Electrical question before i send to mechanic.

[Dano!]

way back my electrical stuff when concerning my fuel sending unit / fuel pump pooped on me. what i had to do was splice a second ground into the wire coming out of the sending unit. my fuel pump works as it should but i ever since then my battery drains itself. my temporary solution to that was to install a battery disconnect switch. but popping the hood every time i go somewhere to connect or disconnect my battery is getting old.
i talked to a mechanic today and they would like to try and figure out whats going on but understandably cant quote me any kind of price. i myself have some basic electrical experience and i can read a wire diagram. but for the life of me i cant figure out where my issue is. i tried tracing the original ground but it dissapears back into the contraption behind the transmission. (i don't know what it's called)
the whole reason i just spliced a second ground vs re routing the sending unit ground was i did not know if any other system used that ground along the way. i have always felt the mechanic route was a last resort but i just have a feeling I'm going to pay big bucks for something that is probably a simple fix.
is there any other systems that use that grounding wire or the ground that the wire eventually ends up at? did i create a separate circuit when i created the second ground? i don't get any check engine lights or anything, no flickering lights, nothing changed when i made this modification except the battery started draining itself. all the problems i had before stayed the same. which to my knowledge was my speedo doesn't work and the ash tray plug in doesn't work.
any ideas or methods of elimination would be helpful and i would be more than willing to put a six pack in your fridge if you actually help me figure this out. hell if someone lives close enough id pay for you to come up here and help me figure this out. (Lemoore CA)
anything would be a great help.

 

[carboncanyon]

Disconnect the ground wire going to the battery.

Take your 12v test light and clip the gator clip to the wire you just disconnected, and clamp the probe tip to the battery post. (Your test light becomes a jumper to reconnect the ground cable to the battery.

If the light bulb glows bright, you have a big draw. If it glows dim, you have a small draw.

Now start pulling fuses. 1 at a time until your test light stops glowing, or reduces its glow greatly.

Look in your wire diagrams and see what fuse you just pulled out. Your trouble is in that circuit.

Dont try to start your rig, or even turn on any accessories, in fact, leave the keys on the floor. If you put too big a demand on your test light, you will burn it out.

Dont forget to rule out things like hood light and dome light when the doors are open, those will make your test light glow brightly unless you turn them off during your test. (unless your problem is in those actual circuits, like your hood light not turning off when closed).

 

[Dano!]

Disconnect the ground wire going to the battery.

just to be clear, your not talking about the whole ground cable, your just talking about the wire i routed to the battery. right?

 

[carboncanyon]

No. I mean the whole shooting match. The big gnarly black cable that ties your entire electrical system to the battery. Disconnect it, and use your test light to become a "jumper" wire between the battery, and your main ground wire.

You want EVERYTHING going thru your test light in order to perform the above test. But again, you want to make sure everything is OFF, because your looking for a drain that happens with the engine off and you in the house asleep.

 

[Dano!]

alright. that actually makes sense to me. first thing tomorrow i will buy the 12v test light and i will post what i find. thank you.

 

[carboncanyon]

make sure its a regular light bulb, and not an LED or anything fancy like that.

The LED lights dont "glow". They are either ON or OFF, and they will turn ON with almost no load!

The regular light bulb will glow very dim for a small draw, and as your electrical draw gets bigger, the bulb will grow brighter and brighter until you overload it and it blows.

You can do the same test with an amp meter, but the old lightbulb trick is alot easier I think.

Adding a new ground wire shouldnt have caused your problem, unless its a circuit that uses the computer to ground the wire, and your bypassing the computer with a full time ground, which results in the item you grounded always being "on" even when the truck is shut off. I dont have a wire diagram in front of me, so cant tell you if the sender circuit is switched hot, or switched ground.

 

[Dano!]

Closing out the Thread

Thanks again,

I did this and found that one of my relays were stuck open. it was very strait forward and helped me a ton. thank you for your advice.

I swapped the relay and was happy that i could take my electrical toggle out. no more foolishness.

- Dano