S10 LS V8 Swap

I left a spark plug wire unhooked and started attempted to start the truck. now no lights come on or anything.

If I unhook the battery negative and using a DVOM meter black lead on the negative battery terminal, red lead on fuses in the fuse box under the hood I can get a battery voltage reading of 12.16-12.30 on all fuses.

If I hook the battery negative cable up to the battery and do the same. on the fuses I get a reading on the DVOM meter from the fuses of: 3.962-4.000

Ive checked all the relays, and they are good. I'm not sure what to be looking for. Ive had this truck running, and just got the computer back from being reflashed and now since that mistake, I cant get it running yet.

I had ordered a Powerprobe ect 3000 but it was defective out of the box, so I sent it back. any help advice or tips would be greatly appreciated.

I would have to say clean your battery connections and the cable connections at fuse block. Apply a lite coat of dielectric grease on terminal connections and put it back together and see if that does the trick. Just the way it sounds it's a battery connection issue.

Are there any high amp fuses or fusible links between the battery and the fuse box?

I forgot to mention no dash lights , no anything.

There is a fusible link, at the battery, it looks like a wire and says fusible link,

but when I test it with a DVOM for continuity it checks out, it doesn't seem bad, but could it still be?

when I went to crank it I heard a popping noise, so I wonder if a ground wire has popped off a connection somewhere,

its on a 99 s10, and there is suppose to be a main fuse somewhere on the fender in some of the diagrams ive seen, but I cannot relocate it. I'm not sure if a main fuse was just made on the 4 cylinder engines from the factory.

Seems to me you're getting a voltage drop between the battery and the fuse box. That fusable link has to carry a lot of current. Just because it has continuity with an ohm meter doesn't mean it will carry current. Try to narrow down your voltage drop.

how would you go about doing that. I've never done a voltage drop test before. I wouldn't know where to start.

With 4 v fuse to B- you should have over 8 v volt drop from B+ to fuse. Take voltage measurements along the B+ to fuse circuit to find where that 8 v drop is happening. How I'd test this one is first measure voltage from the + battery post to an always on fuse, which isn't fed from another fuse, just to confirm there really is an 8 v drop. Then leaving the red lead on the battery post move the black lead back toward the battery until I find the point where I measure 0 v instead of 8 v. The problem is between that spot I measure 0 v and the last place I measured 8 v.

You have much of the info you need already, based on your voltage test at the fuse box. Just keep doing that measurement, working your way back toward the positive battery terminal.

I'm not sure where you took the first measurement, was it on one of the fuses itself? There should be a power feed from the battery to the fuse box. Check the voltage there. If that feed coming to the fuse box from the battery is still 4v then your problem is between the battery and the fuse box.

Matt gave you some good instruction about voltage drop which is exactly what I was referring to. For someone new to electrical troubleshooting, voltage drop can sometimes be a little tough to wrap your head around--i.e. measuring voltage on the same side of the battery. Voltage drop occurs any time you have current flowing across a resistance. That resistance can be a regular load, it can be a resistor, it can be corrosion, or even a fusible link that burned all but one small strand of wire. When you disconnected the battery negative cable you stopped all current flow through the electrical system. That's why you measured 12v in the fuse box. Once you connected the battery negative cable, the current started flowing and the voltage drop is happening across the resistance somewhere. You just need to find where.

Paul (ScannerDanner) has lots of videos out on YouTube about voltage drop but the key is "no current flow, no voltage drop."

Just from your description of symptoms I think you have a resistance between the positive battery post and the fuse box. Could be the battery terminal, could be the fusible link, could be something in the fuse box. Doing the voltage drop test as Matt described will help you find it.

I took the positive battery cable off the battery. I left the negative side hooked up. I took a jumper wire and put it on the positive battery post, and then to the positive side of the fuse block, and all the lights come on, and if I turn the key the gauges like the fuel gauge will come on. I haven't tried to start it cause I still don't know what the problem is.

but like I said if I hook the battery up bypassing the battery cable I have in there, the lights on the outside will come on, even with the key off.

what is your opinion on what could possibly be the problem.

It would be helpful for you to follow the suggestions already given. You gave us enough in the first post to figure out that you have resistance in the cable between the positive battery post and the fuse box. If you put a jumper wire in from the positive battery post to the fuse box, and your lights come on normally, that even further confirms it. You can try and start it as long as the wire you're using as a jumper is big enough to carry the current. Remember, though, that the jumper wire has no fusible link so if there is an overcurrent somewhere that burned that fusible link then you could melt something.

If I had to take a guess here, I'd say the fusible link blew, at least partially, for some reason. I doubt the ignition coil had anything to do with it.

First, before you do any testing you need to have a good battery. No tests will be accurate with a low battery. That's step one.

Then, with the battery hooked up normally, key ON, and without your jumper wire installed, take a voltage measurement with one lead on the center of the POSITIVE battery post (not the cable terminal but the center of the POSITIVE battery post.) Put the other lead on the lug at the fuse box where the cable from the battery connects to the fuse box. What is the voltage measurement there? If everything is good it should be close to 0v. If you have resistance in that cable you will see some voltage. What voltage do you see?

so the reading of the battery is 12.48

if I take one lead of the DVOM and touch the center of the postive battery terminal, and the other lead and touch where the positive side goes in the fuse box this is the reading my DVOM gives me.

it reads OL/ -7.48 (negative 7.48)

NinetyNineChevy wrote: so the reading of the battery is 12.48

if I take one lead of the DVOM and touch the center of the postive battery terminal, and the other lead and touch where the positive side goes in the fuse box this is the reading my DVOM gives me.

it reads OL/ -7.48 (negative 7.48)

Perfect! That is called a voltage drop. It's negative only because of the polarity of your leads. If you swap the leads and do the test again it will be positive, so just as Matt T above said earlier, you have nearly 8v of voltage drop somewhere along that cable.

Can you move your test leads up that cable and check it closer to the battery terminal so as to more narrowly isolate where the drop is occurring? Maybe test with one lead before the fusible link and one lead just after the fusible link? You can also do the same type of test between the battery post and the battery cable terminal. If you see 0v of drop then you know the connection is good.

The key to a voltage drop test, however, is to have the key ON so that you have current flowing on that wire in order to see the voltage drop. If you were to do the same test with the key off you'd see 0v of drop. So, you always need current flow to find a voltage drop.

so I put the red lead on the positive side of the battery. the cable splits from the positive battery cable to a fusible link and then to the fuse box, over to the battery.

If I put the red lead on the positive side of the battery and touch the positive wire on the fuse box the meter will read 8.48/OL/11.48

if I touch the wires where they branch off, reading from the battery to those wires, the reading on the DVOM is 11.48, if I touch on opposite sides of the fusible link the DVOM reads 11.48

If you touch the battery post and then the cable terminal do you get close to 0v? That would indicate a good connection at the battery cable. Then just work your way down the cable til you find where the drop starts.

so what would the DVOM read if its dropping?

I took a jumper wire with a fusible link I made with a 15 amp fuse, and put in place of the fusible link that goes from the back of the alternator, to the positive battery connections, and turned the key on, and nothing, so I don't think its the fusible link.

if I leave the positive terminal hooked up to the post, and touch the red lead to the center of the battery post, and touch the black lead on the battery cable.

the DVOM reading is 9.04 VDC.

Wait, why are we now talking about the alternator? Besides, a 15A fuse is not the same as fusible link that's probably rated at 100A or so. That 15A fuse will blow instantly as soon as you start the vehicle and the alternator starts charging the battery.

We already determined there is a problem in the cable between the positive battery post and the fuse box. None of us are there to fix it for you. You're going to have to find it. I thought you said there was a fusible link between the battery and the fuse box. If there's no fusible link between the battery and the fuse box then it's just a problem with the cable between the battery and the fuse box. It could just be your battery terminal or whatever attaches that fuse box wire to the battery terminal.

Again, this is narrowed down to a bad positive cable between the battery and the fuse box. How about some photos?

so I will post photos if I can upload them from my phone.

but I did cut out the battery cable, ( I had ran 0 gauge wire, I was going to run the battery in the truck bed but didn't, cause I ended up having enough room in the stock location).

SO I cut the wire out I had ran for the positive side of the battery, and hooked it back up to the battery, and everything cut back on.

so either one end of the cable was bad, or where I had ran the positive cable under the radiator core support, it was touching the metal.

I need to hook up the fusible link back up to the battery, so this wont happen again.

any advice on that. I have a spare fusible link box, and the stock one that was for the s10.

and btw, on a 4.8 liter gmc, for some reason they have a fusible link between the alternator and the battery. its in its own box, I'll post photos if the forum will allow it from my phone.

until I get a new cable, and the fusible link hooked up like its suppose to be, Im not going to try to start it. but with the key on everything is coming back on , like it was before.

So I can get the truck to run. But the battery light and dash lights will stay on. Even with the key out. I tried connecting the fusible link like the diagram. And the dash lights come on even with the key out. The battery light on the dash is on too. I just wonder since the positive cable was messed up. if the negative battery cable I had in there is messed up. and causing it not to be grounded. making the lights and battery light stay on. I can start the truck, turning the key over. but the lights stay on even with the key out. like I said.

This is the diagram