fixing messed up wire resistance

shop deals on amazon
Shop deals on ebay
Advertise with us
Ford SportTrac Forum

Help Support Ford SportTrac Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
T

Travis Munday

Well-Known Member
Joined
Dec 22, 2000
Messages
2,675
Reaction score
0
Location
Fayetteville, GA
I need to tap the intellectual resources here-



I recently removed my stock fuel tank and replaced it with one that is mounted in the bed. In doing so, I needed to extend the wiring harness that connects the fuel pump to the rest of the truck. Since I did, I increased the resistance of all the wires, the most important being the fuel level sensor wire that works off of resistance to get a proper fuel level reading. The truck threw up a CEL in protest. Now, how do I fix this overall increased resistance on this wire? I haven't checked resistances yet, but when low: resistance should be 22.5Ω, when high: 145Ω.



Right now, I've got probably 3/8 of a tank of gas, but I'm reading slightly below E. Of course, the new tank is taller then the old so the float will be lower for the same amount of gas. I"m trying to hold off on driving the truck until I can trust my fuel gauge again...
 
I doubt that is your problem. Adding a few feet of 16 ga wire would not change resistance by even a few hundreths of an ohm. Check all your splices to make sure you have continuity. Also, what was the CEL code. Maybe you don't have proper evac system connections to the new tank. That will trigger a code real fast. Probably what it is, not a wiring problem.
 
I have does this HUNDREDS of times. As long as you did not decrease the gauge (smaller wire) you will be fine. Seriously, I have done this no less than 200 hundred times. We have owned a repair shop for 23 years.



In theory you are correct, but in reality, it is such a insignificant amount it just does not matter..



What is the CEL code?
 
I'm not sure what the actaul CEL code was....it was read with a big fancy MAC code scanner that gives the code and what the code stands for, I was only told what the code stood for.



I'll have to nearly remove the bed to check my splices, but I was happy with the splices when I did them, all solder and no plastic. I won't be able to check them until Saturday, but I've got to pull the bed off anyhow...so no biggie.



I'll try to find out exactly what the code was.



After a quick search, these are soem codes I was able to find:

P0460 Fuel Level Sensor Circuit Malfunction

P0461 Fuel Level Sensor Circuit Range/Performance

P0462 Fuel Level Sensor Circuit Low Input

P0463 Fuel Level Sensor Circuit High Input

P0464 Fuel Level Sensor Circuit Intermittent
 
Last edited by a moderator:
Go to Autozone or somewhere else where they will pull the code for free before you know yourself out checking your wires. You may save yourself LOTS or wasted time...
 
I"ve already had the CEL cleared, and it hasn't popped up again (I had it cleared yesterday afternoon at lunch, and it didn't come back on during my drive home, about 15-20 mins). Are CELs stored in memory?
 
You said the magic word....solder. You should use good crimp connections, not solder. You might have a cold joint which will have a high level of resistance. Soldered joints on flexible wire also tend to degrade over time. Vibration induced stress can cause crystalization and cracking of the metal matrix [lead and antimony] which again will increase resistance or form an open circuit. Solder is good for rigid joints but not where there will be flex in the wire.
 
Well, Ford recommends using solder to join two wires, and I did all my wires the recommended Ford way...maybe that was a bad thing. But no cold joints here...I make sure of that.



I've got the wire to redo all of my connections, but I'd rather not. Jeeze I need to get a daily driver real bad...
 
Tiger,

Did you solder with rosin core or acid core solder? You should never use acid core solder for electical connections, but I'm sure you already know that.



The easiest way to find out if the wire is causing the problem is to measure it's resistance with an volt/ohm meter. The wire may have a small break and that is causing the high resistance. You could replace the wire with a larger gauge wire or use two strands of the same wire.



Also, is the fuel sending unit the same unit that is normally installed in the regular gas tank, or is it a universal sending unit? The new unit may have improper voltage polarity or improper resistance. I have swapped fuel gauges on cars and had the gauge read empty when full and full when empty, because they reversed the resistance values?



But I don't think your problem is necessarily electrical. The Sport Trac fuel tank is supposed to have a slight vaccum when operating. If you do not have a vaccum in your replacement tank or it is not vented properly, that may be causing the CEL.



...Rich
 
I'll be sure to check resistance this weekend.



I used the stock sending unit, which leads me to think the problem is with my additions.



I think I'm just going to buy an aftermarket fuel gauge sender, and an appropriate aftermarket fuel gauge. I was planning on doing so in the future anyhow...so I guess the future is now.
 
Tiger, I think you are dealing with an issue in the fuel level sensor itself, and how it relates to your new tank.



The impedence of copper wire is approx 1 ohm per 1000 feet. I don't think this is playing into your problem.



cheers,

 

Latest posts

Top