Starting trouble V8 swap (1 Viewer)

[jp_waltz]

1964 40 w a V-8 swap
This is for the folks that are familiar with 350 swaps. Quick background…I bought this 40 from a guy who didn’t know much about it and didn’t have any details to share that might help.
To the best I can find, it’s a 1995 or so Chevy TBI 5.7 that has run great for the last two years but now it won’t start. A few days ago I went to start it and it sounded like the starter stayed engaged. Some smoke came out from underneath the dash. (See pictures posted). It won’t start at all now. I’ve replaced the five prong ignition relay, but there’s this odd in line “fuse” that I’ve never seen. It appears to have been where the smoke was coming from and there’s a melted spot in the middle of it that the picture will show. Does anybody know if this is an in-line fuse or some kind of protection device? There’s a wire that plugs into a block that’s attached to my steering column, and another wire that goes into the rats nest that I was gifted with from the previous owners. The other side appears to go to the relay I replaced. It cranks, but I’m not getting fire anymore, may be due to the melted plastic block?
Thanks in advance
Paul

 

[B y r o n]

You're going to have to provide more than the information or pictures you have posted to resolve this issue. Like what the red and black wires attach to also possible wiring for ecu and ignition.

 

[jp_waltz]

You're going to have to provide more than the information or pictures you have posted to resolve this issue. Like what the red and black wires attach to also possible wiring for ecu and ignition.

The wire on the bottom of the picture circled in blue goes to a 5 prong relay that I’m assuming is for the ignition because the top black wire circled in green goes to a “junction” attached to the column behind the dash. The junction also has a group of wires coming out of it that go way up into oblivion and for the life of me I can’t figure out where they go. My best guess is ignition related due to it being on the column. There’s only one wire in and one wire out of the block in the picture. All of the others were cut prior to installation.

 

[peesalot]

If none of the others were attached to anything I would delete that part, twist em up and see what happens, splice properly if works.

 

[jcj_78FJ40]

You say the white wire goes to a relay? Is the relay connected to the starter solenoid?

 

[jp_waltz]

You say the white wire goes to a relay? Is the relay connected to the starter solenoid?

Yea the white wire goes into a relay but I’m not sure where the relay goes to. It’s bundled in the main loom and disappears but may go to the solenoid. I ran out of time to look any further and the wiring is a mess under there. If I can find out what the black square is that is attached into the ignition, I may be able to track it down better.

 

[jp_waltz]

this is where the smoke was coming from. It melted the plastic so I’m thinking that it’s not doing what it’s supposed to be doing anymore. I’m wondering if I had a bad ignition relay that kept my starter engaged and left the circuit open overheating that black piece next to my ignition

 

[jcj_78FJ40]

Going by the symbols and the way it's hooked up, it's a diode that only allows current from the switch to the white wire (current would be blocked from going back to the switch). Hard to say why a diode is needed in the ignition circuit. To your point, definitely replace it if it's burnt.

 

[jp_waltz]

Going by the symbols and the way it's hooked up, it's a diode that only allows current from the switch to the white wire (current would be blocked from going back to the switch). Hard to say why a diode is needed in the ignition circuit. To your point, definitely replace it if it's burnt.t

Thanks…any thoughts on what to replace it with? An in line fuse? I can’t seem to find that part anywhere.

 

[jcj_78FJ40]

Apparently, back feeding from the alternator to the ignition switch is a thing. See info from following link

You could try this.

Painless Wiring

Painless Performance Alternator Backfeed Diode Kit, Part Number 30720.

www.painlessperformance.com

You really need more info on the circuit. Regardless, the diode is not going to hurt anything as long as it's installed correctly.

 

[bhsdriller]

It cranks, but I’m not getting fire anymore, may be due to the melted plastic block?

Are you getting spark/fuel?

 

[76 PTO]

control module is common instant no start with tbi engines.

 

[peesalot]

Just remove that dam thing, its 1 in, 1 out, whatever else it powered when triggered is mute point now. Just twist those together and start it, you thinking way to much. To satisfy yourself, take that melted thing out and break it open, you'll know exactly what it DID.

 

[bikersmurf]

Looks like something like this...
Amazon product ASIN B007HRO564

 

[jp_waltz]

Apparently, back feeding from the alternator to the ignition switch is a thing. See info from following link

You could try this.

Painless Wiring

Painless Performance Alternator Backfeed Diode Kit, Part Number 30720.

www.painlessperformance.com

You really need more info on the circuit. Regardless, the diode is not going to hurt anything as long as it's installed correctly.

Great info. I’m thinking that might be what was happening. I talked to an electrical engineer friend of mine last night and he gave me some good stuff to think about

 

[jp_waltz]

It cranks, but I’m not getting fire anymore, may be due to the melted plastic block?

Are you getting spark/fuel?

I ran out of time to look yesterday but once I get a new diode installed I’ll chase down spark and fuel.

 

[jp_waltz]

Looks like something like this...
Amazon product ASIN B007HRO564

Ya that appears to have the same function.