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Fuel pump replacement 93 cut conv


gr_elvis
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Can you change fuel pump without removing gas tank completely ? I'm doing this in my driveway and have the rear wheels on ramps . Is there a shortcut to changing fuel pump? Please help its beautiful weather and I want to get my baby back on the road. Thanks

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Can you change fuel pump without removing gas tank completely ? I'm doing this in my driveway and have the rear wheels on ramps . Is there a shortcut to changing fuel pump? Please help its beautiful weather and I want to get my baby back on the road. Thanks

Not realistically.  Drop the tank, change the pump, strainer, harness, and verify the pulse dampener.  It's also the perfect time for a new fuel filter. 

 

I don't get it.  Dropping the tank is NOT HARD, at least on my '92 Lumina.  Why are you so obsessed with a shortcut?

 

Don't forget to do voltage, amperage, and pressure testing before and after.  Seems like about a third of "fuel pump" problems are really problems with the wire harness in the engine compartment, or corroded ground wires/connections.  My Luminas have under-sized wires and therefore designed-in voltage drop of over one volt on the power side of the pump, and about a volt on the ground side.  Therefore the pump is actually running on two volts less than system voltage; and that's a shame.  GM saved a nickle on wire by not adhering to industry standards for wire gauge versus wire length and amperage draw--they used 16 gauge wire when they needed 12 gauge.

 

If the pump you buy doesn't come with an in-tank wire harness kit, the in-tank wire harness is available separately for about twenty dollars.  In-tank wire harness corrosion is ultra-common.

Lumina_Fuel_Pump_24.JPG

 

New wire compared to original wire.  The new harness is "universal fit", so the actual wires are a bit longer than the originals--but they have the correct connectors on them.

Lumina_Fuel_Pump_25.JPG

 

Don't forget to CLEAN OUT THE TANK because grit in the tank is the number-one cause of replacement fuel pump failures.

 

Lumina_Fuel_Pump_38.JPG

 

 

 

I mark the outside of the tank with date, mileage, and parts replaced.

Lumina_Fuel_Pump_46.jpg

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I believe it was pointed out in another thread that the best way to do this is to drop the tank.  There are features of that vehicle that don't really allow you to take shortcuts.  As much as it sucks to drop the tank it seems like that is your best option.

Good luck!

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Because I'm a big guy and I can't get into all the nooks and crannies to get the tank out in my driveway. I tried now I'm cutting a access hole ...hopefully ....

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This is funny.

You will ruin the car cutting holes trying to find the correct spot above the sending unit bung.

If you manage to cut a large hole in the correct spot you probably won’t be able to remove the bung or the fuel lines.

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Horse...Water...Not drinking...must-try-harder...

 

 

 

 

 

I had a fuel pump failure in my '93 Lumina, five states away from home, at ~150K miles.  I limped into the sixth state, and paid a shop to replace the pump.  I think it came to $550, parts and labor.  I'm pretty sure the shop understood that I was from out-of-town, desperate, and stranded.  They did their best to extract the maximum amount from my wallet.

 

When I got home, I refused to be stranded by a failed pump in my other Lumina.  I ripped the pump/strainer/harness out of my 120K mile '92 in my driveway, with the ass-end of the car on jack stands.  If I can do it in a long afternoon, so can you.  I spent < $100.  (This doesn't include the time I spent screwing around with the wire harness in the engine compartment of both vehicles, in utter dis-belief of GM's cost-cutting.  Their use of undersized wire makes the fuel pump electrical system VERY sensitive to corroded connections or any other deterioration that would reduce voltage/amperage to the fuel pump.  Every section of wire that I tested showed a couple of tenths-of-an-volt of voltage drop, totaling about two and a half volts "missing" at the pump.  There was nothing to "fix" other than to rip the entire harness out and start over--which I did not do.  The OEM 16-gauge wire is still there.)

 

Maybe you need to buy a decent set of jack stands, instead of the ramps currently used.

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So if the factory harness is too small for the electrical load does that mean the fuel pump is designed to run on that dropped voltage or does that mean the factory fuel pump is straining to run with that voltage drop?

 

Would replacing the harness with the correct gauge wire cause issues with a replacement factory ACDelco or Delphi pump designed to operate at a lower voltage?

 

I havent replaced my pump in my 94 CS yet and I would have never known about that issue with the harness nor would I have known to check. It will be interesting to see if GM ever corrected that issue and if so during what years.

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Don't do it!  I think it will end in EPIC FAIL.

 

There are no shortcuts!

 

The fuel-pump module has fixed metal pipes coming off of it.  That means you'd have to cut a REALLY BIG HOLE to remove the fuel lines from the pump module in order to lift the pump module out of a hole.  Also, the module is at the high part of the tank which is under the trunk floor but really close to framework behind the seat.  The metal pipes run forward partially below that framework.  So you'd have to A) cut a really BIG hole (approx 1sq ft, bigger on the older models without quick disconnects because their pipes extend further forward) and B ) Yank the back seat and cut the hole through all that framework behind the seat.  The grommet/passthru thing with the wiring in the trunk is quite a bit behind where you would have to cut a hole.

 

It would be much easier just to do it right and drop the tank.  If that's too big of a job for you, pay it done or get a different car.

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Yeah.....convertibles have extra bracing above the sending unit which is in addition to all the other above mentioned reasons not to cut a hole.

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I'm trying to do it right but I have a half tank of fuel in that I can't get out, and having a devil of a time getting the tank loose . I have the back on ramps and the front on jack stands in my driveway. I was just asking if anyone here knew a better way . And if my first question would have been answered with the location information , that wouldn't even be an issue . That's what I originally wanted to know. I only thought of the access hole idea because I had done it on 2 other cars and it worked like a charm but they weren't convertibles. 1 was a cavalier and the other was a topaz , totally different cars. That's why I came here specifically I figured someone here would know exactly where the pump is under the floor. I just want my car back on the road. I appreciate the information and understand the disapproval and even the humor. I hope to continue to be part of site and make even make some friends. I'm hoping to drop the tank tomorrow but it does still have the gas in it. I could not get it out. Wish me luck . If you've seen the pic of my car you know I'm trying make her beautiful. Thanks for reading this and I hope you now understand why I kept asking for alternatives .

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If the pump still has any life in it, you can disconnect the fuel filter line and short the fuel pump prime connector to the aux batt terminal (that loose wire near the aux batt terminal).  That should run the pump and pump the fuel out.  If it's completely dead, you can use a siphon through the disconnected fuel filler or vent line (can't go through the filler neck due to check ball).  I keep a spare junk fuel pump that powers up that I use to pump fuel out of a non-empty tank with a dead pump.

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I undo the big rubber hoses to the fill tube and siphon from there to drain the tank.

 

I believe it was pointed out in another thread that the best way to do this is to drop the tank.  There are features of that vehicle that don't really allow you to take shortcuts.  As much as it sucks to drop the tank it seems like that is your best option.

Good luck!

 

Yeah, we LITERALLY just did this: http://www.w-body.com/topic/55055-where-do-i-cut/

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So if the factory harness is too small for the electrical load does that mean the fuel pump is designed to run on that dropped voltage or does that mean the factory fuel pump is straining to run with that voltage drop?

 

Would replacing the harness with the correct gauge wire cause issues with a replacement factory ACDelco or Delphi pump designed to operate at a lower voltage?

 

I havent replaced my pump in my 94 CS yet and I would have never known about that issue with the harness nor would I have known to check. It will be interesting to see if GM ever corrected that issue and if so during what years.

 

I believe that the pump would work better if the wire harness wasn't undersized.  I don't think it was specially-engineered to operate on low voltage.  I could be wrong.

 

Voltage-drop testing is a pain in the ass when it comes to fuel pumps.  I needed 15 or 20 feet of 12-gauge wire from battery +, and then from battery - posts back to the fuel pump area to determine the level of voltage drop in the + and the - side of the circuit, respectively.  Other than that, it's standard voltage-drop testing.

 

I just hate replacing an electric fuel pump without testing the voltage supply, the ground, and the amperage draw of the fuel pump.  Just getting "meter" readings is helpful.  Given a choice, I'd prefer some digital oscilloscope testing for amperage, because you can test the amperage for EACH BAR of the motor armature, and using the 'scope cursor feature, it's easy enough to also verify the motor RPM.  Everyone thinks of fuel pump failures as being a pump failure--but--it can just as easily be the failure of the electric motor powering the pump.  I've already harped on the potential for failure of the wire harness and fuel pump relay that supply power and ground to the electric motor.

 

I'm trying to do it right but I have a half tank of fuel in that I can't get out,

 

If the pump still has any life in it, you can disconnect the fuel filter line and short the fuel pump prime connector to the aux batt terminal (that loose wire near the aux batt terminal).  That should run the pump and pump the fuel out. 

My pump worked OK.  I took a length of fuel tubing, formed a proper end on it, and stuffed it into the fuel tank plumbing where it would have attached to the fuel filter.  The formed end was nice, as it sealed nicely on the OEM fuel plumbing connectors.  I filled plastic fuel containers until the pump wouldn't move any more fuel.  There was still just a little left in the tank.

 

Lumina_Fuel_Pump_01.JPG

 

Lumina_Fuel_Pump_02.JPG

 

It just now occurred to me that, since there's almost no pressure in the open-ended tube, there's also little reason to form the rib that secures the tube in the OEM plumbing.  I bet I could have jammed the raw tubing into the tubing connector at the fuel pump, and been fine (as long as the end of the tubing had no burrs to cut the sealing O-ring.)

 

As already said...you're going to disconnect the fuel filler hose anyway, so that's another entry-point for stuffing in a siphon hose to do it the "old-fashioned way".  Doesn't rely on the fuel pump working, just suck and spit.

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To add to the post above:  General electrical-system testing:

 

Voltage to the pump has to be tested as close to the pump as practical, which essentially means at the harness connector closest to the fuel tank.  It's been a few years, I don't remember if that connector is inside the trunk or under the trunk floor.  Kinda thinking under the trunk floor.  I disconnected that connector, made a jumper harness, then probed the jumper harness so I didn't harm the vehicle wiring.  Voltage to the pump will be lower and lower the farther to the rear of the car you go--and the pump doesn't care what voltage is at the battery or at the alternator, what matters is what voltage is at the pump.  Of course, you can't get inside the tank to see what evil happens in the in-tank wire harness, which is why it's so important to replace it while the tank is out and apart.

 

I want to see system voltage (battery voltage with engine shut off, or alternator voltage if the engine is running) at the fuel pump, with the fuel pump RUNNING.  Realistically, I'd happily accept system voltage minus about 1/4 volt.  Testing on my two Luminas showed over a volt lost in the + harness--a little bit of loss at every place I tested.  Similar with the ground side--you'd like to see no more than 1/4 volt remaining in the ground wiring, and I had a full volt.  If the ground wiring were "perfect", there'd be no voltage at all, because all the voltage was getting back to the negative side of the battery, or alternator.  End result, with the engine running and the alternator throwing 14.2 volts, the pump was running on barely 12 volts.  With the starter cranking, battery voltage was down to 11 volts, fuel pump was running on about nine.  Far as I can tell, that's "normal" for these cars.

 

Amperage, on the other hand, can be tested anywhere in the circuit dedicated to the fuel pump--it doesn't have to be tested "next door" to the fuel pump.  I use a clamp-on inductive probe attached to the 'scope, but I could just as easily pull the fuel pump fuse and connect my ammeter leads to the two sides of the fuse socket.  With the pump running, I'd expect something like 6 amps.  Low amps can mean high resistance in the circuit, high amps can mean that one or more armature bars have shorted to ground--or--the fuel filter is getting plugged.

 

The real magic is the 'scope pattern; and I don't have photos of that with my Lumina.  I do have some from the fuel pump job on my '88 K1500 pickup, though.  If you have access to a digital 'scope and a low-ampere probe, you might want to look at post #2:

http://www.thirdgen.org/forums/tbi/612473-tbi-fuel-pump-upgrade.html

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There is a YouTube video showing W Cutlass ( not vert) fuel tank removal, replacement. Looked very similar underneAth to my 92 vert. Didn't look that hard and I'm a novice mechanic. But, I would not do one myself even though I'm skinny. I have no ramps, jacks, etc. driveway on slope. I just wanted to see what operation looked like since so many of you discuss this on here.

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Thanks for all the responses I just got the tank down and put the new assy in . Ready to reinstall after a much needed break. Like I was saying I'm 6'6" tall 280# and I don't fit real well in all those little nooks and crannys under there . Heck I had a hard time just getting under the car . I can't tell how many times I banged into things and I'm doing this by myself . But I'm on the downhill side now and I really feel like I've accomplished something and saved a lot of money I don't have I'm on disability from work so don't get much. I find it very hard to believe someone did this job on the side of the road in an hour. That guy must be a magician. But thanks again to all of you. Fred

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Oh and it turns out there wasn't a half tank in it. Apparently the float fell off and was just rolling around in the tank. There was hardly any fuel in it at all. Now I'll know everything is new in there and that's a good feeling. :-)

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