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Thread: Fuel pump/relay upgrade wiring

  1. #1
    turbo addict Turbo Mopar Contributor iTurbo's Avatar
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    Fuel pump/relay upgrade wiring

    I am looking into upgrading the fuel pump wiring for a Spirit R/T. I have a sneaking suspicion that the lean condition that this car is experiencing at WOT is due to the tiny stock fuel pump wiring. I would like to use an auxiliary relay and use the stock fuel pump wiring to activate the relay, while using upgraded wiring (8 gauge?) to power the fuel pump right off the alternator + terminal.

    I've done this before on my S/C Regal GS with a kit from Racetronix. They don't have anything available for turbo Mopars though. Is a kit available out there anywhere that will have a plug-and-play harness (or at least the fuel pump sending unit plug)??

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    Supporting Member II Turbo Mopar Contributor DOHCRT's Avatar
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    Re: Fuel pump/relay upgrade wiring

    Jeremy, I don't know if a plug n play kit. I just did this on my R/T and picked up 1.1 volts @ the pump @ idle. I ran a new 10 ga power wire from the fuel pump relay back to the pump using the factory connectors and a 10 ga ground from the pump connector to the body ground in the trunk (I used the same ground point as the factory). At the relay I ran 10 ga to the relay from the battery and modified the 2 terminals in the relay socket to accept 10 ga wire. TAkes a bit of time, but looks factory, eliminates the need for a seperate relay in the rear of the car and works perfect.


    Vic in Phoenix
    dohcrt@cox.net

    91 Spirit R/T x4
    92 Spirit R/T x2
    89 CSX
    88 CSX-TIII
    84 Rampage TII
    97 Ram (Buzzin Half Dozen)
    69 Dart GT 'Vert

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    boostaholic Turbo Mopar Contributor
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    Re: Fuel pump/relay upgrade wiring

    Quote Originally Posted by iTurbo View Post
    I am looking into upgrading the fuel pump wiring for a Spirit R/T. I have a sneaking suspicion that the lean condition that this car is experiencing at WOT is due to the tiny stock fuel pump wiring. I would like to use an auxiliary relay and use the stock fuel pump wiring to activate the relay, while using upgraded wiring (8 gauge?) to power the fuel pump right off the alternator + terminal.

    I've done this before on my S/C Regal GS with a kit from Racetronix. They don't have anything available for turbo Mopars though. Is a kit available out there anywhere that will have a plug-and-play harness (or at least the fuel pump sending unit plug)??
    Wow man, I would certainly hope you don't need 8 gauge. According to this web site: http://www.powerstream.com/Wire_Size.htm in chassis wiring, 8 gauge is good for 73 amps. If you have a pump pulling that, you have issues!!!!

    I agree with DOHCRT, 10 gauge should be plenty for anything you plan on running.

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    Supporting Member Turbo Mopar Contributor supercrackerbox's Avatar
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    Re: Fuel pump/relay upgrade wiring

    The other thing you may want to consider is the tiny outlet of the factory pump itself. I don't remember the details specifically, but when Ray upgraded the pump in his R/T, he discovered the setup has a tiny, tiny outlet compared to the older style pumps. > 1/4" IIRC. When the time comes to upgrade the pump, you may want to consider switching to an older style tank and pump.

    As to the wiring, I'm always all for upgrading. I think Chrysler should have stepped up a gauge or two on many circuits in these cars, and the wiring certainly hasn't gotten any better with age.

  5. #5
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    Re: Fuel pump/relay upgrade wiring

    I cut the stock wiring at the tank and use that to actuate a relay. I run the hot side right off the alternaror and run a dedicated ground back to the engine block. You can buy a plug for the relay but I use individual terminals that I crimp, solder and heat shrink the plugs are just crimped and the wire is small.

  6. #6
    turbo addict Turbo Mopar Contributor iTurbo's Avatar
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    Re: Fuel pump/relay upgrade wiring

    Quote Originally Posted by supercrackerbox View Post
    The other thing you may want to consider is the tiny outlet of the factory pump itself. I don't remember the details specifically, but when Ray upgraded the pump in his R/T, he discovered the setup has a tiny, tiny outlet compared to the older style pumps. > 1/4" IIRC. When the time comes to upgrade the pump, you may want to consider switching to an older style tank and pump.

    As to the wiring, I'm always all for upgrading. I think Chrysler should have stepped up a gauge or two on many circuits in these cars, and the wiring certainly hasn't gotten any better with age.
    Got that covered Adam! I noticed that too when I had rerun all the fuel lines on the car with 3/8" hard tube. I had a local radiator shop braze in 3/8" on both send and return in place of the stock tubes on the sending unit (ALL the way into the tank), and then AN flared the ends to connect SS braided hose.

    Thanks for all the info everyone. Wallace, that is how I was thinking about doing it and that is the way the Racetronix kit I have on the Regal GS works. I sure hope I can eliminate the all the stock wiring and plug, but it might be difficult because the way the terminals are on the sending unit.

    If it turns out that won't work or is crazy difficult, I'll probably do it like Vic did with 10ga wiring. That is awesome that you gained 1.1v at the pump. That oughta help WOT fueling on this car I would think.

  7. #7
    Supporting Member II Turbo Mopar Contributor DOHCRT's Avatar
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    Re: Fuel pump/relay upgrade wiring

    I didn't want any additional relay's hanging aorund the car, it's busy enough under the hood. Just one more component to add to the troubleshooting tree when something stops working. I just disassembled the relay socket and added the 10ga wires going into and out of the relay.


    Vic in Phoenix
    dohcrt@cox.net

    91 Spirit R/T x4
    92 Spirit R/T x2
    89 CSX
    88 CSX-TIII
    84 Rampage TII
    97 Ram (Buzzin Half Dozen)
    69 Dart GT 'Vert

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    turbo addict Turbo Mopar Contributor iTurbo's Avatar
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    Re: Fuel pump/relay upgrade wiring

    Did some checking with the digital voltmeter today on this '91 Spirit R/T.

    With the car idling..

    Voltage at alternator: 14.65v
    Voltage at battery (mounted in trunk, with 2ga cabling for +/-): 14.35v
    Voltage at fuel pump connector:12.7v

    Houston, we have a problem....

  9. #9
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fuel pump/relay upgrade wiring

    That is a problem for sure. If you have the battery in the trunk then a relay makes a lot of sense to me.

  10. #10
    turbo addict Turbo Mopar Contributor iTurbo's Avatar
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    Re: Fuel pump/relay upgrade wiring

    Quote Originally Posted by cordes View Post
    That is a problem for sure. If you have the battery in the trunk then a relay makes a lot of sense to me.
    My gut tells me this is at least part of the problem with regards to the lean condition at WOT. Last time I rode in the car we were seeing upwards of 13.xx+ A/F ratio at WOT with 20 psi boost. I would love to see this # back down into the 11.xx A/F obviously. I will report back when it is complete. For now, the car is in a garage and awaiting upgrades and nothing has broken.

    I must say I am impressed with the stock (forged) TIII pistons for what they have endured.

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    Hybrid booster
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    Re: Fuel pump/relay upgrade wiring

    The SRT4 guys claim that they have to pull fuel in the upper RPM's and gain a few MPG's after doing the relay setups. I'd imagine that we would have similar results, especially considering our wiring is 20+ years old.

    This is something on the list for my car for sure.

  12. #12
    Garrett booster
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    Re: Fuel pump/relay upgrade wiring

    For my srt4 i used 10g with the stock relays -- gained ~2v at the pump -- and yes, lots of srt4 guys use a rewire/relay kit..

    Quote Originally Posted by Tbird232ci View Post
    The SRT4 guys claim that they have to pull fuel in the upper RPM's and gain a few MPG's after doing the relay setups. I'd imagine that we would have similar results, especially considering our wiring is 20+ years old.

    This is something on the list for my car for sure.

  13. #13
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    Re: Fuel pump/relay upgrade wiring

    Quote Originally Posted by Tbird232ci View Post
    The SRT4 guys claim that they have to pull fuel in the upper RPM's and gain a few MPG's after doing the relay setups. I'd imagine that we would have similar results, especially considering our wiring is 20+ years old.

    This is something on the list for my car for sure.
    A.J. gain 1.5V.

    http://www.turbo-mopar.com/forums/sh...cal&highlight=

  14. #14
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fuel pump/relay upgrade wiring

    Quote Originally Posted by Tbird232ci View Post
    The SRT4 guys claim that they have to pull fuel in the upper RPM's and gain a few MPG's after doing the relay setups. I'd imagine that we would have similar results, especially considering our wiring is 20+ years old.

    This is something on the list for my car for sure.
    Don't the stock SRT4s vary the power to the pump or some such rather than running a regulator and return like we do? I don't think the added pump capability should effect anything unless the regulator isn't up to the task.

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    turbo addict Turbo Mopar Contributor iTurbo's Avatar
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    Re: Fuel pump/relay upgrade wiring

    Quote Originally Posted by tryingbe View Post
    After looking into this '91 Spirit R/T we are working on, I am not surprised. It looks like we stand to gain nearly 2v at the pump with better wiring.

    Still weighing my options as far as what to do... I noticed that AJ had the older style 'triangular' fuel pump plug. The Spirit R/T we are working on has the newer style hanger with a GM Weatherpack style plug. The plug is actually removeable from the sender flange, so hopefully we can figure something out like A.J. did without having to go back down to 16ga just before the pump. Hell I've already had 3/8" tubes brazed into the damn thing, I'll figure it out.

  16. #16
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    Re: Fuel pump/relay upgrade wiring

    For my GLH, I'm just gonna combine both intake pump and inline pump wiring to supply power to the new 10 gauge hanger wiring. Should make the job a lot easier.

  17. #17
    turbo addict Turbo Mopar Contributor iTurbo's Avatar
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    Re: Fuel pump/relay upgrade wiring

    Quote Originally Posted by tryingbe View Post
    For my GLH, I'm just gonna combine both intake pump and inline pump wiring to supply power to the new 10 gauge hanger wiring. Should make the job a lot easier.
    Just curious, does your GLH still use the stock 2-pump setup that the cars originally came with? Or have you upgraded?

  18. #18
    turbo addict
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    Re: Fuel pump/relay upgrade wiring

    I upgraded to an intank pump with a DW200, but left the inline pump wiring intact. Going to put in a DW300 and use both the intake/inline wiring to power it, hanger wiring will be upgraded to 10 gauge. That would save me the trouble of run the new wiring to the hanger, relay and other stuff.

  19. #19
    turbo addict Turbo Mopar Contributor iTurbo's Avatar
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    Re: Fuel pump/relay upgrade wiring

    Ah, I see. I will have to look under my own GLH Turbo to see if that original wiring still exists if/when I do this upgrade on that car. Thanks for the idea.

  20. #20
    Hybrid booster
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    Re: Fuel pump/relay upgrade wiring

    Quote Originally Posted by cordes View Post
    Don't the stock SRT4s vary the power to the pump or some such rather than running a regulator and return like we do? I don't think the added pump capability should effect anything unless the regulator isn't up to the task.
    The SRT4 has a regulator in the top of the fuel pump hanger. It's a specific rate regulator, set at 58psi. A lot of those guys will use an aftermarket regulator and set up a return line when they start putting down some power and need more fuel.

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