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Solved losing my mind over this damn fuel gauge

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franki cacuz

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City, State
elmsford
Year, Model & Trim Level
2002 ford explorer 4 door
i looked and read everywhere and nothing is helping..

2002 explorer 4.0 sohc

i put in a new complete fuel pump in this thing. the first pump a napa no fuel gauge the second a delphi worked for like 2 minutes then nothing. then one more delphi and nothing.

before i threw in the new pump assembly it worked.

symptoms. when i turn the truck on the gauge sweeps and when in test mode it does to. last night i disconnected the battery turned it on today fuel gauge swept and dropped to E but a tick up from last night then 3 mins later it dropped all the way down and check gauge came on.?

where do i start? any help is appreciated fellas.
 



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I’d start at the electrical connections. Unlikely to get 2 bad ones, although it’d be possible.
 






i tried 3 smh...

any idea where i can find a diagram. I'm going to start at the plug. i honestly think its something retarded i looked at the wiring when it was down didnt notice anything. my initial guess is a bad ground some where this is my second explorer not so familiar with them im a jeep guy
 






i looked and read everywhere and nothing is helping..

2002 explorer 4.0 sohc

i put in a new complete fuel pump in this thing. the first pump a napa no fuel gauge the second a delphi worked for like 2 minutes then nothing. then one more delphi and nothing.

before i threw in the new pump assembly it worked.

symptoms. when i turn the truck on the gauge sweeps and when in test mode it does to. last night i disconnected the battery turned it on today fuel gauge swept and dropped to E but a tick up from last night then 3 mins later it dropped all the way down and check gauge came on.?

where do i start? any help is appreciated fellas.
 






This is a single wire that goes from fuel tank to instrument cluster
You should look for any breaks in the wire
A continuity and wiggle test is a good idea
You can check the ohm of the fuel sender when the tank is down and then again check that same signal at the instrument cluster

There is also an “anti slosh” module in the instrument cluster that can cause issues w the fuel gauge
 






This is a single wire that goes from fuel tank to instrument cluster
You should look for any breaks in the wire
A continuity and wiggle test is a good idea
You can check the ohm of the fuel sender when the tank is down and then again check that same signal at the instrument cluster

There is also an “anti slosh” module in the instrument cluster that can cause issues w the fuel gauge
i bet its that wire.. or the module. i took this thing down 3 times 3 different pumps. im going to make that worse case scenario. you think i can find that wire without taking it down or am i screwed and theres no way around it.

my bad for all the questions i havent worked on one of these sice my 02 sport trac 10 + years ago
 






There are no bad questions

Yes you can access the fuel tank wiring harness on the frame rail just above the drivers rear tire,
Good spot to begin testing without having to drop the tank
 






i tried 3 smh...

any idea where i can find a diagram. I'm going to start at the plug. i honestly think its something retarded i looked at the wiring when it was down didnt notice anything. my initial guess is a bad ground some where this is my second explorer not so familiar with them im a jeep guy
1. You need Too start at the gas tank connector( fuel pump sender). Disconnect the connector at the fuel tank.
2. Uses a multi meter and set it on resistance scale and ring out the connector/ wire black/ yellow stripe which goes ground check if it goes to infinity 0.0. There is a slice s234 and black/ white stripe that goes to ground G101.
G101 does not make sense because its located on LH front of engine compartment, near radiator.
3. Once that you verify a path too ground. Go too next step.
4. at the fuel tank connector , look for yellow/white stripe wire at the connector.
a) Turn the ignition key on
b) check the gauge. It should be at E
c) ground the yellow/white stripe to ground. The gauge should be at fuel.
If not.
The is a slosh module that fails between the gauge and the sender unit.
The large blue capacitor that fail. The slosh has 6 slide pin connectors on it.

Which share it's ground with fuel gauge, voltmeter, oil pressure, and speedmeter.
The power is share by fuel gauge, voltmeter, oil pressure
If the other gauge you know the power and grounds are good.
I have not figure out the pin order on the slosh board connector.
This ford slosh module design has not change in over 30 years. Just the slide pins and group gauges. The first design uses color coded wires.
 






1682436463723.jpeg
 






Did you replace both the fuel pump AND the fuel pump assembly? Did you try entire assembly units with the NAPA and the Delphi pumps? Those fuel pump assemblies are available at such low cost, that quality seems like a possible issue.

Does the fuel pump work? Did both fuel pumps work?

Did you possibly get the float snagged on anything?

Is there any particular reason you replaced the entire assembly, and not just the pump?

Do you still have the OEM assembly? You could always put the OEM assembly back if it is still available. That would tell you if the replacement units are the issue.

You could also fill the tank to the top, track your mileage on your trip meter, and refill every 150 miles, or something like that. Depends on how you feel about your truck,..

Do you have a fuel tank access panel?

Good luck.
 






Did you replace both the fuel pump AND the fuel pump assembly? Did you try entire assembly units with the NAPA and the Delphi pumps? Those fuel pump assemblies are available at such low cost, that quality seems like a possible issue.

Does the fuel pump work? Did both fuel pumps work?

Did you possibly get the float snagged on anything?

Is there any particular reason you replaced the entire assembly, and not just the pump?

Do you still have the OEM assembly? You could always put the OEM assembly back if it is still available. That would tell you if the replacement units are the issue.

You could also fill the tank to the top, track your mileage on your trip meter, and refill every 150 miles, or something like that. Depends on how you feel about your truck,..

Do you have a fuel tank access panel?

Good luck.
I'm certain it did not snag we were very careful but even when we manually move the flow outside of the tank I got no movement

The OEM assembly unfortunately was thrown out by accident

All three pumps complete assemblies marked It was one Napa two delphi's no access panel considering cut ting one though The pump was completely dead even when we gave it direct power so we changed everything

I just took the cluster out opened it up made sure there was nothing burned up in there everything seems in order I'm about to start tracing wires now with the volt meter and that's where I'm at.
 






I appreciate all the help boys I had a wire back out of the main harness that clicks into the cluster jumped it with two wires n two disconnects done...

16824541956193896937522258048274.jpg
 






SOLVED.

So just odd timing? Fuel pump replaced AND cluster wire comes loose.

Glad you got it.
 












SOLVED.

So just odd timing? Fuel pump replaced AND cluster wire comes loose.

Glad you got it.
it had junkyard marks on the cluster someone screwed with this at one point. I'm thinking when they tried to unclip it they pulled the clip apart at the wires. hopefully the gauge makes its way to empty as I drive it, I over filled it and I'm in 30 miles fingers crossed lol. thank you for all the help boys.
 






I have a 2002 Explorer XLT 4WD, 4.0 gas engine. A week ago I went to start it to take it for inspection and it wouldn't start. I had been sitting for a couple of months and I hit it with some starting fluid and it started and ran fine for 10 minutes. Shut it off, went inside and came back out and it not only wouldn't start, it wouldn't even turn the starter.

Fast forward a few days, had a locksmith come out and check the key (I only had one) and see if the chip went bad, but he said the chips rarely do, but that he couldn't load the key so he felt the computer was bad. Ordered a computer with 2 keys, but keys still aren't recognized. Replaced the pickup coil around the ignition, and now cranks, but won't still start. Checked battery, fuses, relay, collision impact cutoff switch, etc. and are all good. Can't hear the fuel pump running, so I jumped the fuel pump relay, still no joy. I am thinking the fuel pump went bad which is weird? Checked for fuel pressure, zip!

Here's the strange part, the fuel tank is full, but the gauge shows empty. Also, the horn stopped working as well. I pulled the clock spring and tested it, and the horn circuit tests fine through it.

In my mind, the fuel pump and the fuel gauge stopping at the same time make me think there's a connection, but since it's literally impossible to find the correct schematics for this vehicle, I'm left with an educated guess. Does the fuel gauge need power or is it just a resistive circuit? Either way, it's possible it's a wiring issue since they are both in the same unit and I am guessing the same wiring harness/connectors?

Also, my explorer is a 2002, but was built in August 2001, and I went searching for the horn relay, but that socket is empty and there's no terminals in it either, so it looks like it never had a relay. The horns work when I use the remote to lock the vehicle, so I know it's not the horns which it has 2.

I tried grounding the horn wire connector under the dash after tracing it through the clock spring and the horns still won't work. The fact that I can't find the correct wiring schematic isn't helping here as the horn circuit must be integrated into some other component, possibly the PATS? I'm a electronics tech and I can read schematics and use a meter, but without the correct diagrams, I'm just guessing.

Can anyone suggest any ideas? I've check every fuse in the vehicle and cannot solve this. My next step is to pull the gas tank, but doing that on the ground isn't my idea of a fun day.

Also, if anyone can point me to the correct wiring schematic for this vehicle, I would greatly appreciate it!

Thanks in advance!

2002 Ford Explorer
XLT 4WD 4 Door
4.0 Gas Engine
 






Okay first up

The pats key

The theft light will go out while cranking the starter
If it does then the pats system is happy with the key and no need for a locksmith
If the light flashes rapidly then there is an issue with the pats system

With a rapid flashing theft light you can retrieve the pats trouble code

With a rapid flash you can crank the starter all day long and it will never run
If the theft
Light goes out while cranking it is not a pats issue causing the now start

Fuel pressure
You can check for power at the fuel tank connector. It is located on the frame rail just in front of the drivers rear tire
When you turn the key to start/run the computer should run the fuel pump for 1-2 seconds
If you have power here then you can rule out the pcm the fuel pump relay, the fuse and the inertia switch. You can also now run battery power to the pump and see if it runs and builds pressure. Should be 64 psi +/- for a 2002

The wiring schematics are available I usually just buy a book on eBay 01-04 sport wired very similar to 98-01 explorer

Since it started with ether I would suggest you have a fuel pressure issue or fuel pump power issue

Hope this helps
 






Okay first up

The pats key

The theft light will go out while cranking the starter
If it does then the pats system is happy with the key and no need for a locksmith
If the light flashes rapidly then there is an issue with the pats system

With a rapid flashing theft light you can retrieve the pats trouble code

With a rapid flash you can crank the starter all day long and it will never run
If the theft
Light goes out while cranking it is not a pats issue causing the now start

Fuel pressure
You can check for power at the fuel tank connector. It is located on the frame rail just in front of the drivers rear tire
When you turn the key to start/run the computer should run the fuel pump for 1-2 seconds
If you have power here then you can rule out the pcm the fuel pump relay, the fuse and the inertia switch. You can also now run battery power to the pump and see if it runs and builds pressure. Should be 64 psi +/- for a 2002

The wiring schematics are available I usually just buy a book on eBay 01-04 sport wired very similar to 98-01 explorer

Since it started with ether I would suggest you have a fuel pressure issue or fuel pump power issue

Hope this helps
Hi Fortune!

Thanks for the info!

The PATS is ok as I had a locksmith come out and reload the key and make me a spare. If the PATS was the problem, like it was when I first started having trouble, the engine wouldn't even crank. It cranks now, and will run for a few seconds with starting fluid, so It's my impression it's a fuel issue.

I have checked the fuses, the FP relay has power and the inertia switch is not tripped and shows power coming out of it.. All of those check good! I have no power at the fuel pump connector, but it has a good ground, and I pulled the pump and tested it and it's working fine. I started looking for the fuel pump driver module, but it seems this model doesn't have one! Is that correct if you know?

I don't think there's anything else in between the inertia switch and the fuel pump, but I don't have a lift to trace the wiring under the vehicle!

I'm ready to jump power to the pump to see if it runs, but I'm concerned that I might damage something else, like the computer or?? This model was built in August of 2001, but called a 2002. Everything I try to look up keeps saying it's supposed to have this or that, but it doesn't match the 2002 or 2002 details? I'm at a loss here, so if you have any other suggestions, please let me know. I'm going to go look on eBay for schematics as you suggested.

Thank you VERY much!

Tom
 






Okay first up

The pats key

The theft light will go out while cranking the starter
If it does then the pats system is happy with the key and no need for a locksmith
If the light flashes rapidly then there is an issue with the pats system

With a rapid flashing theft light you can retrieve the pats trouble code

With a rapid flash you can crank the starter all day long and it will never run
If the theft
Light goes out while cranking it is not a pats issue causing the now start

Fuel pressure
You can check for power at the fuel tank connector. It is located on the frame rail just in front of the drivers rear tire
When you turn the key to start/run the computer should run the fuel pump for 1-2 seconds
If you have power here then you can rule out the pcm the fuel pump relay, the fuse and the inertia switch. You can also now run battery power to the pump and see if it runs and builds pressure. Should be 64 psi +/- for a 2002

The wiring schematics are available I usually just buy a book on eBay 01-04 sport wired very similar to 98-01 explorer

Since it started with ether I would suggest you have a fuel pressure issue or fuel pump power issue

Hope this helps
Hello again Fortune!

Ok, so I powered the fuel pump up off my 12v battery box and the vehicle starts and runs great! The wiring that I have found shows the power goes from the relay, to the inertia switch, (and I have power at the inertia switch), but nothing at the pump. I don't see anything in between so it has to be a wiring issue, but I can't find anything that shows where the wires are routed from the inertia switch to the pump? The fuel gauge also stopped working, although there's power on several pins in the fuel pump connector which has 8 pins.

If you have any ideas, please let me know and thanks for the help! I was able to cut a hole in the floor with my Dremel tool.

Cheers

Tom
 



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Hi Fortune!

Thanks for the info!

The PATS is ok as I had a locksmith come out and reload the key and make me a spare. If the PATS was the problem, like it was when I first started having trouble, the engine wouldn't even crank. It cranks now, and will run for a few seconds with starting fluid, so It's my impression it's a fuel issue.

I have checked the fuses, the FP relay has power and the inertia switch is not tripped and shows power coming out of it.. All of those check good! I have no power at the fuel pump connector, but it has a good ground, and I pulled the pump and tested it and it's working fine. I started looking for the fuel pump driver module, but it seems this model doesn't have one! Is that correct if you know?

I don't think there's anything else in between the inertia switch and the fuel pump, but I don't have a lift to trace the wiring under the vehicle!

I'm ready to jump power to the pump to see if it runs, but I'm concerned that I might damage something else, like the computer or?? This model was built in August of 2001, but called a 2002. Everything I try to look up keeps saying it's supposed to have this or that, but it doesn't match the 2002 or 2002 details? I'm at a loss here, so if you have any other suggestions, please let me know. I'm going to go look on eBay for schematics as you suggested.

Thank you VERY much!

Tom
Hello again Fortune,

So the locksmith who came to see what the problem was, was wrong. Eventually I figured out that it wasn't the PCM that was bad, it was the chip pickup coil around the ignition switch that was bad.

Fortunately that fixed the PATS issue, but the vehicle still would not start, the fuel gauge didn't work, and the horn also didn't work. Really strange problems by themselves! Luckily I have lots of patience.

Today I finally resolved the problem after 2 weeks of troubleshooting and cutting a hole to access the gas tank and fuel pump to eventually tracking down a bad connector feeding power to the fuel pump, the fuel tank gauge and also the horn.

I found that all three circuits ran through the same harness and a common connector and fixed all three issues and using my toner wire tracer was the trick to finding the wire routing. There is a 2" X 3" connector with about 30 pins under the passenger side dash right above the inertia switch. It has a bolt in the center just like the connectors in the engine compartment for the PCM. That bolt was loose and the connector must have wiggled out and that is where the 3 circuits ran through. Tightened it up, and that fixed all 3 issues. I do not know how that got loose, as I have never touched that connector, and have never had any issues with it since we bought it new, so I can only assume it was never tightened at the factory. Must have been made on a Monday or Friday I guess.

I spent 3 hours putting the vehicle back together today and all is working perfectly.

Thank you for your time and help!

I have a bunch of wiring diagrams I'm posting here. Hopefully they may help someone else down the road.


Cheers

Tom

Fuel Pump Circuit.jpg


Horn Wiring.png


Image 1.png


Diagram 1.jpg


Diagram 2.jpg


Diagram 3.jpg


Diagram 4.jpg
 

Attachments

  • FuelSystemTheoryandOperation.pdf
    724.5 KB · Views: 31
  • FuelSystem.pdf
    274.9 KB · Views: 27
  • FuelPressureSpecifications.pdf
    31.3 KB · Views: 25
  • 2002FordExplorerV64.0LEnginePerformance.pdf
    279.9 KB · Views: 26






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