My 1974 Corvette has a hot start issue I’ve been unable to resolve. It starts without fail when cold and I can push start it when hot. All other electrical comes on but when I turn the key after the engine warms up the starter won’t engage. I’ve pulled the starter and had it tested. No issues. I pulled the solenoid, cleaned the leads and replaced it with a new one. I pulled the starter ground and battery ground to the frame and cleaned them up. I’ve replaced the battery and I placed a heat shield around the starter. I checked wiring as best I could and tied it away from hot areas as best I could. It still doesn’t restart hot. Does anyone have suggestions on where I go next?

 

Have you checked or replaced the positive cable from the battery to the starter?

 

YEs I agree!! check the ground and positive leads at the battery and the ground on the frame. Makes sure the engine has good grounds. When the engine and starter are hot they take more amps to crank. IF its not turning over at all which I would guess from the push start comment then I would check that and maybe have your battery load tested, it may be weak


as peterbuilt said check the cables as well, if they are swollen any where along their length its corrosion, replace them

 

The ends were good and I had no trouble cold so I didn’t replace it. I’ll inspect it and move to the power steering project since I don’t have the right ends on hand and cable that long to make a new one now. I can order what I need and come back to the startup gremlin in a few weeks.

 

Look into testing for "voltage drop". You can have continuity and current flow, but if the wire is compromised, there's not enough voltage to activate the starter.

There are good YT videos explaining and showing how to test for it.

 

Possible issue is the brushes. Under heat the motor requires more current, and if the brushes are worn and their springs are weak from heat, the starter just won't turn. Problem with bench testing is the starter is cold.

 

I had this problem on a 67 Mustang some 20+ years ago. The problem was I had too much initial timing in the distributor. I backed it off about 3 deg and that fixed it. Try it and if that doesnt work you can quickly put it back. Also check the engine ground. I have seen that same hot start problem when the engine doesnt have a good ground to the frame.

 

I solved the same problem on our '72 a long time ago by cutting off the last 1" or so of the leads going to the starter, and installing new terminal ends. I'd noticed that a number of individual strands of copper had broken over the years, so I re-terminated in 'fresh', unbroken copper.

 

I had that issue years ago with my 69. Fired up great, got to a car show, sat for an hour and then nothing. Turn the key, nothing. I was about to call a flatbed after a couple of hours, but it fired up and got me home.
I checked the starter, rebuilt the solenoid with a kit that was once available from GM with a stiffer spring, and wrapped it for protection against heat soak. Finally, I checked the wire leads and spliced in fresh copper wire by soldering and soldered on new terminal ends. That resolved it for me.

 

Starter relay? Starter interrupt switch from clutch pedal?

 

Had the same problem on my 77 and tired 20 different things and turned out that the starter was getting heat stroke.

Replaced the starter and problem gone

 

Welcome to the Corvette Forum Goose1!

The best solution in my opinion would be to swap the original starter out for one of the newer smaller, permanent magnet, gear drive starters. I used on on my BB with high compression and it spins the engine fast enough to start it every time no matter what the heat level is.

Another way to resolve the issue is to use the Timing Pull back feature of the newer MSD boxes. The idea is to pull the timing while cranking the engine which unloads the starter motor and allows the engine to crank freely. This system works very well with my gear drive starter and allows my engine to crank fast enough to start it right away. The Holley EFI software also offers this option and I strongly suggest anyone with Hot engine starting issues try it. The timing is returned to full timing at ~800 rpm and the car purrs right along.

The reason we ask people to check their battery cables is because we have seen many battery cables fail over the years. The ground connection should be kept clean at the chassis but for some reason they still get corroded. If the battery wire gets a tiny pin ***** in the outer jacket then water can get into the cable and starts corrosion on the fast track. As the corrosion forms it will make a bulge in the wire where the corrosion is swelling under the jacket. Over time the corrosion will start breaking down the connection and resistance will be introduced into the wire. This does not end well and requires a cable to be replaced.

Testing the battery voltage while cranking is always a good idea, I use a multi-meter with a Min-Max function and with it you can see the minimum voltage the battery dropped to before the charging system takes over and gives you a new maximum number. This allows you to se what the state of the battery is in as well as show you if the engine is charging as needed.

Battery connections should be checked and if needed cleaned every year or so. I like to ensure that my connections are good during my pre-ride inspections of the Corvette. At least once a year you should isolate the battery and charge it by itself up to at least 2.5 volts per cell (15 Volts) to get the battery gassing which will stop the stratification of the electrolyte and make the battery keep it's capacity longer. I use a 15 amp battery charger and have no problems getting the electrolyte mixed up. I isolate the car so that higher voltages don't hurt any of the electronics during the charging process.

 

I have posted this answer so many times I think I'm going to write it up and save it so I can just cut and paste next time.
Assuming you're not interested in originality, get yourself a late(r) model gear reduction starter. I used one from a 1996 full size Chevy truck. Smaller (easier to work on), lighter, and starts the car every time. I installed mine 25 years ago. No problem ever since.

 

I'll just put this out there because I had been fighting this problem for about a year. But mine is a '72 automatic so.... From suggestions on this forum, my solution wound up being replacing the neutral safety/backup switch. Who'd a thunk it but it solved my problem. After looking at the obvious areas of battery, battery wiring, starter and wiring, location of the starter (getting hot), and ignition switch, the last 2 options seemed to be the ignition switch or the safety switch. The replacing the last one was the solution.

 

Starter solenoid after its been heat soaked. I had to leave my car idling.... or turn it off but leave the hood up. I believe they had a heat shield originally.

I installed a modern starter. Car starts up great now. A bit overkill at $250 shipped... but that's my style

https://www.summitracing.com/parts/PWM-9526

 

I'll reply here also for future reference.
Same solution for my 79 auto.
After years of knowing it wouldn't start after being hot I just put up with it. Knew I'd spend at least 1/2 hour at a cruise nite or whatever if I shut it down.
Checked starter and wiring, no help.
One night I tried starting it in neurtral, nothing, then jiggled the shifter while turning the key and it started right up.
Slight adjustment of the switch on the shifter.

 

Had it happen on my 77 years back... blew $800 chasing it down... ground wire was toast inside the shielding
Replaced all my grounds with new thicker wires/ends.....

 

On my 80 I added an additional wire to the S terminal on the solenoid. The wire was long enough to reach the Batt terminal on the alternator. When heat soak occurred I touched the wire to the Batt terminal and it would start. Doing this proved the starter and large cables were good. Connection from ignition switch could not supply enough current. I put a relay in that closed when ignition was in the start position. This closed a connection from the battery terminal on the started to the S terminal on the starter solenoid. Never had another issue but later did put in a gear reduction starter to save weight also.

 

As has been suggested; install a modern, lightweight Permanent Magnet Gear Reduction Starter aka PMGR aka PG260 and install New, Correct Bolts.
The How & Why included in this two-page TSB from industry leader REMY. Includes Part Numbers for both starters and bolts.

https://autoprollc.com/wp-content/up...eb2016_web.pdf

Corrosion creeps and hides beneath cable insulation. A heat wrap can just as easily trap heat within as it shields from exhaust heat; sheetmetal shield usually better.
Most PMGR/PG260 can be had for under $125, even $100. Their smaller profile typically positions them farther away from exhaust.
If a starter has thru-bolts/screws, both perpendicular to & through sides of starter case, it has field coils but Not permanent magnets.

 

If you can't get adequate current to the starter/solenoid, it doesn't matter what starter you install....it still won't start. The front mount/bracket on many C3 starters is the primary connection for electrical ground, via the ground jumper wire from frame to right side engine mount. If that grounding system isn't fully intact, you will have starting problems, even when cold...but definitely when hot. C3 starters have worked flawlessly for decades. The starter CAN be a problems IF the brushes are worn out. Otherwise, GM starters are virtually bullet-proof.
Do yourself a favor and check out the presence and condition of primary current paths (positive AND negative), before you throw $$$ at the problem.
Primary candidates for 'no start' issues are:
1. Neutral start switch (battery GOOD, no 'clicking' when trying to start)
2. Starter SOLENOID (battery GOOD, 'clicking' when trying to start)
3. Weak battery (shows adequate VOLTAGE, but inadequate current capacity)
4. Bad 12vdc supply and/or grounding cables going to the starter (including needed front bracket)
5. Worn out brushes on starter
6. Bad ignition switch
7. Bad wiring on ignition switch