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Fuel sender/pump unit switched out 1993 WD-21 pathfinder


westslope
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The fuel sender unit tends to fail on older models of WD-21 pathfinders.  Ours was registering from full to 3/4 of a tank, and then from 1/4 of a tank to empty but was behaving erratically between 3/4 and 1/4 of a tank.

 

The dealer wanted in excess of $300 for a new part.  I located a used unit for about $115.  Finally, I decided to go for a $25 unit at a wrecker's that I removed with some difficulty from a 1994 pathfinder in good, no excellent condition (e.g., virtually no frame rust).

 

 

The fuel sender/fuel pump unit sits on top of the fuel tank and can be accessed by removing the carpet from the rear storage area. Start by unscrewing the flat plastic panel at edge of the cargo space.  .  This exercise was somewhat intimidating so I typed out a complete list of what I needed to do.  First photograph of rear cargo space with list follows.

 

 

 

 

IMG_2146_1.jpg 

 

 

 

 

The fuel sender wires plug into another plug that is accessed by crawling under the rear right of the vehicle and looking straight up. The fuel sender unit plug is attached to the chassis with a plastic clip.  This clip and the plug can be separated.  With difficulty I removed the plug and clip together at the wreckers.  At home, I simply removed the plug and left the part that clips into the chassis intact.  Tedious.  I wore goggles to keep the dust and dirt out of my eyes.  Previously I had cleaned out the plugs and clips with a toothbrush.  Sorry no photos.

 

Early preparations

 

Prior to starting, I prepared for this job by buying an O-ring from the local Nissan dealership.  The old one cannot be reused.  I also soaked the bolts attaching the unit to the gas tank and screws attached to the fuel lines with Krown Rust anti-rust and lubricating oil.  I didn't want the bolts attached to the gas tank to snap.

 

 

 

 

Remove the carpet by unscrewing the rear plastic retainer and the cargo tie-downs. Disconnect the side plastic walls as required. Remove the jack cover.  Removing the jack might makes things easier but is not necessary. 

 

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I placed the screws in the jack plastic cover.

 

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Before starting to remove the gas lines and the actual unit, the received wisdom is to pull the fuel pump fuse and start the engine 3 times after it initially dies.   I pulled the wrong fuse.......  but had already unplugged the fuel sender unit so no harm.  I also opened the fuel in-take valve to equilibrate pressure.

 

Note, that I have removed the gasoline lines and placed large screws in the end to prevent (more) spillage and dirt from entering.

 

IMG_2147_1.jpg

 

 

 

 

Here is a closer look from the top of the old unit.  Note how the white caps on the fuel sender wires appear cracked and dirty?  I believe that is the source of the problem.  If had known to act earlier, I would sealed those white plastic caps with glue or sealant of some kind.

 

Tungsten covered some of these issues in a previous thread entitledFuel Sending Unit. Watch out!

 

IMG_2149_1.jpg

 

 

 

 

The following is not a great photo--my apologies.  What you see is the old unit on the left and the new unit on the right.  

 

IMG_2150_1.jpg

 

 

 

 

I did use a resistance meter to test the 'new' unit and quickly test the old unit.  Informative.  In the above picture, those things that look bars of yellow soap actually are floats that move up and down with the level of gasoline in the tank.

 

Another view follows:

 

IMG_2151_1.jpg

 

 

 

 

I cleaned up the new unit a bit and wonder if I should paint with rust paint like trem-clad or simply soak with a rust inhibitor at some point?

 

Unfortunately I forgot to take photos once I removed the original unit.  I covered the whole with a cloth when not working around it.  I did my best to clean the O-ring track with a soft cloth.  I used a vacuum cleaner to gather loose material and minimize debris falling into the gas tank.  The odd piece of rusty dirt that fell in was removed with the use of a telescoping magnet.  

 

Removing the clips from the two gas lines and forcing the gas lines on the new unit was tedious.  

 

In the end, it works!  I drove to the Petro-Canada station and filled by 20 litres at a time, checking the fuel gauge along the way.  Success. 

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My fuel gauge only shows 3/4 full when I fill it up, and once I use a half tank it just stips registering at all. I thought it was the voltage regulator. But your symptoms sound more like mine. Do you think that this is what is wrong with mine?

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Next time, think twice before using a vacuum around an open gas tank. Besides the fact you can pull fumes into a running electric motor, they tend to generate a lot of static electricity. :crossedwires:

Thank you GrimGreg.  Yes, in hindsight, maybe that was not so smart.  On the bright side, the gas would have burned, not exploded. (I think....)   But yeah, next time, maybe I won't use an air-moving electrical device close to an open gas tank.  Excellent point.

 

 

Question:  How can one clean the O-ring groove and surrounding area without knocking dirt into the gas tank?  Presumably there is a better and safer way than using an electrical vacuum cleaner.

 

 

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Did you ever figure out what was actually wrong with your original unit?  The pictures seem to just show the plastic caps being insulators for feedthroughs (the wires just start up again inside).

The photo quality is poor; I apologize.  

 

The two plastic cap insulators for 'feedthroughs' in the middle were cracked and dirty.  That happens to coincide with the fuel gauge not working between 3/4 of a tank and 1/4 of a tank.  We quickly tested the old unit after it came out for resistance and the resistance seemed to bounce all over the map for the 3/4 to 1/4 levels.

 

 

So I'm guessing that plastic insulator caps were broken and corrosion resulted.

 

 

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That filter on the bottom of the pickup tube on the old unit looks like it was full of crud. Was it?

 

Yes.  Well, it appeared to have lots of crud in it.   The filter on the 'new unit' looked a tad dirty.  I wasn't sure how to clean it or if cleaning it was really necessary.  

 

Question:  Should have I have cleaned that filter and how critical is that?

 

 

 

 

Tungsten:  The fuel fill cap?  Yes!  (Silly me....) 

 

 

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My fuel gauge only shows 3/4 full when I fill it up, and once I use a half tank it just stips registering at all. I thought it was the voltage regulator. But your symptoms sound more like mine. Do you think that this is what is wrong with mine?

Very likely.  I will also go out on a limb here and say that you should check the chassis seams on your vehicle beneath the rear passenger seats and the rear portions of frame for rust.I would verify the fuel sender/pump unit as well as these vulnerable seams at the earliest opportunity but be prepared to proceed slowly, perhaps soaking screws with penetrating lubricant for a couple of days.

 

Help!

 

Speaking of which.  I tried to remove the carpet from the cargo space closer to the front of the vehicle and could not because a couple of cargo-tie-down holder screws are corroded in place.   I would rather not rip up the cargo space carpet.  Any suggestions for getting these screws out?  I have already worn the heads on a couple of them (FYI I am a large male and perfectly capable of snapping bolts -hehe-). 

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Help!

 

Speaking of which.  I tried to remove the carpet from the cargo space closer to the front of the vehicle and could not because a couple of cargo-tie-down holder screws are corroded in place.   I would rather not rip up the cargo space carpet.  Any suggestions for getting these screws out?  I have already worn the heads on a couple of them (FYI I am a large male and perfectly capable of snapping bolts -hehe-). 

Either try a rounded bolt head remover type tool, or cut the heads off, then drill out the rest and retap the hole. I have one tie down that I haven't replaced in my 93 because I broke the bolt heads off, on my 88 they all broke, and I just reinstalled them with self drilling screws. Not like the hold a heavy load anyway.

 

As far as cleaning the gasket surface, when my o-ring went bad, I dropped and emptied the tank, then took a wire wheel to the surface, then wiped the seat and inside of the tank with paper towels. If I were to do it without dropping the tank, I might make some sort of plug out of a plastic lid, a screw and some duck tape. Put the screw through the middle of the lid, and tape around the edge, stick it into the tank holding it by the screw and then pull back up to stick the tape on the inside. Wipe the rim with a 3m/ green pad then use an old paint brush to broom the debris away. Yank out the lid and tape afterward. :shrug:

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rounded bolt head remover type tool  Thanks.  I do not use the cargo-strap tie-down buckles but simply want to examine the condition of the metal floor.

 

 

 

 

I can readily see the advantage in dropping the entire tank.  With no hoist or ramps, I went the other route.  

 

Should I think about dropping the tank and cleaning it as preventative maintenance at some point?

 

 

 

 

 

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  • 3 years later...

@Westslope - thanks for the write-up! My gauge is pretty wonky AND gas pisses out of the o-ring when the tank is full, so I have two good reasons to follow your lead on this!

 

@GrimGreg - how reasonable a job is it to drop the tank? I have two steel ramps but that's about it... that's a great jimmy-rig idea for cleaning the gasket area, but I think I'd rather drop the tank if possible... if I don't drop the tank I'll definitely end up using a vacuum cleaner regardless of the disclaimers...

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I dropped mine to replace it. Ramps help a lot, as does taking the rear fender flares off and pulling the gas filler completely out before trying to move the tank. How rusty is your rig? If the bolts are rusted in, you're gonna have a bad time. I broke several of the tank bolts trying to get them out. Getting it back in is also fun, especially the part where you hold it up with your knee while trying to get the bolts to thread. You can use a jack but put a board on the top or you'll dent the tank.

 

The plastic lid sounds like a great way to go!

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I did a little recon on this... WD-40'd every bolt I could see, popped the sender out to take a peek...

 

The MORON who I bought this from put the wrong sized O-Ring in! It was so damn big, a good 1/2 to 1 inch of the rubber was fully out of its seat, literally holding the flange off its mating surface.

 

I might as well have had a big salad bowl for a gas tank, bloody gasoline sloshing all over the place. I can see this guy's fingerprints all over the vehicle... everywhere he has touched it something is broken, his 'handy' work is unbelievable.

 

Soooo many cuss words are being withheld here... Grrrrr...

 

On the bright side... I have a good idea why my gas mileage on the first part of the tank is so terrible. And I don't have to look into the vapour filter system for why my rig stinks like gas.

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I tried the lid, it does indeed work very well. A standard yogurt container lid is JUST big enough. I put tie-wire through it, then laid a long bar of metal across the opening which I tied the wire too... this held it in place.

 

Also, turns out I'm the asshole... the O-rings seem to be built to expand when used or when they contact gas? Anyway, mine went in the right size and came out too big, just like the first one was when I pulled it out. So ya, you definitely cannot reuse them, heads up on that. Except I did reuse mine, I just cut about a centimeter out of it so that it became the right size again. So far so good.

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