Engine won't start when it's Hot.
 

We ( my crew chief who is also my sweetheart and wife.) have a fresh Flathead built by "H & H Flathead" that runs great, but left us stranded in the middle of an busy intersection when it died and would not start. The temp gauge indicated 200 and it was correct. After cooling it down to 180, it started right up and we got it home. I might add, that it does not run hot on the road, but it was extremely hot that day, and we were caught up in traffic
The car is a 40' Ford Coupe that has been converted over to 12 volt with all new wiring,new battery,new gauges, all new electrical components,new grounds where needed,etc. The ignition system is a "Harman & Collins" distributor, recently rebuilt and tested by "Bubba's Ignition Service" ( he has been advised of this problem and is on board with us ) and giving a "good to go" It has two "Bosch Blue " coils, two "Echlin / NAPA # RR175 condensers, new points, new reproduction rotor and 2nd coil intermediate ring,new rotor, new cap, new wires, and new plugs. In our effort to find the source of our "no start when hot" problem we have purposely brought the engine up to 200 and shut it off, and tried to start it. No fire at the plug. Cool it down to 180 and she fires up immediately and runs great. Our trouble shooting has included checking the coils, condensers and the connections, temporary jump wire from the positive post on the battery to the positive side of the coil, still no start. ( cranks, but no start ) Each time that we duplicate this failure mode ( 200 degree temp) we bring it back down to 180 and she starts.! We are running out of ideas and would appreciate any and all suggestions as to where we go from here. We are excited and anxious to put some road miles on this New Engine in the the 40' Coupe, but right now, afraid to leave Home .

Re: Engine won't start when it's Hot.
 

Welcome to "Flathead Club". Mine does the same thing.

Re: Engine won't start when it's Hot.
 

Thank You.!! Been a member for some 62 yrs, but never experienced this before, that's why I'am asking for help.!!

Re: Engine won't start when it's Hot.
 

I think/thought mine was gas vapor lock. Maybe it it isn't.

Re: Engine won't start when it's Hot.
 

Just an outside thought, have you tried an external power source to the ignition? Maybe she cranks a little harder hot and the starter is dropping the voltage enough that the ignition won't produce a spark.

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Re: Engine won't start when it's Hot.
 

Could it be timing?

Re: Engine won't start when it's Hot.
 

It is possible one or both ignition condensers are going bad thermally I use Bubbas magneto condensers. Does the bosh blue coil need a resistor?

Re: Engine won't start when it's Hot.
 

Double check the spark plugs wire to see that they are on the correct plug. Have seen that before they the plug wires on the passenger side the two on the rear cross and the car ran pretty good no backfire. Take a screwdriver and ground out each plug and the engine should die down a bit. That how I found this problem with a flathead engine. A cheap test and easy to do.

Re: Engine won't start when it's Hot.
 

No fire at the plug. Cool it down to 180 and she fires up immediately and runs great. Our trouble shooting has included checking the coils, condensers and the connections, temporary jump wire from the positive post on the battery to the positive side of the coil, still no start. ( cranks, but no start ) Each time that we duplicate this failure mode ( 200 degree temp) we bring it back down to 180 and she starts.! We are running out of ideas and would appreciate any and all suggestions as to where we go from here. We are excited and anxious to put some road miles on this New Engine in the the 40' Coupe, but right now, afraid to leave Home .[/QUOTE]

When you jump the wire to the coil are you getting spark then, and no start, or no spark and no start? If no spark kinda of seems like coil, but they are hard to test when it is a heat related problem. Do you have power to everything else when this happens? I am not familiar with the ignition set up as far as having two coils, but I assume that is a normal set up. Is there some sort of safety switch/device that would activate at the 200 mark? Maybe something that you didn't know was there? I don't know how stock your rig is.

Re: Engine won't start when it's Hot.
 

This is a stab in the dark................ try using only one 12V coil and external ballast resistor (if needed) and the stock distributor set up.

Re: Engine won't start when it's Hot.
 

This problem is every week here. Get your self a coil and resister for a 1968 Chevy pu
If you have to many things on ign switch, jump direct to resister.

Re: Engine won't start when it's Hot.
 

"Vapor lock".? Yes this has all the makings of a vapor lock, and we definitely considered this. Still haven't ruled it out. The fuel system on this vehicle consists of a new steel tank ( Bob Drake ) New "Airtex" electric fuel pump (5 to 9 lbs.) steel line from the tank, filter, through the frame, up to the firewall to a fuel filter, regulator, short rubber flex hose ( 6" ) to the fuel block, and then to three (3) new "Stromberg" (England) carburetors, regulator'ed at 2,1/2 lbs. We are constantly on the look out for good fuel ( non Ethanol) in our area and make an effort to use it.

Re: Engine won't start when it's Hot.
 

This Engine came from "H & H Flathead's" with a "Power Master" Hi Torque starter on it, so cranking is not a problem.

Re: Engine won't start when it's Hot.
 

Timing is Ok.

Re: Engine won't start when it's Hot.
 

Yes, they could, but unlikely. Bubba is looking into this and has good luck with the "Echlin / NAPA" condensers. He has offered to send us two of the "Vertex magneto" condensers No, the "Bosch Blue" coil does not need a resistor

Re: Engine won't start when it's Hot.
 

My guess would be there is a crimped connection that the wire is broke in and when the insulation gets hot it breaks contact, when cooled down the insulation shrinks and makes the connection again, when running the current jumps the tiny gap. Especially with new wiring harness--they aren't fool proof. I had the above scenario happen. Good luck. rod

Re: Engine won't start when it's Hot.
 

When you jump the wire to the coil are you getting spark then, and no start, or no spark and no start? If no spark kinda of seems like coil, but they are hard to test when it is a heat related problem. Do you have power to everything else when this happens? I am not familiar with the ignition set up as far as having two coils, but I assume that is a normal set up. Is there some sort of safety switch/device that would activate at the 200 mark? Maybe something that you didn't know was there? I don't know how stock your rig is.[/QUOTE]

No spark,no start. Yes, power is good to everything else. This distributor is not a "normal set up" it is a "Harman & Collins" unit, that dates back to the fifties and was used by the Hot Rodders for more fire / performance. It is unique in its design, because it is actually two separate ignition systems housed within the same "crab style distributor" Two sets of points, two rotors, two condensers, and two coils. They work great and I am determined to use it if I can get it to perform like they use too.! This "rig" is not stock.
We really feel as though there is some sort of "safety switch/device" in the system, because that is the way it is acting, and it's working great, but there is not and I did not install one.!

Re: Engine won't start when it's Hot.
 

I have considered this, and am satisfied that the problem would probably go away, but I really like this "Harman & Collins" system and want to retain it. Replacing it is not what I'am looking for at this time.

Re: Engine won't start when it's Hot.
 

These new coils like blue there are many to choice from, electron ign,points coil, after market for vw and what ever else. There are lots of new old stock coil that can be used.
The good thing is when its time to have a few beers and wait to cool down, brag about your new parts. My lawn mover turn faster then that flathead.

Re: Engine won't start when it's Hot.
 

Are the coils mounted on the engine? Tooooo much heat will stop a coil. Might try putting them off the engine and see what happens. I have removed a coil from the engine to a cooler location with air flow. Your points opening and closing okay and not binding on their posts?

Heat can upset a coil. I have had to remount the coil off the engine to a location that is cool and better if the location has air flow. Might check the points for binding on their pivot posts when at 200 degrees and while your at it check the point resistance with an ohm meter at the same time. I have had this happen and corrected by increasing the spring tension on the points and lubed the pivot post. Fun@$%^&.