Electrical problem truck won't start

[65-72 chevytoys]

I just replaced the battery and still won't start, so I started to trace the wiring around the engine compartment. 12R from Battery to starter is good. 12B from Battery to engine block is good. I could not see the starter real well so I went the other direction. HEI Bat terminal has a 20Y that is disconnected at the starter terminal. I have been reading the FAQ section on HEI conversions and noticed that it needs a heavy guage wire that goes from the HEI bat terminal to the fuse box ignition unfused with a 30A inline fuse correct? I don't think there is a positive connection that goes from the battery to the fuse box?? Also what does the yellow wire connect to and what about the orange/purple wire from the fuse box to the starter terminal??

[jayharrell]

heres a diagram i put together for my 455 with an HEI and internall regulated Alt. Might help if you have the origonal diagram from the FAQ.

[jayharrell]

I rewired my tach for the HEI where the oil pressure goes through the fire wall pull because my 455 has a hard line just going through the fire wall it self.

[old Chevy guy]

That yellow wire from the starter goes to the coil on a points ignition to prevent voltage drop to the coil while cranking the engine,not needed with hei .The big orange,used to be purple,wire on the small post closest to the block comes from the ignition switch to trip the solinoid and make the starter go. you did'nt say whether she turns over or not,Im guessing not if you changed the battery. If that purple wire is disconected somewhere the starter wont turn over.Is it an automatic? If so check the neutral safety switch,its inline in that purple wire under the dash.If you can see it you can try jumping the Purple terminal to the battery cable post on the starter with a screwdriver,making sure your all in neutral of course. I sarted my camaro like that all the time when there was a bad conection somewhere.

[Longhorn Man]

we need the basic info.
Do the headlights come on?
when you turn the key to on, will the heater blow, or turn signals work?
When you twist the key to start, do you hear a click... does the brake light in the fuel guage come on?

[jayharrell]

yeah.. sorry i didn't KISS it *keep it simple stuipid*. Probably a nuetral safety switch. Mine is bypassed. Didn't even think.

[65-72 chevytoys]

Thanks for the help guys. I will go check tonight after work and get some more info. But after checking the original diagram it seemd odd that the yellow wire that is no longer needed was connected to the Battery terminal on the HEI and hanging loose on the other end. I think this is the problem, no power to the iginion or coil.

Jay after looking at your modified diagram for the HEI swap the orange/purple wire should now connect to the power terminal on the HEI correct?

Thanks for the help so far, I will take a look after work.

[jayharrell]

Right.. the one that used to go to the coil now goes right to the BATT on the HEI.

Man you jinxed me. After i got done with the PC last night i figured i'd start the ol girl up. Same probablem as you. Only my Tach was reading rull tilt 5krpm. Way too wierd that it happened.

[65-72 chevytoys]

Originally Posted by Longhorn Man

we need the basic info.
Do the headlights come on?
when you turn the key to on, will the heater blow, or turn signals work?
When you twist the key to start, do you hear a click... does the brake light in the fuel guage come on?

Update: I have no power to anything headlights, turn signals, or anything.
I did check all the fuses and they are good. Also the PO upgraded to HEI but left the external alt. and volt regulator.

I also took some pics to help with what I am looking at.

pics are the following:
1. external reg. alt.
2. wiring at the battery
3. The yellow wire that is connected to the HEI battery terminal
4. Wiring to the starter solinoid.

As you can see on the solinoid. The heavy guage wire coming from the battery is connected to the top post.
I looks like the purple wire is connected to the right post, and the yellow wire is disconnected???

[jayharrell]

are the bat cables on the rigth terminal?? + and -. With no power to anything anywhere thats just wierd.

You can take a screw driver or pair of plyers and jump the main terminal on the starter to the solinoid, that'll show if your starter is working.

I would think other then that is your key switch or under dash wiring.

[Longhorn Man]

you are looking in the wrong areas.
No power to the truck at all... this means it isn't getting from the battery to the fuse box.

Looking at this photo is kinda difficult... do you have a red cable on the negitive, and black on the positive, or do you have a backwards polarity battery?
What ever it is, there should be a red wire going from the positive post, across the core support, to the voltage regulator area by the horn, on the back side of the dvr headlight. There is also *supposed* to be a fuseable link in that wire, just off the battery.
If I am looking at that photo right, the positive is the red, and that wire is just hanging down towards the metal fenderwell, and then going actross the core support.
If I am seeing it right, then that is probably your problem. I'm thinking the cable/bolt bumped the fenderwell, which is a ground, and burned out the fuseable link.
Verify this, by probing for power in that yellow but connector. If it is dead, then the link in the pigtail there is fried.
If you have power there, then follow that wire across the core support probing it here and there, untill you find where you drop power.
I bet it is dead at the crimp on if that power wire is in fact just hanging there like I think it is.

[72swb_327stroker_?]

Originally Posted by Longhorn Man

you are looking in the wrong areas.
No power to the truck at all... this means it isn't getting from the battery to the fuse box.

Looking at this photo is kinda difficult... do you have a red cable on the negitive, and black on the positive, or do you have a backwards polarity battery?
What ever it is, there should be a red wire going from the positive post, across the core support, to the voltage regulator area by the horn, on the back side of the dvr headlight. There is also *supposed* to be a fuseable link in that wire, just off the battery.
If I am looking at that photo right, the positive is the red, and that wire is just hanging down towards the metal fenderwell, and then going actross the core support.
If I am seeing it right, then that is probably your problem. I'm thinking the cable/bolt bumped the fenderwell, which is a ground, and burned out the fuseable link.
Verify this, by probing for power in that yellow but connector. If it is dead, then the link in the pigtail there is fried.
If you have power there, then follow that wire across the core support probing it here and there, untill you find where you drop power.
I bet it is dead at the crimp on if that power wire is in fact just hanging there like I think it is.

i saw that bolt hanging there and thought exactly that... then i scroll down to see you nailin it! damn your good

[jayharrell]

hey now... i called it before longhorn, i'll give him respect for being who he is, but hey now....



srry, didn't see the bolt. no power for sure there. *bows to longhorn* being from austin i should bow more often to someone named longhorn.

[Longhorn Man]

looking at that photo again, i think I see where the fuseable link is burned in the pic!

[VetteVet]

Originally Posted by 65-72 chevytoys

Thanks for the help guys. I will go check tonight after work and get some more info. But after checking the original diagram it seemd odd that the yellow wire that is no longer needed was connected to the Battery terminal on the HEI and hanging loose on the other end. I think this is the problem, no power to the iginion or coil.

Jay after looking at your modified diagram for the HEI swap the orange/purple wire should now connect to the power terminal on the HEI correct?Thanks for the help so far, I will take a look after work.

Forget the orange/purple wire, you will need to run a new wire from the ignition unfused terminal on the fuse block to the bat terminal on the HEI coil.
The HEI distributor needs a full 12 volts to work properly and it must be an ignition keyed on source otherwise it will run down the battery. The O/p wire is a resister wire that drops the voltage to the points coil down to nine volts after the engine is running. If you don't do this you will have a miss that you can't find when you're driving. There is a FAQ for all this written by none other than LHM.

[jayharrell]

hmm... LHM calls it again. I'll have to look into the HEI wire.

[65-72 chevytoys]

LHM you are the man. I got a chance to work today and started the blazer today for the first time in a year. I got the starter to turn with the screwdriver, so I stared chasing the red wire that goes across the core. Sure enough it was burnt and disconnected. I wired it back together and after some priming got the engine to fire and she ran in the garage for several minutes.

Now the bad news. It seems that red wire is melting and why is was disconnected. After several minutes it was disconnected again it burn in two. Any idea what was causing this? Bad voltage regulator? Bad fuse link? Please help!

[Longhorn Man]

fuse link is defenatly gone if the wire is burning up. The fuseable link should pop, protecting the rest of the system. (like a fuse)
You need to search that wire from one end to the other, and find where it is (probably) bumping something else (grounding out).

[65-72 chevytoys]

Longhorn man thanks for the help. When I get a chance to look at it again, how do I tell if that fuse link is bad? Also, if it is bad and it disconnects the circut like a fuse, then when I reconnected that red wire at the battery should that have prevented it from starting in the first place? Thanks for your advice and helping me get it started and to run for just a little while. Yesterday was the first time it started in a year.

[65-72 chevytoys]

I had some time last night and went to check the voltage on the red wire like everyone has recommended. I have 12.4V along that red wire all the way from the battery across the fuse link to the VR and Alt. and back to the firewall side of the fuse block. I also checked the ing. unfused terminal on the inside of the fuse block and nothing.

If I have 12V all the way back to the fuse block, what could would cause that wire to burn itself up with the engine running, and why between the battery and fuse link???

[Longhorn Man]

hmmm, good question.
As for not getting anything on the fues box after knowing it is on the back side, I wpould iunbolt the harness on the back side of the box (On the firewall under the hood) and clean the connections (battery disconnected) And hook it back iup and see what you get.