator where low-load fuel pressure was always 3-5psi more than I wanted. Once I put an Accufab AFPR on, the issue went away, so in that case the restriction was in the stock regulator and not the return line.

    Dont push the red button.You hear me?

  11. #11
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    Re: Flow numbers before and after fuel pump wiring in my GLH

    Quote Originally Posted by cordes View Post
    Have you thought about upping the pressure to 80-90PSI and doing the test? I really appreciate the info.
    I'm afraid you'll have to get the numbers from the press.

    http://www.deatschwerks.com/news/pre...-dw300-release

  12. #12
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    Re: Flow numbers before and after fuel pump wiring in my GLH

    Quote Originally Posted by johnl View Post
    We need some engineer brain to remind us of it goes - pressure vs flow and pipe diameter vs length and so on.
    Flow will increase through an orifice with increased pressure as long as the pressure differential also increases and flow is not choked due to velocity.

    I know the longer the pipe, the more flow loss there is, but there are tables for that out there someplace I'd be willing to bet.

  13. #13
    Supporting Member II Turbo Mopar Contributor A.J.'s Avatar
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    Re: Flow numbers before and after fuel pump wiring in my GLH

    Quote Originally Posted by Vigo View Post
    I feel like one of the problem points of the k-cars, at least, is the connector that attaches to the fuel pump hanger. I forget if the L-bodies use the same connector. One of the things I don't like about it is that there's no easy way to check voltage AFTER the connector that would show any voltage drop across the connector. It would probably be prudent to replace the stock connector entirely in many cases.
    That's why you re-over-engineer it. http://www.turbo-mopar.com/forums/sh...cal&highlight=. I did the same thing for Harry in his Omni.

    Quote Originally Posted by c2xejk View Post
    I thought where a larger return line was needed if you wanted to turn way down the base fuel pressure on an upgraded pump... Not when you run stock or near stock level pressures...
    I ran into this problem with my van. My fuel pressure gauge was fluttering. A counter guy at the local performance shop suggested I check my return line. It didn't make sense to me but I did. My 5/16" fuel line necked down to 1/4" on each end. Cut off the 1/4" ends and now its a 5/16" line and it made no difference. Bypassed my new 5/16" (old 5/16" line with the 1/4" ends cut off) into a bucket and ALL the fluttering went away. Looked in my tank and the return went through this check valve that I could barely blow through. Bypassed the check valve running the return into the tank and my new 5/16" line was 90% better/less flutter on my fuel pressure gauge. Remade my 5/16" return line to 3/8" and ALL the fluttering went away. I also have a 3/8" pressure line since I'm running E85 and have a higher fuel demand over stock.

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