voltage drop on acceleration

[Mbrooks420]

Don't drive it without the battery connected. The voltage went up since there was no where for any juice to go. Get your alt/battery tested at an auto place.

 

[storlied]

Anytime I bring either in, they test good.

Are there any common grounds on the 2nd gens that go bad?

 

[BrooklynBay]

Never disconnect the battery on a modern fuel injected vehicle while the engine is running. The high voltage could damage the computer or other sensitive electronics.

 

[storlied]

I made some progress in my investigation.. I had my hands on a voltmeter thing again today... tried something Gavin told me to do.. I was checking the output voltage from the alternator but instead of using the battery ground, I used the alternator housing.. at this point I'm pretty excited.. I'm getting a good 14.8v or so... alright good.. the alternator is doing it's job just fine.... here's the catch though... I put the ground (for the voltmeter) on the negative post of the battery, and the reading gives me the crappy 13.0-13.2... I'm thinking Wtf.. I try putting it on the body... same low reading.. and for the hell of it.. I tried the frame, same thing.. and even that ground strap on the firewall.. same thing... so I tried something a little weird.. (well, typical for me anyways..lol) I put a jumper cable on my negative battery post... and put the other end on my engine.. =\ and what do I get? A good 14.8v!!! Both from the voltmeter and my radar detector... also.. the oil pressure gauge stopped shaking and moving around... turned everything on, and still a good voltage, even went up a little bit after I reved. Keep in mind I didn't drive like this, so I don't know if this solves the problem completely. If it does, the only thing left is the overheating issue.. Gavin mentioned no electrical issue could cause an overheat.

Neg batt to alt will fix this issue, but there's still an issue beyond it I want to take care of..
So.. pretty much what I have here is the engine is a good ground, and the body And frame are not very good.. which I don't understand... now to the work... Which grounds should I be looking at? I know about the two on each side of the frame, and the one on the firewall.. question is.. what does the firewall one go to? And I'm going to be removing the battery to body ground wire and grounding it to the alternator... besides that wire, there's another one on the negative terminal, where does that go? I can't seem to follow it well.

 

[BrooklynBay]

It sounds like there is corrosion on the negative battery cable at the point where the cable connects to the body. Trace this wire, and clean the connnection.

 

[storlied]

It's clean, I can test it Anywhere on the body and frame and get a volt worth of loss.

 

[Mbrooks420]

Run a new wire to the battery, and run a fresh ground from the battery to the frame.

 

[Mbrooks420]

What's the resistance between the negative battery post, and the end of the wire where it bolts to the frame?

 

[BrooklynBay]

I agree. Replace that battery wire. I'm sure that it's causing all of these problems.

 

[storlied]

I don't know how to test resistance, or even understand it. All I do know from voltage testing is that the frame, tested on a frame rail and even the top bolt stub of the shock..along with any exposed metal on the body are bad grounds. While the engine as a ground lets everything get all the power it needs. I need to figure out which ground is bad... but I only know of the two under the front doors (body to frame) and a ground strap on the firewall that I have no idea where it goes... I also don't know where the thick ground wire from the battery goes. (obviously not talking about the battery to body wire) I've read the engine is electrically isolated from the frame and body, what does that mean? Would it harm anything to ground the battery and body to the engine? How about killing the batt to body ground and making the batt go straight to engine? (I'd prefer not to because all of my accessories are grounded on the fender bolts, but I don't know if it's a good idea to ground the body to the engine?)

I think my situation is close with a few things from this thread:
http://www.explorerforum.com/forums/showthread.php?t=99071&highlight=v8+voltage+ground

Something about all of this confuses me, I always thought everything ended up grounding at the frame... this is odd considering the frame (along with the body) is a bad ground...

A few other resources for reference:
http://www.explorerforum.com/forums/showthread.php?t=216325&highlight=v8+voltage+ground
http://www.explorerforum.com/forums/showthread.php?t=75915&highlight=v8+voltage+ground
http://www.explorerforum.com/forums/showthread.php?p=1717285#post1717285


I'm leaning toward this being a batt to engine factory ground issue... it just throws me off since I thought frame is the end ground... tomorrow I'm going to go hunt down this ground from the pictures posted by 410fortune, I'm sure I'm going to find an issue... if I don't.. well a wire from the batt - post to the alternator bolt (closest to the battery) will be the fix.. that Should ground the body out.. and Should ground the frame since the side straps look good still...

 

[Mbrooks420]

The cab and the body are excellent grounds. Your cab/frame have a bad connection to the battery. All grounds flow to the neg battery terminal. A bottleneck here would mess it all up. You test resistance using the Ohms setting on the multimeter. You probe the negative terminal, and the ground/wire you are checking. This number is resistance. The higher the resistance, the harder it is for the electricity to pass through resulting in a poor ground.

 

[storlied]

The connection that comes straight off the battery neg to the body is clean and good... there's another ground somewhere that's bad. I've tested using jumper cables and no matter where on the frame I put it, it gave me crappy results.. the Only place that let me get the same reading as the alternator was the engine.

 

[Mbrooks420]

The connection that comes straight off the battery neg to the body is clean and good... there's another ground somewhere that's bad. I've tested using jumper cables and no matter where on the frame I put it, it gave me crappy results.. the Only place that let me get the same reading as the alternator was the engine.

That proves my point. IF that were a good ground, you would get the same voltage grounding to the frame, as you did testing across the battery terminals. Just because the terminal is clean, and the grounding spot is rust free doesn't mean the wire isn't bad under the insulation. Do a search, the battery cables going bad is a common problem Explorers have always had. Replace, or test the negative cable.

 

[BrooklynBay]

Any auto parts store will have # 4 or # 2 gauge black cable with a precrimped end, and a battery terminal end.

 

[storlied]

I ended up getting one of those 'starter to battery' (4g) black cables and connected it on the bolt where the ground strap is on the firewall, and ran the other end on one of the alternator bolts. Voltage is a good 14.8+, my oil gauge doesn't move all over the place.. and this one I really like.. my dash lights are brighter than they ever have been.. here's the odd part though.. my cooling problem.. is Gone! Which is good, but weird. Problem solved.

I couldn't keep tracing that huge ground that wraps around the engine, I kept losing it on the passenger side.. and I couldn't see what was going on with the firewall ground strap... each end was frayed a little bit though.

I hope someone can use this thread if they have this problem.
Thanks for all the help and info everyone.
I'm going to end up replacing all the ground straps with these cables.

 

[Mbrooks420]

Maybe your truck wasn't overheating at all. Electronic gauges are sensitive to voltage changes. It was probably being messed up just like the oil pressure gauge.

 

[BrooklynBay]

Thanks for the update!

 

[storlied]

Small update, alternator bolt isn't the best ground. I changed it to the bolt closest to the front of the truck that holds the upper intake down. (to the right of the throttlebody)

As for the gauges.. I really don't know.. that's just so weird... check gage light even came on one time when it was getting too 'hot'.
Bad grounds can cause some crazy weird issues.

 

[techieman33]

Small update, alternator bolt isn't the best ground. I changed it to the bolt closest to the front of the truck that holds the upper intake down. (to the right of the throttlebody)

As for the gauges.. I really don't know.. that's just so weird... check gage light even came on one time when it was getting too 'hot'.
Bad grounds can cause some crazy weird issues.

Be very careful when messing with the upper intake, that bolt you used for your ground probably wasn't the best place. That ear on the intake is very easy to break off so I would mess with that bolt as little as possible.

 

[storlied]

Are we talking about the same thing?