Electrical issue need help asap

[JOlsen]

ok here’s the scenario. Last night driving home my fuel gauge dropped to empty and low fuel light came on. I know it isn’t low because I filled up less then 2 days ago. Just in case I stopped and tried to fill up and got 2 gallons in before it was full. So I know there’s gas. Now today I looked under to make sure the harness was connected well and the black/orange tracer wire in the plug was smoking hot. Does anyone have a diagram they can show me of what this wires normal state is supposed to be so I can try and trace the issue. Or anyone else had this problem... HELP

 

[1955moose]

Sounds like your sending unit is overheating due to a short. I'll send a pic of schematic if I can.

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[Sgt Darkness]

Best way to check for a possible hot wire that is grounded is to take ur voltage tester put the black wire on the negative post of the battery and then the red wire on a known ground. Your tester will let u no if u have a hot ground or not by showing voltage or no voltage on you tester. Good luck!!

 

[JOlsen]

I have verified that the black/orange tracer is at rest ground. But when the vehicle is running it it sending power back down that line from the pump side.

 

[JOlsen]

Still need help guys pls

 

[Plati]

Still need help guys pls

What is your vehicle … year … model … engine?
Where is that connector you refer to?

Is it possible to buy a wiring diagram and or shop manual?
Where is best place for that, a manual in this case could pay for itself!

not sure if this applies to your vehicle … this is 2003 Expy
theres a blk/org for fuel pump motor?


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[JOlsen]

99 5.4 rwd. I have the Haynes manual but according to that it shows black/orange as a ground which it is at rest but when on the vehicle side stays ground and the pump side goes 12v. I have a new sending unit ready to be installed this weekend

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[JOlsen]

Now after reading your diagram it appears the vlack/orange should be + so any help in figuring this problem out would be helpful

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[JOlsen]

I should also add. The truck runs and drives fine that wire seemed to be the only thing wrong, and the fact that tanks full and it says low fuel on dash

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[1955moose]

The majority of grounds on this vehicle are solid black.

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[stamp11127]

The black/orange wire is for the sender connection to the instrument cluster.
I would disconnect the cluster and check that wire for "short to ground". Also check the resistance of the sending unit.

 

[Plati]

Just for the record that wiring diagram is 2003, not 1999.
I didn't know your year when I posted that.

 

[1955moose]

Thanks Stamp for the post. I was going to look up his wire in my 2000 book, but forgot the other day.

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[JOlsen]

Does anyone have the wire colors for 99? Like I said according to my Haynes manual it said ground

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[JOlsen]

The black/orange wire is for the sender connection to the instrument cluster.
I would disconnect the cluster and check that wire for "short to ground". Alao check the resistance of the sending unit.

Ok stamp I will try this Sunday. I definitely dont get what's going on so that would make some sense if it's the actual cluster. I have had an issue with the odometer reading since I got the truck and have just been too lazy to fix the cold solder problem

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[stamp11127]

Here are the diagrams for the engine performance section that includes the fuel pump circuit.

The cluster hasn't been proved to be the cause of your issue. You should check the harness first. The odometer is from cold solder joints usually.

 

[JOlsen]

Yeah I know about the odometer. I did separate the wire and the vehicle side stays ground. And the fuel pump side throws 12.4 volts. So I think the issue lies within the pump/sending unit
At least I hope. But I am not looking forward to dropping a tank with 25 gallons in it lol

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[stamp11127]

Measure the resistance between the black/orange wire and the yellow/white wire at the cluster or fuel pump connector.
Service manual test procedure for the gauge runs resistance between 15 and 145 ohms. If the sender reads close to 0 the sender is at fault.

If you have to drop the tank, remove the fuel ine at the rail or remove the inline fuel filter, add on a few feet of fuel line. Use the fuel pump to empty the tank into suitable containers. When you are ready to pump fuel just jump the fuel pump relay.

 

[1955moose]

How come pumps/sending units never fail on an empty tank? Its always within a day after we tanked up!

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[Plati]

How come pumps/sending units never fail on an empty tank? Its always within a day after we tanked up!

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Its because they fail on empty tanks. Really should never let your tank go empty.
That would be like going to fridge and there's no BEER in there

They fail on the transition from an empty tank to a full one, then when you fill it up and drive it you find out!!!