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73 Hard to start hot

bmack

Member
Joined
Dec 14, 2005
Messages
21
Location
windsor
Corvette
73 blue coupe
When the car has been driven for a bit and it reaches its normal temp, it is hard to start. The engine turns over just fine but it seems that when you let off the key...it starts then???? not when you have the key in the start position. I have been told that it was a bad condensor at the points. I have since changed it over to a HEI ignition and put a new starter, plugs and wires and still have this starting problem. Thank you for your Help.
 

Vettehead Mikey

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Joined
Aug 26, 2003
Messages
3,487
Location
Not that far from Ottawa
Corvette
1973 Coupe
There's two independant wires that feed the distributor, one that provides 12 volts when the key is turned to the 'start' position, and another that provides reduced voltage when the key is in the 'run' position.

Sounds like your 12 volt wire needs some attention.
 

6880 Mike

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Jun 30, 2006
Messages
2,723
Location
The Bluegrass State
Corvette
1968 convertible; 1980 L-82
Heat soak. The starter solonoid picks up heat from the exhaust manifold. Make sure the stock shielding is in place. This helps a little, but often doesn't cure the problem. I read an article which said you could change the spring in the solonoid to a stronger one and stop the problem.
 

Vettehead Mikey

Well-known member
Joined
Aug 26, 2003
Messages
3,487
Location
Not that far from Ottawa
Corvette
1973 Coupe
6880 Mike said:
Heat soak. The starter solonoid picks up heat from the exhaust manifold. Make sure the stock shielding is in place. This helps a little, but often doesn't cure the problem. I read an article which said you could change the spring in the solonoid to a stronger one and stop the problem.

He stated that the car turns over just fine.
 

motorman

Well-known member
Joined
Mar 7, 2002
Messages
849
Location
pa
Corvette
2008 Crystal Red Tint Coat
bmack said:
When the car has been driven for a bit and it reaches its normal temp, it is hard to start. The engine turns over just fine but it seems that when you let off the key...it starts then???? not when you have the key in the start position. I have been told that it was a bad condensor at the points. I have since changed it over to a HEI ignition and put a new starter, plugs and wires and still have this starting problem. Thank you for your Help.
sounds like a bad ignition switch
 

bmack

Member
Joined
Dec 14, 2005
Messages
21
Location
windsor
Corvette
73 blue coupe
Vettehead Mikey said:
There's two independant wires that feed the distributor, one that provides 12 volts when the key is turned to the 'start' position, and another that provides reduced voltage when the key is in the 'run' position.

Sounds like your 12 volt wire needs some attention.
Dear Mikey, does the 12 volt wire you speak of go to the positive side of the coil??? And could it be a bad coil? I have changed everything else. Thank you for your help. Barry
 

Jack

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Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
bmack said:
Dear Mikey, does the 12 volt wire you speak of go to the positive side of the coil??? And could it be a bad coil? I have changed everything else. Thank you for your help. Barry
I'm not mikey ... but YES that wire goes to coil +. And your coil is probably OK.

Your 73 had points when OE ... and the "run" wire that ran to coil + is a resistor wire that reduced the voltage ... the other "start" wire was full 12v to coil+ but it's only hot while starter motor is cranking ... the OE points ignition system operates on a reduced voltage (via resistor wire) once key is released from start to run. When you retrofitted to HEI, it REQUIRES a full 12v when BOTH cranking & running ... the reduced voltage from the old resistor wire is not enough ... and the full 12 from start wire is just that ... hot only when starting/cranking. If there ain't full 12 at HEI when running ... it'll run ... but it won't run right ... and it'll be harder to crank ... even harder when hot. Do a simple voltage check at HEI dist cap's "BAT" terminal while motor is running at high idle & fully charged battery ... if it ain't at least 11.5 vdc ... you need to rewire.
 

bmack

Member
Joined
Dec 14, 2005
Messages
21
Location
windsor
Corvette
73 blue coupe
Jack said:
I'm not mikey ... but YES that wire goes to coil +. And your coil is probably OK.

Your 73 had points when OE ... and the "run" wire that ran to coil + is a resistor wire that reduced the voltage ... the other "start" wire was full 12v to coil+ but it's only hot while starter motor is cranking ... the OE points ignition system operates on a reduced voltage (via resistor wire) once key is released from start to run. When you retrofitted to HEI, it REQUIRES a full 12v when BOTH cranking & running ... the reduced voltage from the old resistor wire is not enough ... and the full 12 from start wire is just that ... hot only when starting/cranking. If there ain't full 12 at HEI when running ... it'll run ... but it won't run right ... and it'll be harder to crank ... even harder when hot. Do a simple voltage check at HEI dist cap's "BAT" terminal while motor is running at high idle & fully charged battery ... if it ain't at least 11.5 vdc ... you need to rewire.
Thank you Jack (nice looking car by the way) The problem that I am having with the HEI is the same as with the points. It starts fine cold and seems to run fine but when its hot, it still cranks over nice but just when you let off the key it wants to catch and start. Jack, how would I have to rewire to get a full 12 at the pos. side of the coil?? Thanks, Barry
 

Jack

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Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
bmack said:
Thank you Jack (nice looking car by the way) The problem that I am having with the HEI is the same as with the points. It starts fine cold and seems to run fine but when its hot, it still cranks over nice but just when you let off the key it wants to catch and start. Jack, how would I have to rewire to get a full 12 at the pos. side of the coil?? Thanks, Barry
First, check voltage at HEI dist cap's "BAT" terminal just as suggested above. If you're down on power there ... follow that resistor wire back to harness' bulkhead connector at firewall ... you can extract that resistor wire out of bulkhead connector and replace with a stranded 10g or 12g wire.

*Warning* When probing the BAT terminal at cap ... be careful ... DO NOT permit a short between cap's BAT and TACH terminals. With motor running at high idle ... With voltmeter, measure voltage between BAT terminal and any good chassis or motor ground.
 

bmack

Member
Joined
Dec 14, 2005
Messages
21
Location
windsor
Corvette
73 blue coupe
Jack said:
First, check voltage at HEI dist cap's "BAT" terminal just as suggested above. If you're down on power there ... follow that resistor wire back to harness' bulkhead connector at firewall ... you can extract that resistor wire out of bulkhead connector and replace with a stranded 10g or 12g wire.

*Warning* When probing the BAT terminal at cap ... be careful ... DO NOT permit a short between cap's BAT and TACH terminals. With motor running at high idle ... With voltmeter, measure voltage between BAT terminal and any good chassis or motor ground.
Thanks again Jack! I will go out and get a voltmeter and check it. I'm working afternoons so I don't have a lot of time today but I was just out in the garage and checking to see if all the connections were good (plug wires coil wires etc.) I was playing around with the carb (mixtures) and found that 4 bolts on the carb were a little loose (not much though) I snugged them up and I could tell a little difference. Barry
 

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