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Engine Runs a Few Seconds After I Turn Off Ignition

BGBronco

Contributor
N A S H V I L L E
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Jun 23, 2017
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1,542
Loc.
Tennessee
76 w/ Painless Harness.

We just did some upgrades (Holley Sniper, Hyperspark Distributor / Ignition, and Blaster Coil). All seems to be working well except when I turn off the ignition there is a delayed response of a few seconds before the engine turns off.

Trying to figure out if my switch is going bad or something specific to my new set up. Thx
 

Quick & Dirty

Sr. Member
Joined
Feb 15, 2004
Messages
826
Do you have an internal regulated alternator, or the original style external regulator? Sometimes the internal regulator types will backfeed the ignition through the exciter wire connection. Adding a diode to the exciter will prevent that.

 
OP
OP
BGBronco

BGBronco

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Hard to read but it looks like its either a 50 or 60A so I'm assuming the original style.
 

DirtDonk

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Bronco Guru
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Nov 3, 2003
Messages
47,275
Without knowing exactly how you connected the Hyperspark and Sniper, we might have to just throw out suggestions while you dig into things physically to see what's going on.
You might try disconnecting a couple of things before you dig too far in though.
Before you turn the key off the next time, pull the two small wires off of the starter relay/solenoid (if you still have the Brown "I" wire?) to isolate anything with a defective relay. Then see if it shuts off directly or still runs on.
What else do you have connected to the small terminals of the relay/solenoid? Anything additional from the Sniper and such, or just the usual two wires (Red w/blue and Brown) of the stock setup?

For the alternator, yes it sounds like a standard 1G series. So you do have a separate voltage regulator mounted to the fender or firewall?
How is it wired? Three wires or four? Which positions are the different wires in?

And just as important for this quest perhaps, got any pics of the under-hood area you can share? Generally around the battery, starter relay and alternator? Then around the Sniper and distributor?

Thanks

Paul
 

walls

Full Member
Joined
Oct 4, 2010
Messages
222
Electric fan will sometimes allow motor to continue running until it stops spinning. Back feeds and may require a diode
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,821
Electric fan will sometimes allow motor to continue running until it stops spinning. Back feeds and may require a diode
I was about to say the same thing. Motors will act as generators with inertia keeping them spinning.

The first time I tried an electric fan I tied it into the ignition. Did the same thing. Thought about it and tried something. Going down the highway I could turn off the ignition and the ram air keeping the fan spinning was enough to keep the ignition active. Never did test how slow I could go before it would stall. I have a friend who has a beater mustang and an electric fan tied into the A/C. When he gets up to speed the fan will keep the compressor energized and it will freeze up the evaporater.

Since the EFI stuff you are dealing with only takes a little bit of power on the activation wire to stay on it would be easy to get that. If not an electric motor coasting down, a capacitor powering down (car audio?).


More thoughts...
Ignition alone may not be turning off with the hyper spark. The sniper having the fuel turned off but the intake still full of air/fuel. You could get a few more cylinder fires off that fuel before the engine starves for fuel. Watch the sniper display as you turn the ignition off. It should turn off right away. That will tell you if the EFI is shutting down with the ignition switch or not
 
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