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-   -   HEI Wiring Problems... stumped... (http://www.hotrodders.com/forum/hei-wiring-problems-stumped-221083.html)

loudandproud 06-27-2012 07:30 PM

HEI Wiring Problems... stumped...
 
Here is the deal.

Just got done with putting a carburated sbc in my C1500 chevy pickup. Thing runs great.

For mockup I ran the HEI distributor right off the battery. Got the motor timed for 32* total advance, all in at 3200 rpm. Initial is about 10*.
All was good.

After getting everything buttoned up, it was time to go back and tie up the loose ends.

I decided to hook the HEI up to a keyed- hot wire.

After doing this, the motor would start and run fine, but after I turned the key off, the dash lights would stay on, and the motor would keep running. To shut the motor off I would have to go out and unplug the Keyed hot wire from the BAT terminal on the HEI. As soon as I did this, the motor would shut off and the dash lights would turn off.

Hmmm. Interesting. Checked the keyed hot again... sure enough... when unplugged from the dizzy it acts as expected. Key on: 14.1v+ , Key off: 0volts.

I figured the HEI was back feeding somehow into the wiring, so then i decided to hook it up to a relay.

The coil was then hooked up to a DIFFERENT keyed hot (radio terminal in the fuse block). I then hooked up the common to the battery and the N.O terminal to the BAT terminal on the battery.

Check everything with a voltage tester... all good. Key on: 14.1v+ Key off: 0 volts

Try to start the motor...

This time it cranks and cranks and cranks and then starts chugging. BUT NOT THE GOOD KIND! Fuel starts spraying out of the carberator and the motor is carrying on. Shut the key off and it dies. Acts like the timing is WAY off. The motor was actually bumping of the starter and trying to fire over backwards. Wierd.

Try again... Does the same thing.

Try again... Does the same thing.


I think ... hmmm. I wonder if the cam or dizzy jumped timing.

So I hot wire it back up to the battery. Crank it over... **** you not the first revolution the motor fires right up and runs perfect.

Switched it back to the relay thinking it was a fluke.. nope.

WTF is going on?

Im beyond confused.

bigblockragtop 06-27-2012 07:44 PM

Not a wiring guru but somehow when you hook it up to ignition power it(I think maybe) is sending power through the ground which is why it is lighting up the dash. How is the motor grounded and is the chasis grounded? Just a guess hope it helps

T-bucket23 06-27-2012 09:36 PM

it sounds like alternator back feed. You may need to put a diode in the feed line to the alternator. this is usually due to some other wiring issue. if you do a search here for diode you should find some info.

CQNRQY 06-29-2012 10:17 AM

Theres got to be a wrong electrical hook up.
Try unplugging the two wire plug at the alternator.
Then start your engine see if you can shut it off.
If so your alternater is back feeding through the idiot light(brown wire)
If that doesnt work.. it try unhooking the bat wire at the alternator then start it and shut it down if that works its back feeding that way.
Hope this helps :thumbup:

Quote:

Originally Posted by loudandproud (Post 1569182)
Here is the deal.

Just got done with putting a carburated sbc in my C1500 chevy pickup. Thing runs great.

For mockup I ran the HEI distributor right off the battery. Got the motor timed for 32* total advance, all in at 3200 rpm. Initial is about 10*.
All was good.

After getting everything buttoned up, it was time to go back and tie up the loose ends.

I decided to hook the HEI up to a keyed- hot wire.

After doing this, the motor would start and run fine, but after I turned the key off, the dash lights would stay on, and the motor would keep running. To shut the motor off I would have to go out and unplug the Keyed hot wire from the BAT terminal on the HEI. As soon as I did this, the motor would shut off and the dash lights would turn off.

Hmmm. Interesting. Checked the keyed hot again... sure enough... when unplugged from the dizzy it acts as expected. Key on: 14.1v+ , Key off: 0volts.

I figured the HEI was back feeding somehow into the wiring, so then i decided to hook it up to a relay.

The coil was then hooked up to a DIFFERENT keyed hot (radio terminal in the fuse block). I then hooked up the common to the battery and the N.O terminal to the BAT terminal on the battery.

Check everything with a voltage tester... all good. Key on: 14.1v+ Key off: 0 volts

Try to start the motor...

This time it cranks and cranks and cranks and then starts chugging. BUT NOT THE GOOD KIND! Fuel starts spraying out of the carberator and the motor is carrying on. Shut the key off and it dies. Acts like the timing is WAY off. The motor was actually bumping of the starter and trying to fire over backwards. Wierd.

Try again... Does the same thing.

Try again... Does the same thing.


I think ... hmmm. I wonder if the cam or dizzy jumped timing.

So I hot wire it back up to the battery. Crank it over... **** you not the first revolution the motor fires right up and runs perfect.

Switched it back to the relay thinking it was a fluke.. nope.

WTF is going on?

Im beyond confused.


48panel 06-29-2012 09:18 PM

Your problem is definitly alernator backfeed. but the radiocircuit is not powered during crankingwhich is why your engin did not start with the relay. putting the relay back in line to the dist. through a circuit that is hot in crankand run should correct that problem and take care of the back feeding from the alt.Hook the hot at the dist. to the hot on th coil of the relayand take the other side to ground. then hook a separate line ,from a line that is hot at all times though a fuse ,to the line into the contacts of the relayand the N.O. side to the dist.


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