Random No Start?

[Ol Blue K20]

Originally Posted by Sheepdip

I have heard all the debates over the years as to if this fix is right or wrong the only answer I have is it works!

Example: My 40 Ford coupe I built as a frame off, every thing was new ...battery cables, wiring was a quality kit, grounds galore, battery to engine, engine to frame, frame/engine to body, dash etc.

I used a high torque mini starter with fender well headers so the heat is theoretically away from the starter, but these old Fords are known for the hot engine compartments from lack of air flow. I had heat soak issues develop within a week of getting this car on the road.

I used the Ford solenoid trick and it has started every time even on 100 degree days and running the A/C

Just my experience

I agree 100 percent.....

[Boog]

Originally Posted by ga-stepside

The problem is as the heat goes up the GM solenoid gets hot and requires more current to activate it. The small purple wire coming from the ignition switch can not carry the required current. Using the Ford solenoid and a larger gage wire for the GM solenoid fixes that current issue. You could change the purple wire to a larger one but the ignition switch is not made to carry much current and would likely fail.

^^^^^^^
Now this makes sense. So it is more an issue with secondary wire gauge from ignition switch to starter solenoid experiencing voltage drop due to under hood heat rather than positive battery cable voltage drop from battery to GM starter solenoid. This is what lost me. I knew power from the ford solenoid still had to go through the GM solenoid to engage the starter drive. Thank you.

[franken]

There are believers in the idea that hundreds of millions of GM vehicles used the same starters and wiring and they worked, which they did, and there are those who don't.
Fix the underlying issue and the solenoid will work. Typically, the underlying issue is bad wiring and/or poor connections, or worn out (resistive) switches in the circuit.
Of course, a bandaid solution is easier than troubleshooting so it's popular.
Yes, it's a bit of a long path from the battery to the solenoid, but I've jumped solenoids with a 20G or smaller jumper, so it doesn't draw that much.

Measure voltage to the block and to the battery from the S-terminal.

[schovil69]

Just dealt with a similar issue on my Dad's '70. His truck's issue was a wiring problem.
Turned out to be the ignition wire between the ignition and the coil. A wire loom mounted near the top of the firewall carries it across the engine bay. The wire had broke in two inside the wire loom. The problem did not recur after splicing the wire back together.