Engine will not turn over when warm.
Thread Starter
Navigator
Joined: Jun 2009
Posts: 9
Likes: 0
Engine will not turn over when warm.
My 1973 Corvette Big Block will not roll-over when the engine is warm. I've replaced the starter and still have the same problem. When cold, the engine rolls and starts just fine. When placing a jumper wire from the starter to battery (key on)the vehicle will start right up. But when trying to start the vehicle using the key, the starter will not engage or roll. Again this problem only occures when the engine is warm. By allowing the engine to cool for a couple of hours the vehicle will start right up using the key. Any ideas on what might be the cause?
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
are you running headers? heat soak
are the bat cables good or running close to heat source? heat soak
did the new starter come with a new engage solenoid?
What is the CCAmps of the battery? wrong bat
are the bat cables good or running close to heat source? heat soak
did the new starter come with a new engage solenoid?
What is the CCAmps of the battery? wrong bat
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
Starter heat soak. There are heat shields you can buy to stop this. There should be a small one one the starter already. Is it there? Here's a link to Summit that shows a sample of shields.
http://www.summitracing.com/search/?...20shield&dds=1
Gary
http://www.summitracing.com/search/?...20shield&dds=1
Gary
CF Community Team
Joined: Oct 2004
Posts: 19,357
Likes: 5,242
From: Cape Cod, Mass.
2025 C6 of the Year Finalist - Unmodified
2025 C8 Z06/7/E-Ray of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
2021 C8 of the Year Finalist Unmodified
2020 Corvette of the Year Finalist (performance mods)
2019 C1 of Year Winner (performance mods)
2017 Corvette of the Year Finalist
2016 C2 of Year
2015 C3 of Year Finalist
Check all of your battery connections thoroughly.
Safety Car
Joined: Sep 2007
Posts: 4,458
Likes: 330
From: Indy Indiana
is your battery old? it takes alot of amps to crank a hot big block .. go out and get you the biggest, most cold cranking amp battery you can find... even a 3 year old battery usually has lost half its cranking rating when new...
I had the same problem several times with big blocks or big pontiacs.. a 1000 amp battery cured it every time...
I had the same problem several times with big blocks or big pontiacs.. a 1000 amp battery cured it every time...
Team Owner
Joined: Jul 2008
Posts: 23,419
Likes: 22
From: In limbo
St. Jude Donor '13-'15, '17 thru '22
Let me make sure I understand your post properly: Starting the engine cold works fine. Starting the engine warm with the key doesn't work, but if you leave the key in the "on" position and jump from the battery to the starter motor, it starts right up. Correct?
If so, you can eliminate your battery and your starter motor as the problem, which means you have a poor connection somewhere in the system.
I had a similar problem when I brought my car home last year, started great when cold, but when hot, the starter would barely turn the engine over. Mine turned out to be some boogered up connections on my solenoid. I replaced the solenoid and (knock wood) I haven't had any trouble starting the car since.
Heat soak can play a role, and there is nothing wrong with putting a heat shield on your starter motor (I have one), but in this case, I doubt it will solve your problem since jumping the amperage to the starter works when the starter is hot.
If so, you can eliminate your battery and your starter motor as the problem, which means you have a poor connection somewhere in the system.
I had a similar problem when I brought my car home last year, started great when cold, but when hot, the starter would barely turn the engine over. Mine turned out to be some boogered up connections on my solenoid. I replaced the solenoid and (knock wood) I haven't had any trouble starting the car since.
Heat soak can play a role, and there is nothing wrong with putting a heat shield on your starter motor (I have one), but in this case, I doubt it will solve your problem since jumping the amperage to the starter works when the starter is hot.
Instructor
Joined: May 2006
Posts: 223
Likes: 1
From: Kennesaw GA
My 1973 Corvette Big Block will not roll-over when the engine is warm. I've replaced the starter and still have the same problem. When cold, the engine rolls and starts just fine. When placing a jumper wire from the starter to battery (key on)the vehicle will start right up. But when trying to start the vehicle using the key, the starter will not engage or roll. Again this problem only occures when the engine is warm. By allowing the engine to cool for a couple of hours the vehicle will start right up using the key. Any ideas on what might be the cause?
My point is that if you're having high resistance in the starting circuit using the key, you should have the same amount of resistance using a jumper/screwdriver/remote starter button.
The solenoid circuit just energizes the path between the battery and the starter, so there's no huge amount of power in the soleniod/starting circuit.
Usually fixing a 'hot start' problem, is as simple as replacing 30+ year old cables and terminals and ensuring you have a good battery. This fixed it on my '69 427.
By the way I'm not a big believer in 'heat soak'.
Shawn
Last edited by GruntyPants; Jul 23, 2009 at 02:40 PM. Reason: To try to look smarter.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Instructor
Joined: May 2006
Posts: 223
Likes: 1
From: Kennesaw GA
Now that I re-read the OP, it says that the starter won't engage, meaning the solenoid is faulty. You can replace it with a stock one, and might have this issue again in a few years, or run a remote solenoid on the firewall.
Racer
Joined: May 2007
Posts: 370
Likes: 0
From: Cherry Hill N.J.
could possibly be battery ground to frame located under battery box .
Access is from under car.....A lot of dirt, rust,etc, builds up at ground connection.
Remove 1 bolt holding cable to frame,, clean both frame and cable end where bolt attaches and see if your problem is solved......
Good Luck
Access is from under car.....A lot of dirt, rust,etc, builds up at ground connection.
Remove 1 bolt holding cable to frame,, clean both frame and cable end where bolt attaches and see if your problem is solved......
Good Luck
Instructor
Joined: Jan 2005
Posts: 146
Likes: 1
From: Roanoke Rapids NC
I'm having the same problem but with a '74 and 350 engine, but mine only does it if I've had the headlights burning and the motor is hot. If I cut the car off before I kill the lights it will not start (I don't just leave the lights on either.) Everything Else in the car works great and seems like the battery has plenty of juice but not enough to even make the starter engage. Also, jumping the vette with another car fixes it instantaneously. The only things I can think of are "heat sink" in the starter, or that the starter isn't grounding well when the engine is hot. Any other suggestions would be highly appreciated, I think I will try the starter insulator wrap.
Thanks,
Brad
Thanks,
Brad
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
I'm having the same problem but with a '74 and 350 engine, but mine only does it if I've had the headlights burning and the motor is hot. If I cut the car off before I kill the lights it will not start (I don't just leave the lights on either.) Everything Else in the car works great and seems like the battery has plenty of juice but not enough to even make the starter engage. Also, jumping the vette with another car fixes it instantaneously. The only things I can think of are "heat sink" in the starter, or that the starter isn't grounding well when the engine is hot. Any other suggestions would be highly appreciated, I think I will try the starter insulator wrap.
Thanks,
Brad
Thanks,
Brad
Gary
Racer
Joined: Apr 2006
Posts: 340
Likes: 0
From: Warrensburg MO
Shoot some wires. See if you are getting power to the starter when you hit the ignition switch. If you have power, then it must be starter/solenoid problem. If you don't have power, then you have to trace the wire. Maybe fusible link? I am not sure if they reset or not.
TommyJ
TommyJ
Burning Brakes
Joined: Dec 2007
Posts: 952
Likes: 0
My 1973 Corvette Big Block will not roll-over when the engine is warm. I've replaced the starter and still have the same problem. When cold, the engine rolls and starts just fine. When placing a jumper wire from the starter to battery (key on)the vehicle will start right up. But when trying to start the vehicle using the key, the starter will not engage or roll. Again this problem only occures when the engine is warm. By allowing the engine to cool for a couple of hours the vehicle will start right up using the key. Any ideas on what might be the cause?
Instructor
Joined: Jan 2005
Posts: 146
Likes: 1
From: Roanoke Rapids NC
I can fully see how the solenoid can be getting "heat soak" as I've replaced the starter several times and temporarily solved the issue. But doesn't anyone make a higher quality starter that will stand up to the heat? I've just been using reman. Advance Auto jobs, but I don't know where else to go...
Navigator
Joined: Oct 2006
Posts: 9
Likes: 1
From: Peoria AZ
GM did have a service bulletin way back when... I solved this problem on my '77 and friends 'Vettes by purchasing a special solenoid return spring and special nut from GM. Surprisingly it only took those two parts. Sorry, I don't recall the part numbers as this was done in the early '80s. Perhaps an oldtimer from GM can help. There were articles in Corvette magazines circa 1980.
I solved the same problem in the mid '90s on a truck by simply using a high-speed heater fan relay. One post goes to the battery, one to the start wire (instead of it going to the starter) and the 3rd pin to the relay (in place of the start wire). It never missed a beat.
Also, I never replace a starter. I take mine to a place that rebuilds starters (usually an oldtimers place) and ask them to rebuild it to high performance specs which a good shop can do. I first did this back in the late '60s on my '60 and it would spin anything. When my friends face car wouldn't start with a regular starter we put mine on his car and it cranked like low compression engine!
I don't know if these suggestions will help C4 and later owners but it worked on C3 and earlier vehilcles.
Buz
I solved the same problem in the mid '90s on a truck by simply using a high-speed heater fan relay. One post goes to the battery, one to the start wire (instead of it going to the starter) and the 3rd pin to the relay (in place of the start wire). It never missed a beat.
Also, I never replace a starter. I take mine to a place that rebuilds starters (usually an oldtimers place) and ask them to rebuild it to high performance specs which a good shop can do. I first did this back in the late '60s on my '60 and it would spin anything. When my friends face car wouldn't start with a regular starter we put mine on his car and it cranked like low compression engine!
I don't know if these suggestions will help C4 and later owners but it worked on C3 and earlier vehilcles.
Buz