Shorted to Ground electrical problem????? or something worse

[xsplatz]

I have a 2000 ford explorer, 5.0L V8. I recently did a major engine build, Xtreme Energy cam, AFR heads, MSD, 2800 Stall converter, Walbro 255 fuel pump, flex-a-lite fan. custom True Dual exhaust, ect.

I also have an XCAL3 from James and am Innovative Motorsports LC-1 Air Fuel gauge/data logger.

For about 4 weeks the truck ran and i was datalogging and slowly buildng up the tune for my truck. About 2 weeks ago i finished one of my 2nd gear pulls and then headed home. Half way there i saw as my A/F gauge began to fluctuate from 8-14 and then red error light began to flash. I pulled over, turned the truck off and then started it back up. The gauge went through the start up and was fine again

I began to drive home. This time when i pulled in the drive way the Gauge was all the way down on 8 and the Red error light was completely off. Because i didn't want to damage the sensor i didnt drive the truck, but checked all my grounds to make sure i didnt burn a wire. As i was testing things i realized that the fuse i had tapped into for the ignition was shorted to ground. But no fuses were blown the truck would start up fine. So i began to check all of the fuses and relays. none of which were blown or not working.

Now as i wanted to go further into the engine and harness to find out what had shorted i began to remove the intake to open up the harness. As i disconnected the negativ battery cable i saw the juice arch from the negative cable to the battery stud as i was taking it off. In my mind that was a clue that something was shorted to ground. I unplugged the computer in the engine bay and the harness connection to the trans and to the relay box to completely isolate the harness from anything. I also removed the positive batter cable going to the relay box and the alt connection to the relay box to try and isolate the problem. I removed every Accessory that i had connected to the battery or any power source. I then reconnected the negaive cable to see if i had gotten any closer. .. again i was getting a short to ground on all of the fuses. I disconnected the the MSD coil packs and when the negative battery cable was still attached to the battery and i could hear the juice arching to ground on those as i removed them. I then pulled out my fluke multimeter to test where the current was.

This is where i became completely stumped. Right now i cleaned every gound connection in the engine bay. The only thing that is hooked up is the negative cable to the battery/chassie and the positive batter cable which isnt even attached to the starter anymore. And if i take the multi meter and put the positive probe against the positive terminal and then touch the negative probe against any part of the engine, valve covers, headers, fuel rail, metal frame of alt, i end up picking up a positive volatage of +12.40 where the battery +12.40 As i have nothing connected i have no idea where this charge is comming from.. any help or a direction would be helpful.

One crazy thing that i thought was my eyes at 3 am was that when i probed the metal bracket holding the flex a lite fan n place was a higher reading of +12.78. No idea how to explain that..

Besides a possible ignition switch short i dont know what else it could be. Since nothing should be getting juice when the battery is connected except the positive cable.

thanks. Getting tired of long nights in the garage with the multi meter and constant testing.

 

[CrownRoyalRacing]

The negative battery cable should be also grounded to the chassis. The engine is mounted to the chassis and therfore provides a grounding point from any point of the engine. The charge you are seeing is from the battery.....not the engine. The engine components are just providing you a ground to see the battery voltage. If the voltage was -12.40 vdc with the red lead on the power source, then you would have a problem.

 

[xsplatz]

The. Negative cable is connected to the chassie and to the bottom end. Something is somehow leaking voltage into the block or the negative cable is bad but I am running out of things to test and connections to pull

 

[CrownRoyalRacing]

That's right......what you are reading is normal. To get a voltage reading on a voltmeter....you must have a power source and a ground. The voltage you are seeing is the battery voltage, and the engine is providing you the ground. Now if you were putting the red lead on the engine, and the black lead on the negative battery terminal and getting voltage, that would be bad!!

Unless I missed something above.....what you are seeing is normal.

 

[xsplatz]

Crown. Thanks for the help. I forgot to mention if I spin it around. Red probe on engine black on positive terminal I am getting same volts but as a "-" negative. I also should have mentioned that I have a brand new yellow top and after the LC-1 stopped working my battery was drained down to barely hearing a click with the key turned no lights comming on.

Also if I probe any of my ground connections on the chassie they show a significant amount of voltage running through them. Even the lc-1 grounds ok the frame show the positive 12v

 

[CrownRoyalRacing]

Almost all of the power wires in a car are fuse protected, so if one was shorted to gnd, it would blow a fuse. I am curious how you are probing the ground connections. The best way would be to ring continuity (ohms check.....not voltage) between the post and the negative terminal of the battery. They should all be under 2-3 ohms. Then I would remove the postive battery post and ring continuity from that post to ground. It should be open or a high resistance.

 

[CrownRoyalRacing]

Who wired in the LC-1? I'm thinking that it may have drained your battery. You might want to see how it is wired.......

 

[xsplatz]

The lc-1 was disconnected from power right after I realized the grounds were compromised. It was after I pulled out the positive lead to the lc-1 that the battery drained. I will do an ohms check as soon as I get homefrom work tonight. And I will post the ohms. If there is anything else I should check please let me know I greatly appreciate it. I have been worried that there was a bad short and didn't want to drive the truck for the last month becuase I was afraid it would short the pc

 

[CrownRoyalRacing]

Is the LC-1 wired directly to your battery? I would check how that wire is stowed or remove it from where you tired in to get the power. If the battery stops draining after that, you know there's a problem with that wire.

 

[xsplatz]

The wire was tappe into the number 13 fuse or 14 fuse in the engine bay fuse box. When we tested it it was an ignition "on" fuse, this way there wasn't constant power to it. The fuse was the one with o2 sensors cam position sensor and something for the tranny.

 

[CrownRoyalRacing]

That shouldn't be the problem then.......I'm not the best car mechanic, but I make a living on electronics.......so I would do those resistance/continuity checks and see where you stand.

 

[xsplatz]

Thanks again for all your help. I'm heading home now and will test the ohms and repost. The only thing that I don't get is that the positive battery cable is only attached to the battery nothing else only the neg is connected to the bat chasei and engine block

 

[CrownRoyalRacing]

According to Dr. Haynes......there are 2 different ways that it could be. ONE......2 wires off of the positive......one to the starter relay.....and the other to the starter solenoid. TWO........one wire off of the positive that eventually splices down to 3 fused wires.......2 of the fused wires (gray) are linked fail-safes.....if one fuse blows (no fuse value given), you still have power thru (both lead to the same spot at the Generator/Voltage Regulator).......the other is a black wire with 15A fuse that goes to a different postion at the Generator/Voltage Regulator. That's all the help I can give you there........


That's for 1995-1999 Exploder/Mountaineer ------later models similar.

So that might not be how yours is wired.....but that's all it shows in the manual.

 

[xsplatz]

Ok so by the time I got home I figured I would begin testing from the beginning of out convo.

So I hooked up the battery cables and ran in side for a quick bight to eat and in 30 minutes the Volts in the battery dropped 0.09 volts.

“For the 2nd statement you made by putting the red lead on the engine, and the black lead on the negative battery terminal and getting voltage, that would be bad!!”

So I hooked it up that way. Black on neg and red to probe the areas. If I connect it to the engine I am getting 0 volts, but If I move the probe from the engine to the metal radiator I am getting “-0.330” V.

Testing with the same set up, where the upper radiator hose attaches to the thermostat on the intake manifold it was spiking and showing “0.060”

Then the metal Ac lines carrying the Freon from the condenser tower going to AC condenser was showing “+ 0.175” V in them

The AC condenser in front of Radiator was showing ”+ 0.182” V when probed

Just for the hell of it I wanted to test the coolant and see if there was anything in there. I buried the probe tip into the reservoir next to the washer fluid. The Coolant had a voltage of “-0.114

So thinking I was loosing it I kept testing the same spots and they all showed the same results +/- 0.005

even at the bolts holding the coil packs to the mounting bracket I am getting a “-0.116” Most likely because the bracket is anchored into the upper intake manifold by 2 bolts which are probably picking it up from the coolant.

All this will happen if the positive battery cable is removed and the negative is just attached or if they are both hooked up..

I didn’t get a chance to do the ohms testing as it got to late…. but I will try tomorrow

If there are any ideas on what might be causing this or where to start looking please let me know.

thanks

 

[Cobraguy]

I am curious how you are probing the ground connections. The best way would be to ring continuity (ohms check.....not voltage) between the post and the negative terminal of the battery. They should all be under 2-3 ohms.

That is probably not the best testing procedure for this. You can have a very poor automotive connection that shows very little resistance. (i.e. one strand of a wire would show little resistance on an ohm meter...but be a horrible connection to have) In this case, most would recommend a voltage drop test.

This sure sounds to me like it's missing a ground somewhere and trying to feed back any way/where it can.

 

[budwich]

Not really sure what problem you are trying to solve???? your poor understanding of electrical operations or a poor connection???? to some third party instrumentation that you connected into the system in "some manner".

 

[xsplatz]

Would be a constant battery drain with the wiring harness and whole fuse pannel eliminated from the possibilities. So something that is pulling voltage from the battery or something shorted after a major engine rebuild. The after market instrumentation was cited for the reason I found the short/battery drain in the first place.

Most forums are there because people have questioa about something they don't know something about. Hence the amount of details to try to shine some light on what could be wrong

 

[CrownRoyalRacing]

"If you suspect that there is a voltage drain on the battery while the vehicle is sitting in the driveway, remove the battery positive terminal, install a test light between the battery terminal and the cable (series connection) and observe the test light. If the light is BRIGHTLY illuminated, there is a circuit that continues to be active. NOTE: the test light will glow dimly because of the parasitic drain of the ECM, radio, clock, etc.... Carefully remove the fuses one-by-one that govern accessories such as radio, blower motor, trunk lights, etc. until the test light goes out. Trace the short circuit in the particular fused circuit and repair problem. Recheck the electrical system as described."

That is straight out of the Haynes manual. It's pretty basic, but will at least narrow the trouble system down for you. Good luck!!

 

[Verno]

Ok, I went back to your first post and re-read it. I'm not a wizard or expert when it comes to all the aftermarket stuff you've added and I won't get into asking why at this juncture...
In your initial post I quote you "I began to drive home. This time when i pulled in the drive way the Gauge was all the way down on 8 and the Red error light was completely off. Because i didn't want to damage the sensor i didnt drive the truck, but checked all my grounds to make sure i didnt burn a wire. As i was testing things i realized that the fuse i had tapped into for the ignition was shorted to ground. But no fuses were blown the truck would start up fine. So i began to check all of the fuses and relays. none of which were blown or not working. "
#1. Stop checking for 12VDC your not getting anywhere the way you're testing.
#2 How did you determine the "fuse" you tapped into was shorted to ground but not blown???
#3 Fuses can be tested two ways; either by testing voltage (i.e. 12vdc in and 12vdc out) or resistance (good fuse will be virtually zero while a bad fuse will be open or infinity) Remember if you are doing resistance testing, all power needs to be shut off first.
As a side note, I get a slight arc when I disconnect the neg cable on my Gen I because there is power to the under hood light!

 

[xsplatz]

I got that part the problem that remains is that I have completely disconnected the battery connection going to the computer, and both fuse boxes to eliminate a parasitic drain from the accessories or open relay.