Jeep Renix Fuel Pump...little simple advise.

John Fuller

John Fuller

XJ Fanatic!!
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Jan 3, 2015
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Boone NC
i'm lost or i've lost my brain..one or the other or both! LOL
fuel pump went out driving jeep yesterday (wanted to give good test drive for next weekend's trip) and fuel pump went. kinda new it was weak but anyways, got new one, put it in it works BUT (Renix electrical guys please chime in) now it doesn't stop priming it just keeps on running. it starts right up, runs good, holds right at 38psi and doesn't bleed any when off.
Question: why would all of sudden putting in new pump and won't stop priming/running? what i mean by priming is the noise pumps make at first KOEO then stops and when engine starts the pump keeps running but not as loud as they are when priming (i guess not full voltage). ALSO WEIRD...unplugging the Fuel Pump Ballast Resistor doesn't do anything now (before pump doesn't run or prime unless it's plugged in) WTF :wtf: so please any help.

FINAL NOTE: is there any drawback to just rewiring the fuel pump to a switch or to run with ignition on constantly...i've read many doing it but some say burns them up faster others say it works fine just louder so no clear decision there. thank u very much guys. even owning so many of these, first time ever running into this issue....Dam electricals!!!
 
so before we get too far i just wanna make sure i understand the electronics of fuel pumps since electronics is my weakness: When pump is primed on cars it's "louder" because it is given full power and then once the engine is running, the voltage directed to the pump by either ecm, relay, some module,etc...cuts the voltage down and that's why they aren't the same noise as when priming?? i know the sound of the car muffles some of the sound but considering how loud lound they are when priming, you would be able to still hear it the similar amount if they were the same?
a note for mine: the "Normal" XJ pumps are loud when priming and about half the loudness when running even with a real quiet exhaust. Right now mine is just as loud from the time you turn the key and on and on so that sound "loudness" it makes when priming it just keeps going and going like the energizer bunny LOL.
Bhudgins said:
I put a 2jzget in a lexus one time and ran the fuel pump off a relay and it worked just fine
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not a bad idea but just curious:: would this be any different than what it's doing now? another words if wiring up like your mentioning would still have the result of "loudness" it has now, i guess it wouldn't hurt to keep it like it is. I'm just afraid to "BURN UP" this new pump if that would even happen???thank you
 
Bhudgins said:
I don't know about the loudness because that car had I big fuel system that was loud no matter what
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LOL, yeah that would make sense on that one. in the past 15years i've always bought Airtex pump assemblies and never had an issue...usually the Airtex ones are little louder than factory but NOT LIKE THIS lol. it's not the loudness that bothers me at all...it just seems something is wrong since it makes that priming sound constantly. (hoping Jody chimes in...he seems to know more about jeeps and even the Renix ones)
 
So is the question "Why is my new fuel pump louder than my old one?"
To answer one of your questions, most electric fuel pumps get 12v key on, cranking and running. Renix's are a bastard child in the fact they switch from 12 to 6v.
It sounds like there is an electrical issue but to be honest, you arent making any sense.
You can always run it through a relay with 12v and stop throwing parts at it.
 
Jody Treadway said:
It sounds like there is an electrical issue but to be honest, you arent making any sense.
You can always run it through a relay with 12v and stop throwing parts at it.
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i figured i wasn't: try again. You know how when u turn the key, pump (on jeeps especially) is plenty loud enough when priming then stops..once running you can usually on XJs hear it hum. Well my old pump died (not abnormal being original and 20+yrs old) and knew it would soon but when i put new one in, immediately primes but now doesn't stop the "priming noise"...so after u start it you can hear it loud like it is when priming instead of just hum and it's louder than normal (i know Airtex pumps are usually louder than stock) but this is like stupid loud like too much voltage going to it or something.
2. electrical problem: YES. as i start to fiddle with it, unplugging Ballast resistor before would cut power to fuel pump (like it should), now it doens't keeps running. i'm just afraid to burn up the pump to let it run for too long. (i'm only replacing IGN switch cause its 11.00 and has the normal one wire that's burned like they all usually are). all my years of wrenching i've just never heard a pump keep on priming and priming...if i leave the key on and not start it..it just keeps priming and priming and sound is pretty darn loud.
 
in the morning...for temporary use I was going to straight wire the pump with new ground and power just to see if the "noise" is normal...which would verify that there is way too much voltage being given to it...but why with just changing pump is the weird part. The noise doesn't bother me except it's just "that loud" that you know something is not right type of loud...i'm sorry I hope I'm making sense this time
 
Jody Treadway said:
You can always run it through a relay with 12v and stop throwing parts at it
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so the pump will not burn up just wiring straight through 12v supply even though the factory set it up to run at 6/7 after cranked up?
 
Jody Treadway said:
How much voltage is.present at the pump at key on and while running
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i will check this in the am. i know it's 12 but don't know the axact. i was too busy freaking out over the "electrical" scare of the noise and then the ballast resistor not cutting power when unplugged etc etc. but will in the am. just trying to get ideas to try in the morning. i like to start the day fresh with ideas: so far 1. new ign switch install, 2. check exact voltage at pump when priming, 3. start cleaning grounds, 4. test purpose straight feed pump to see if operates at normal audible levels, 5. remain calm if none of the above work, 6. pour gasoline and light a match on all the electricals and convert to carb! OK THE LAST 2 are jokes cause been one of those days and electricals just really really get under my skin. mechanical doesn't bother me but wiring and some ADD has never worked well together lol. thanks u sir, very much.
 
I LOVE the Renix jeep for the ruggedness of the 4.0 but hate them for their electrical BS!!! and after owning so darn many, they still tend to give me different problems with each one i get...except now this is the final one for me personally since i'm actually keeping it...and i'm only a computer/ignition module/and starter relay away from ALL STUFF being new...i guess after those start with the harness lol
 
Jody Treadway said:
Won't hurt it whatsoever.
How much voltage is.present at the pump at key on and while running?
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uhh oh. first of all: voltage at pump when key on is 10.9 and while running 13.16
Jody bear with me...while replacing ign switch, found fused added circuit that guess what...sending power to the pump so with B+ latch relay and Fuel pump relay, the fuel pump still powers and jeep runs WTF WTF...how can jeep run without B+latch relay. so i unravelved some of the harness where that wire runs to under hood by the batt, he (some previous electrical mechanic???) spliced into a orange with black stripe wire which i seems to be same color as fuel pump ballast resistor wires...so what now. i guess first question is is the voltage readings ok with pump priming and then running? but with old pump did it stop priming like regular until started but now keeps on. i have computer in the shop so i can keep up with this.
(BTW, i will do my best to compensate you for your time next weekend cause i know your time and expertise is worth money and is much appreciated).
 
OMG OMG...I FIXED IT. sometimes i'm smarter with this little voltmeter than i give myself credit.
i decided to start probing EVERTHING including what the other person had done and another fused circuit that he added in sure enough no voltage across fuse...followed wires and it powers the relays...found the butt-connector was loose and when moving it test light went on but then off when moved around...took apart sure enough not crimped good enough. now the pump primes "QUIETLY" then runs with a hum like normal and voltage to the pump is now right at 8.2 when running which from my understanding is proper with these renix jeeps. OMG, God is Good. and thank you Jody and everyone else who has helped guide me in the right directions. have a blessed weekend. See you all next weekend.
 
hey so i put pressure gauge on it again and even though it's only got 6.5volts on prime and 8.1 when running, it primes right up to 38 and holds steady. now when i shut off to test leak down...for 25minutes now been holding 41psi so i guess system is all good??? isn't that 6.5volts for prime a little low even for the Renix setup?
 
Is it an air tex fuel pump? , me and a old roommate had this problem it's just a badly made pump and was louder then a train . One or other of use ended up spending more coin ( plus rebate from the first pump) got better brand ( I'll have to find box on parts shelf can't remember atm ) and fixed problem , they worked fine just were louder then my exhuast.
 
CThurmond said:
Is it an air tex fuel pump? , me and a old roommate had this problem it's just a badly made pump and was louder then a train . One or other of use ended up spending more coin ( plus rebate from the first pump) got better brand ( I'll have to find box on parts shelf can't remember atm ) and fixed problem , they worked fine just were louder then my exhuast.
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i've always heard this but with most Airtex pump i've installed, they are little louder but not as loud as a lot say. the ones that are i just get a warranty for new one, even 5 years later i still get em free (they are lifetime warranty after all). only on 97+ jeeps do i get the better ones cause dropping the tank is required so that would suck to have to do it twice lol but the cherokee are so quick to change doesn't bother me to swap a bad one out.
 
John Fuller said:
isn't that 6.5volts for prime a little low even for the Renix setup?
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anyone know if this is normal for these...i would think it should be 12 but still pumps plenty of fuel. let it run for about 40min today and drove around a bit and works great so far so i guess it's good...
 
just thought i would share some Renix wiring info for some who have the 87-90 jeeps: i kept fooling with my fuel pump wiring cause i just wasn't satisfied with how the new pump sounded after i fixed it and wasn't fond of the wiring that some other before me tech had done. SO...i took ALL grounds off, cleaned to bare metal/scrape and reinstalled. 2> cut power wire to starter and to starter relay (many frays and corrrosion in wires) and recrimped new poles with new terminal, 3> added another 6ga ground wire from negative post to frame by radiator support after scraping that to bare metal, 4. spliced in new ground to fuel pump area, spliced in new ground to TPS sensors, and spliced in new ground to computer harness under DS Dash....AND WOW. now the fuel pump sounds perfect, works perfect, voltage is perfect and best of all....i had the wires disconnected that he spliced in for fuel pump circuit and didn't know it until after it was running and later i checked. i've always known ground wires and such are problematic on these Renix jeeps but this is the first out of numerous Renix Jeeps that i've gone through this thorough and it paid off. So just want to encourage anyone with Renix jeeps to CLEAN CLEAN ALL ground, ADD one more at least, and double check your connections on battery terminals, starter relay expecially cause i found the 6ga wire going to starter relay from battery had about 7or8 strands broken and i would bet that's why he had to tap into the wiring. just thought i would share my experiences and hope it helps someone else out. Enjoy the week. See you guys this weekednd!!!
 
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