Hot start problem?

In April of 2007 I purchased my dream car, a 1969 Pontiac Firebird 400 convertible. At that time I had a hard time starting it, lots of cranking waiting for the engine to fire. Sometimes the starter?s pinion gear didn?t mesh with the ring gear on the crankshaft?s flywheel and made a grinding noise. In December 2007 I replaced the starter, I?m unsure whether it was a 1 or 2 post / low or high torque, but it was stock appearing.

I didn?t discover the current problem until driving a long distance for the first time with this new starter. It was in July of this year, very hot, and on the highway off ramp, slowing suddenly I stalled. I believe this was because my idle was set too low. I pulled over and when I tried to restart there was total silence. The headlights and other electrical components worked and when I turned the ignition the ?gen? light on the dash dimed like it normally does, but there was no clicking or anything else, just absolute silence. After 2 hours the car started like normal. The remainder of the trip, every time I stopped it would be 1 to 2 hours before it would restart. I self diagnosed myself with the classic hot start problem.

My understanding of the hot start problem is that solenoids heat up easily because they are exposed to extreme heat being mounted on starters beside the exhaust manifold. High temperature increases electrical resistance which prevents the starter?s solenoid from getting enough electricity. As electrical resistance is increased, either the solenoid can?t get enough electricity from the battery or it completely stops working. Without power from the solenoid, the starter is dead. The solution is heat shielding for reliable engine ignition. There are two types that can be used, a metal heat shield and a cloth heat shield wrap.

I purchased a starter specific cloth heat shield wrap from Heatshield Products and installed it. I simply wrapped it around the solenoid and starter and fastened it with the Velcro fasteners. I selected the heavy-duty cover which is double insulated for greater reduction in radiant heat transfer. I also purchased the metal solenoid heat shield that Ram Air cars were equipped with. It was supposed to fit any solenoid, but my mechanic told me it didn?t fit. I plan to continue pursuing a metal solenoid heat shield until one is installed on my car.

The next long distance drive was in October of this year, very cool. When I stopped for gas the first time, it wouldn?t start, total silence, lights and all electrical components working. After about 15 minutes it fired right up. The problem continued for the remainder of the trip.

While at my destination I had another mechanic try to diagnose the problem. He replaced the starter and this time I know it is a 2 post, high torque, stock appearing model. I haven?t been able to find much information about the difference between high and low torque starters. My understanding is that two posts versus one, coming out of the starter, is because they connect to more windings in the armature plus there are more pairs of field coils / magnets. So it builds a bigger charge from the battery enabling it to turn the engine over faster. He also replaced my cloth heat shield wrap with some Koawool S blanket and wire. He put that on the exhaust manifold and the side of the starter facing it. Koawool S blanket is rated for more than twice the thermal resistance as the Heatshield wrap, 2,300?F versus 1,100?F. On my return journey the problem was the worst it has been yet. 2 or more hours before it would restart.

Do you believe I have a hot start problem or could there be other causes? Do you have any suggestions as to what else I can try to remedy this problem?

When dealing with Chevy and Pontiac rebuilt starters, you might have to go through 6 of them before you get a good one…If there is “absolute silence” (no click when the key is turned) then it’s the solenoid mounted on top of the starter that’s causing the problem. Or the key switch or the neutral safety switch on the shift linkage…