no spark HEI
Thread Starter
Safety Car
Joined: Jan 2009
Posts: 3,873
Likes: 25
no spark HEI
HI......ramair here. I'll make this short. 81/350, and hei dist. Beleave it or not, key switch in start position......no spark. run position......no spark. off position.......you get a short snap on the spark tester. Hey.......this car ran really good before. previous owner replaced plugs,wires, cap' rotor, I replaced ign mod, coil on dist cap. and lastly the ign switch down on the sterring colum. No results. 12.7v@hot lead at dist. 8.9 during cranking. this is making me cranky. Thanks jim for the steering colum advice. I was thinking the switch was internal. I should have came here first
Drifting
Joined: Jul 2002
Posts: 1,944
Likes: 20
From: The only Corvettes in Highett Victoria
8.9 volts???????????
Bryan,
HEI's are designed to run on 12 volts ALL the time, even when cranking. If you had a pre-'75, I'd say that your ballast resistor was still in the circuit, but an '81 shouldn't have one of those. Even so, I think an HEI should throw a spark at 8.9 volts. Sounds like you need an auto electrician, or a wiring diagram and a circuit tester. Good luck!
Regards from Down Under
aussiejohn
5 months to go
HEI's are designed to run on 12 volts ALL the time, even when cranking. If you had a pre-'75, I'd say that your ballast resistor was still in the circuit, but an '81 shouldn't have one of those. Even so, I think an HEI should throw a spark at 8.9 volts. Sounds like you need an auto electrician, or a wiring diagram and a circuit tester. Good luck!
Regards from Down Under
aussiejohn
5 months to go
Drifting
Joined: Jul 1999
Posts: 1,542
Likes: 43
From: Plano TX
The HEI does need battery voltage as mentioned above during both run mode and start mode. Start mode will be less because the starter is drawing a lot of current and batt voltage will drop. Do make sure the ballast resistor has been removed and there is a direct connection to battery power.
In an older retrofit I use a relay that is close by the ignition swtich lead. I then run a 10 ga wire from the battery lead on the starter to one side of the relay and the other side of the relay I run a 10 ga lead to the HEI Batt terminal.
I looked through your list of parts replaced and notice the pickup coil doesn't appear to be mentioned. This is the coil that tells the ignition module to fire. It sits under the mechanical advance mechanism (you'll see the wires coming out of it). If open circuit you need to pull the dist, drive out the cam gear pin, remove the gear and shim, pull the distributor shaft out from the top (mark where the rotor is pointing before you pull dist). This might take a bit of time working the dist shaft back and forth if it's built up some varnish. Once out replace the pickup coil. You align the coil with the 3 screws making sure the the coil has same clearance all the way around and reassemble dist. Sounds hard to do but it's not. Had one of these fail years ago but took sometime to figure out as the pickup coil is sometimes forgotten about.
In an older retrofit I use a relay that is close by the ignition swtich lead. I then run a 10 ga wire from the battery lead on the starter to one side of the relay and the other side of the relay I run a 10 ga lead to the HEI Batt terminal.
I looked through your list of parts replaced and notice the pickup coil doesn't appear to be mentioned. This is the coil that tells the ignition module to fire. It sits under the mechanical advance mechanism (you'll see the wires coming out of it). If open circuit you need to pull the dist, drive out the cam gear pin, remove the gear and shim, pull the distributor shaft out from the top (mark where the rotor is pointing before you pull dist). This might take a bit of time working the dist shaft back and forth if it's built up some varnish. Once out replace the pickup coil. You align the coil with the 3 screws making sure the the coil has same clearance all the way around and reassemble dist. Sounds hard to do but it's not. Had one of these fail years ago but took sometime to figure out as the pickup coil is sometimes forgotten about.
Thread Starter
Safety Car
Joined: Jan 2009
Posts: 3,873
Likes: 25
Dave.......you were right!
The HEI does need battery voltage as mentioned above during both run mode and start mode. Start mode will be less because the starter is drawing a lot of current and batt voltage will drop. Do make sure the ballast resistor has been removed and there is a direct connection to battery power.
In an older retrofit I use a relay that is close by the ignition swtich lead. I then run a 10 ga wire from the battery lead on the starter to one side of the relay and the other side of the relay I run a 10 ga lead to the HEI Batt terminal.
I looked through your list of parts replaced and notice the pickup coil doesn't appear to be mentioned. This is the coil that tells the ignition module to fire. It sits under the mechanical advance mechanism (you'll see the wires coming out of it). If open circuit you need to pull the dist, drive out the cam gear pin, remove the gear and shim, pull the distributor shaft out from the top (mark where the rotor is pointing before you pull dist). This might take a bit of time working the dist shaft back and forth if it's built up some varnish. Once out replace the pickup coil. You align the coil with the 3 screws making sure the the coil has same clearance all the way around and reassemble dist. Sounds hard to do but it's not. Had one of these fail years ago but took sometime to figure out as the pickup coil is sometimes forgotten about.
In an older retrofit I use a relay that is close by the ignition swtich lead. I then run a 10 ga wire from the battery lead on the starter to one side of the relay and the other side of the relay I run a 10 ga lead to the HEI Batt terminal.
I looked through your list of parts replaced and notice the pickup coil doesn't appear to be mentioned. This is the coil that tells the ignition module to fire. It sits under the mechanical advance mechanism (you'll see the wires coming out of it). If open circuit you need to pull the dist, drive out the cam gear pin, remove the gear and shim, pull the distributor shaft out from the top (mark where the rotor is pointing before you pull dist). This might take a bit of time working the dist shaft back and forth if it's built up some varnish. Once out replace the pickup coil. You align the coil with the 3 screws making sure the the coil has same clearance all the way around and reassemble dist. Sounds hard to do but it's not. Had one of these fail years ago but took sometime to figure out as the pickup coil is sometimes forgotten about.
Tech Contributor
Joined: Jun 2004
Posts: 20,910
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Just a minor correction to some comments that were made above.
The HEI does not "need" 12 volts. It is designed to run just fine from 6 to 16 volts. (Anyone who has tried to start their car in the frozen north, where I'm originally from, will appreciate that the ignition system will still fire the plugs when the starter drags the system voltage down low when turning against cold thick oil). Also, the internal adaptive dwell keeps things from frying in the event of a voltage regulator failure that causes the alternator voltage to go out of spec in the high direction. This adaptive dwell feature is also the reason that the HEI does not need a ballast resistor to limit the peak dwell current.
My kudos to Dave for suggesting an inspection of the pickup coil. The signal wires are subjected to flex every time the vacuum advance arm and plate moves. This will eventually cause a fatigue break in the signal wires.
While 8.9 volts should be just fine for the ignition system to operate during cranking, a doublecheck of your electrical connections, as suggested above, is always a good idea.
The HEI does not "need" 12 volts. It is designed to run just fine from 6 to 16 volts. (Anyone who has tried to start their car in the frozen north, where I'm originally from, will appreciate that the ignition system will still fire the plugs when the starter drags the system voltage down low when turning against cold thick oil). Also, the internal adaptive dwell keeps things from frying in the event of a voltage regulator failure that causes the alternator voltage to go out of spec in the high direction. This adaptive dwell feature is also the reason that the HEI does not need a ballast resistor to limit the peak dwell current.
My kudos to Dave for suggesting an inspection of the pickup coil. The signal wires are subjected to flex every time the vacuum advance arm and plate moves. This will eventually cause a fatigue break in the signal wires.
While 8.9 volts should be just fine for the ignition system to operate during cranking, a doublecheck of your electrical connections, as suggested above, is always a good idea.
Thread Starter
Safety Car
Joined: Jan 2009
Posts: 3,873
Likes: 25
HEI....... bad news guys.
Dudes.............I replaced the pickup coil as well, and no results. I can not believe it. I replaced every thing elec in and on the dist. How about a computer problem? It manages the advance right? I bet it's messing with regular operation. I'm thinking I'll stick in a regular HEI non computer controled, and see if it fires up. My buds got one. More later. Stay tuned..........bryan.
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Thread Starter
Safety Car
Joined: Jan 2009
Posts: 3,873
Likes: 25
HEI.......more....
Thanks for asking. No not yet. But I unplugged the 4 pin connector from the dist to the harness....go's to the computer and anti-theft I bet. And it fired right up as normal. I wonder if the anti-theft is the problem? can it be bypassed ? I've got to go take an head pill. Back later............bryan.