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Fuel Pump Fuse Blowing

amo1dun

By amo1dun,
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amo1dun NPORA Regular

amo1dun

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89 Pathfinder 4x4 Auto

 

ok here we go....

About 2 months ago while driving down a hill, decelarating, and taking a turn the truck shut off. Fuel pump fuse was blown...had a spare 10a, put it in and ran until...

Last weekend the 10a fuel pump fuse started blowing when trying to start, wont start. Unplugged FP connector, key in the on position or cranking doesnt pop a 10a fuse. Plug in FP connector pops 10a fuse and the Pump wont run. Put in a 15a...doesnt pop with the fp connected, but pump wont run. Swapped FP relays and pops a 10a but not a 15a but the pump wont run. Inspect harnesses, no visual damage or shorts that i can see. Confirm battery voltage at fp connector with key on(while connected) with 15a fuse in. Install new FP and 10a fuse and guess what :scratchhead: the fuse pops and the PUMP WONT RUN! :wtf: Hotwire old pump for @!*%s and giggles and it runs. Dont think its a dead short, not blowing 15a.

 

Now im thinking Crank Sensor and/or circuit or ecu is toast. Ecu has to get a 1deg signal from the CAS for the pump to turn on(when the key is turned to on position)

 

Im losing it here...anyone with some insight

 

Pathfinders pffffhhhh :wackinit:

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nunya NPORA Old-Timer

nunya

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The float assembly for the fuel pump shorts out, in turn pops the fuse. When you did the fuel pump did you replace JUST the fuel pump or the float assembly and all?

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amo1dun
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amo1dun

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The float assembly for the fuel pump shorts out, in turn pops the fuse. When you did the fuel pump did you replace JUST the fuel pump or the float assembly and all?

 

Just the pump....and what do you mean the float assembly shorts out? That would just mean the gauge wouldn't work, correct? Gauge works

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nunya NPORA Old-Timer

nunya

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NOpe, gauge can still work, that wiring still gotta go from the plug to the pump for the pump to actually work and it IS a 20 year old chunck of metal with wires runnin through it. I've had to do it on 2 different d21s I had for the same reason. Takes a little more juice to run the pump than the gauge

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amo1dun
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amo1dun

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NOpe, gauge can still work, that wiring still gotta go from the plug to the pump for the pump to actually work and it IS a 20 year old chunck of metal with wires runnin through it. I've had to do it on 2 different d21s I had for the same reason. Takes a little more juice to run the pump than the gauge

 

:scratchhead: what exactly are you saying? You think I need the whole intank assembly w/

harness? I dont even think they sell that @!*%

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nunya NPORA Old-Timer

nunya

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When you took the fuel pump out... The thing it's connected to that actually bolts to the tank. That piece. Where the wires go through it, the little round "buds" on the top, they short in there. You don't need to re-wire the whole truck or replace the whole fuel system, I guess some things are harder to explain over the Internet :shrug:

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GrimGreg NPORA Old-Timer

GrimGreg

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:scratchhead: what exactly are you saying? You think I need the whole intank assembly w/

harness? I dont even think they sell that @!*%

Yep, best to replace the whole assembly, part # for your truck is 17040-WD21001

 

http://www.courtesyparts.com/17010y-pump-assy-fuel-pathfinder-wd21-08/1987-08/1989-vg30i-07/1986-08/1987-vg30i-p-539988.html?cPath=5572_5573_5590_5595&

 

If you do just want a new cap piece with the wire tail; http://www.courtesyparts.com/25060-gauge-assy-unitfuel-tank-pathfinder-wd21-07/1986-08/1987-w/2d-2wd4wd-cyl-07/1986-08/1987-w/2dv/2d-4wd-p-540051.html?cPath=5572_5573_5590_5595&

 

Most vehicles you HAVE to buy the entire assembly.

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amo1dun
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amo1dun

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When you took the fuel pump out... The thing it's connected to that actually bolts to the tank. That piece. Where the wires go through it, the little round "buds" on the top, they short in there. You don't need to re-wire the whole truck or replace the whole fuel system, I guess some things are harder to explain over the Internet :shrug:

 

So from what I described you think the sending unit/harness assembly is the culprit? It does only blow the 10a fuse when the harness is connected...but why wont it blow a 15a fuse and still not allow the pump to energize?

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amo1dun
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amo1dun

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:suicide: I aint buying one new thats for sure.

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Simon NPORA Old-Timer

Simon

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It's the connections on top of the sending unit. Guaranteed they're corroded. I had to jumper 3 different sending units on 2 different trucks for the same reason. It's typically the + power wire to the fuel pump that gets the worst. What I did was cut it off, drill through the sending unit, feed the wire through, and then solder it so the wire for the fuel pump. I then used a decent gas resistant sealant to seal the hole, which works for about 6 months. :lol:

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  • 1 month later...
amo1dun
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amo1dun

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Still have the problem.....Does anyone know if a sending unit from a 95 will swap with an 89, part numbers are different but the unit looks almost identical, 4 wires on top, 2 for the gauge 2 for the pump and a ground? Its almost ridiculous at this point...I cant get this figured out and its been over a month.

 

PS- Brand new fuel pump BTW

 

Problem:

 

1) Blows 10amp fuse with key on engine off

2) Doesnt blow 15amp fuse with KOEO but pump wont energize

3) Ground introduced at FP relay due to no ground signal on ecm side(supposedly :wackinit:)

4) Starts with 10amp, pump energized and it runs like @!*% for 1 mile then shuts off...fuse blown.

5) 15amp fuse put in and blows with key on engine off...

6) 20 amp fuse put in doesnt blow with KOEO but pump wont energize

7) Resplice FP relay back to OEM

 

Now-

Engine starts but stops immediately with a 15amp fuse in place....but

1) Blows 10amp with KOEO with pump connected, doesnt blow with FP disconnected

2) Doesnt blow 15amp with KOEO

 

12v at FP relay with key on engine off, 12v at main harness side of FP connector but pump wont energize

 

:wtf:

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  • 2 weeks later...
amo1dun
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amo1dun

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Thanks to all that responded... Nunya you sir are the man!! Picked up a sending unit from a dude on CL swapped it out and its alive!!!! not blowing the fuse, no sputtering, no hesitation finally shes back on the road.

 

PS- The sending unit was from a 95 and my truck is an 89...although part #'s are different....it seems to be working just fine, it hasnt ran this good in a while :friday:

 

thanks

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