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Author Topic: New Fuel Pump Noise, Fluctuating Gas Gauge  (Read 804 times)

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Offline Jolly Green Giant

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New Fuel Pump Noise, Fluctuating Gas Gauge
« on: January 30, 2013, 03:52:38 PM »
Ok guys, now I'm stumped. New Bosch FP installed last Thurs--old one (OE) was whirring louder than engine while rolling down the road like a Waring blender, pulsating in time to the turn signal, and dipping in pitch when I applied brakes--IOW voltage sensitive.  Gas gauge was fluctuating like FP float was possessed by demons.  When I picked-up the truck I went into the rear and listened intently--zero whir noise.  Thought I licked it.

My gas gauge still fluctuates, drifts, etc., but after 90 miles on new FP I'm now hearing it whirring ever so slightly at idle (not as loud as before) again, pulsating in time to turn signal and dipping when I apply the brakes.  My RC is a base model, with just black rubber in the back and the rear seat has been removed.  So maybe there's nothing to muffle normal FP noise?  For most of this week driving to work I could only hear the brief FP "buzzt" at turning on, and a short "buzzt" immediately after the ignition is turned off. But why would a brand new FP float still act possessed at the gas gauge?  Does normal healthy FP noise pulse as the turn signal blinks, and dip when brake  lights come on?  Should I go back to the shop, or wait for it too get louder?
1992 RC, 5.9 LE, base, Virginia Fish & Game Warden "green"

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #1 on: January 30, 2013, 05:16:27 PM »
you still have a power feed issue like l said to check before / if you hafta your gonna haqfta run a new wire from the ASD relay right to the pump / your getting back feed from something
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Offline Jolly Green Giant

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #2 on: January 30, 2013, 06:14:40 PM »
"ASD"?  You went right over my head.  The new pump ain't getting damaged I hope?
1992 RC, 5.9 LE, base, Virginia Fish & Game Warden "green"

Offline cattech

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #3 on: January 30, 2013, 06:42:28 PM »
check all your grounds and clean them

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Offline 88raminator

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #4 on: January 30, 2013, 07:01:20 PM »
ASD is automatic shut down relay IIRC. The fuel pump on my RC also changes tone/pitch with the signal lights. Now you got me thinking if it's a ground issue or back feed
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Offline Jolly Green Giant

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #5 on: January 30, 2013, 07:57:37 PM »
ASD--Roger that. Thanks

Grounds--Roger that. Thanks

Paid my shop good $ for new Bosch FP.  They said they checked relevant relay, grounds, voltage....ugh-huh.

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1992 RC, 5.9 LE, base, Virginia Fish & Game Warden "green"

Offline Jolly Green Giant

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #6 on: February 1, 2013, 02:59:45 PM »
JGG is headed back to the shop Monday.  I searched RCC "fuel pumps", "fuel gauge", "sending unit" etc. and edited together about three pages of relevant sage wisdom text for them (mostly on fixing bad ground).  With brand new Bosch FP in there, a leaking float and bad sending unit should be ruled out as affecting my drifting gas gauge. I'll have them chase grounding issues, do the test to see if it pegs out at "F", check ohms, etc. If anybody can offer a nice short, presice, technical instruction for me to pass on to the technician so I don't just give him three pages of RCC search results to decipher, I'd be much obliged.  I offered to loan him my '92 FSM, but he has AllData on-line, and declined. I guess he has relevant FP wiring diagrams, color codes, etc.

On just the FP noise, let me rephrase my original questions:

On a base model w/ only rubber mat, and no back seat in it, should you be able to hear the FP whirring (quietly) at idle at all?
If soft audible noise is OK, should this noise fluctuate in time with turn signals blinking or drop when brakes are applied?
Is driving with this FP ground/voltage issue going to damage this brand new (not cheap), FP?
Am I being an obsessive newb? Be honest ;)

After new FP went in, and I filled it up, all was quiet back there for a day or two, but as the tank's gotten emptier, I could hear FP again (faintly, not loud like old one), louder once ytruck's warmed up, or it shot up to 75 degrees Wed. Of course with gauge acting like it's possessed, who knows.  I think there's about half a tank in there, 'cause it's reading around 1/4.  Last time it only took 14 gallons at that point.  Bottom of tank skid plate is level with top of rear axle, so it's gotta be the deep 34 gallon one.   
1992 RC, 5.9 LE, base, Virginia Fish & Game Warden "green"

Offline Ruderunner

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #7 on: February 1, 2013, 03:30:14 PM »
The change in fp noise with the turn siginals indicates a power or ground problem.  Low voltage can damage the pump by causing it to run hotter.

Find your electrical problem.

Yes the fuel dampens the noise but I still don't think you should be able to hear it at 1/2 tank.

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #8 on: February 1, 2013, 03:50:16 PM »
fuel pump should happily buzz away at a low hum  / louder with empty tank / and yes the voltage drop out will kill it fast
put your truck info HERE
MOPAR TO YA! AARON HOWORD TOWNSEND / SLANTEDMIND---GOD BLESSDODGEBOYS FSM STORE
ramchargercentral@hotmail.com
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Offline Jolly Green Giant

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #9 on: February 1, 2013, 06:48:26 PM »
Thanks guys, your support is much appreciated.  Maybe the good that will come from this thread in posterity is some other guy will read how critical proper voltage/good ground is to his FP.  Shop saved my OE MOPAR FP, which I'll save in case it can be rebuilt for a spare.  I'll stick to my guns Monday's hope they can pinpoint and fix it right.  Shop has a 2(!) year warranty on their work, so it's their problem if this FP fries early. I just want to be d.o.n.e. worrying fuel system issues and move on to funner crap like H2o leaks, floor rust, and little crap I mostly can do myself.  Taking fuel tank in/out 4 times in a row can't be too good for it. Of course I don't want to get stranded with a dead FP up some remote fire road in the Shenandoah Valley camping either, because of a bad ground.

Hoped she was home until spring this time...  Think good thoughts Monday, I'm taking the weekend off from RC restoration frustration.  Hope the window "felties" and weather stipping is an easy job.  Looks straight foward in the FSM.
1992 RC, 5.9 LE, base, Virginia Fish & Game Warden "green"

Offline Jolly Green Giant

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #10 on: February 19, 2013, 04:04:11 PM »
Picking JGG up tonight after work.  Grounds/voltage to FP all test good shop says.  Only wiring issue found was a purple wire near the FP that had been spliced, twisted back together and wrapped with electrical tape (properly crimped now).  No idea what the purple wire is, any of you?  Could that have been at fault? Apparently my '92 FP does not share ground with rear lights/wiring harness.  No need to run new wiring from shutoff relay Dean, "it's fine" now I'm told. I'll fill her up again and see if the gas gauge acts any more sober.

Two weeks is a long time to be without my RC, but I got the "no hurry" discount--zero charge for installing my window felties, lubing the window mechanisms, and busting loose all the frozen floor trim screws and some other little crap.

Now, THE INTERIOR IS ALL MINE! *Bwahahaha* 8)
1992 RC, 5.9 LE, base, Virginia Fish & Game Warden "green"

Offline Jolly Green Giant

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #11 on: February 20, 2013, 06:55:36 AM »
Update--

Lots of rain and road noise on drive homelast night, so will have to wait to see if purple wire fix and new in-line fuel filter silenced FP. But, progress...  gas gauge was sitting steady though, a little below 1/4 tank.  Filled her up until gas spilled out the filler.  Took 17.9 gallons.  After hitting a few good bumps exiting service station, gas gauge needle slowly moved to a hair above the "F" and sat there rock steady all the way home (except on hard left turn some downward motion).  So, if it behaves now I think I have this FP/gauge crap licked, and on mine 1/4 tank is still around 1/2 full (34 gal. tank)  ;D

Got OEM FP back too. Tech had to re-use the "roll-over valve" (WTF that is?) out of it he said, so it's now junk unless somebody needs the float/sending unit.
1992 RC, 5.9 LE, base, Virginia Fish & Game Warden "green"

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #12 on: February 20, 2013, 12:56:27 PM »
its not junk just because the roll over valve is gone unless the moron ruined it removing it
put your truck info HERE
MOPAR TO YA! AARON HOWORD TOWNSEND / SLANTEDMIND---GOD BLESSDODGEBOYS FSM STORE
ramchargercentral@hotmail.com
DO NOT use the site IM,s to contact me  l have them turned OFF

Offline Jolly Green Giant

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #13 on: February 20, 2013, 03:48:15 PM »
The screws that holds the slider brackets that hold top to the bottom are missing all but one, and it looks kinda empty inside.  What I know about FPs would fill a walnut shell though.

Any idea what the "purple" wire was near the FP he found badly spliced and fixed?  Everything seems better now.  Could that have been voltage/ground issue?
1992 RC, 5.9 LE, base, Virginia Fish & Game Warden "green"

Offline Furyschild

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #14 on: February 20, 2013, 11:30:49 PM »
did you replace the whole fuel module or just the pump?
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Offline Jolly Green Giant

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #15 on: February 21, 2013, 06:30:51 AM »
Whole thing with a Bosch.
1992 RC, 5.9 LE, base, Virginia Fish & Game Warden "green"

Offline Furyschild

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #16 on: February 21, 2013, 08:54:16 AM »
Wow , I just did same project with the Carter module and it went flawless , other than lack of space to get at all the lines ,guage works perfect ,cannot even hear it run ,and its hi volume pump.cost $148
« Last Edit: February 21, 2013, 08:55:49 AM by Furyschild »
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Offline Jolly Green Giant

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #17 on: February 22, 2013, 07:33:17 AM »
Sitrep/Update--

Whatever the "purple" wire near FP was that tech fixed (loose twisted splice) has changed FP issue, but not eliminated.  Gas gauge needle staying more steady now, but still reads wrong:  "F"=full; 1/2=2/3rds full; 1/4=1/2 full. The FP buzz is now faintly audible only when stopped, but still dips when brake lights go on, or oscillates in time with turn signal or hazard flashers.  Noticed yesterday the needle on my dash amp gauge moves a hair, too, in time with blinkers.  Zat a concern?

When R & Ring the fuel tank recently (3 times!), the tail lights went dead.  Tech found corroded wiring and fixed it so it works.  Trusted guru (Dean) says go after my tail lighting wiring next to solve the problem, but FP might buzz away like that for years without pooping-out.

On the upside, topped up the tank yesterday, 11.5 gals. for 158 miles mostly around town.  13.7 mpg with a TBI 360 with 117k on the odo--I'm lovin' it.  Will I get even more mpgs with alloy rims instead of these old steel ones?  Gas prices have gone crazy  :)
1992 RC, 5.9 LE, base, Virginia Fish & Game Warden "green"

Offline Jolly Green Giant

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Re: New Fuel Pump Noise, Fluctuating Gas Gauge
« Reply #18 on: February 27, 2013, 09:00:16 AM »
Gonna pick it up tomorrow.  Regular mechanic found:  bad battery clamps, and ground strap at engine block busted.  Let's see if this licks the buzzing FP/drifting gas gauge.
1992 RC, 5.9 LE, base, Virginia Fish & Game Warden "green"