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@$%^&.

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

Coils do not like heat. Try locating the coils off the engine in a cool place with air flow. Also check the points for binding on their pivot posts at 200 degs and while your at it check the point resistance with an ohm meter. You may have to increase the spring tension on the points and lube the pivot posts. I have experienced both of these conditions. Fun@@#$^&.

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

Yes, the coils are mounted on the Engine. Up front, but up high. Checked them with a laser heat gun when it's running and they registered 170. Will check the points. Thanks for the suggestions.

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

I'm not sure if I can help any but this a harman collins set up, right? Correct me if I am wrong, but isn't this two separate 4 cylinder ignition systems? If you had said it only runs on 4 cylinders, I could believe that one of the sides of the ignition system has failed. As it does not fire at all, we need to be looking at something that is common across both ignitions.

Are you 100% sure it is a non start due to no spark? Or could it be a typical over rich problem, or vapour lock? I'm familiar with over rich situation in 94s but have never ran a stromberg. I have not experienced vapour lock.

Next time the non start situation arises, connect one of the plug leads (or one from each side of the ignition) to a spare spark plug and see if it sparks.

I'm wracking my brains trying to think what the problem might be, but other than the above, I can't think of anything.

Mart.

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

Newly rebuilt engine, lots of fresh paint. Condensors mounted on a nicely painted bracket.

It is possible that you have a poor ground that fails when hot. The condensors need a good ground. Both being faulty? Failing at the same time? Not likely. But a common ground failing ... maybe. I'd be checking that bracket, assuming you have one, for good grounds.

(I know that on a stock distributor with a loose mounting bolt that grounds the condensor can make you scratch your head.)

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

Do make sure the bracket for the condensers is held tightly to the vacuum brake adjustment nut. Bubba sometimes leaves the nut loose for you to adjust the brake. Also the vacuum brake adjustment assembly to the distributor body should be tight. Are you using the 40 Ford ignition switch? H&C want both coils to be fed from two separate wires back to the ignition switch. They wanted 12AWG for 6V coils (at least) I would suggest #14 for 12V. Make sure the ignition switch is fed from #12 wire back to the circuit breaker and all the connection points are tight.

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

There is one common problem when going to 12 volts, you must bypass the resister under dash. With 2 coils feeding from 40 ign switch, maybe better going to key start.
Could it be you are wired to a circuit braker
If you had a alligator clip put the coils direct to battery.

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

"Bubba sometimes leaves the nut loose for you to adjust the brake."

Poor Bubba. The cost of fame.

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

You are right about the "Harman & Collins" ignition system. It is two separate systems by design, and it will run on four, but not now.

Yes, the no start mode is no spark. Haven't ruled out the vapor lock possibility, but right now, we are looking for fire at the plug. Using a spark plug tester in line and it indicates no fire.

Appreciate your input.

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

If it were me I'd replace the HC setup with a regular distributor and try it, if it fires up when hot then you have isolated the problem to the HC unit, if it doesn't fire then look at the coil and the wire from the coil to the distributor.


Just my $0.02 worth.

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

You have a good point.! I have been guilty of too much paint in the wrong places, and I will certainly look into this. Unique to the "Harman & Collins" system they do have their own bracket for the two condensers.

Appreciate your input.!

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

I think this is a good idea. Several times, I have been able to finally find a pesky problem by swapping in a known good unit. As a matter of fact, I'm in the middle of just such an exercise right now concerning (O/T) Quadrajet carburetors.

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

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

This is good info, I will be looking for a loose nut.

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

Appreciate your $.02 worth. Check my reply on post #18.

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

Us do it yourself's are guilty of parts swapping, and I am one of them,but at this point I am trying to retain this ignition and isolate the problem,instead of replacing it. I have a fresh stock distributor on stand by, if all else fails.

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

The first thing you have to do in a case like this is define the problem as precisely as you can. That's what swapping the distributor is about. There have been mentions of vapor lock, ignition switch wiring, and I don't know what else, so it sounds like no one is really sure where the problem actually is. I don't think anyone was suggesting permanently replacing the H&C, but you have to find out if it is the problem or not.

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

Agree. Swap as a diagnostic step, not total abandonment of the HC unit. If the fault persists it is not the HC unit, if it goes away it is.

Mart

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

You measured coil temp at 170 degrees - motor at 200 degs at same time? Have you cleaned the contacts in the ign switch? When the motor is at 200 degs check the continuity of the primary and secondary of both coils. I think 170 deg coil temp is very hot to the touch! Engine runs fine until it rises to 200 digs I am assuming and if so the problem is heat related. If those coils were mine, I would find a cooler place for them.

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

Steve, the way you have both coils fed from one wire, if either coil shorts when it gets hot it would likely disable the other one due to there being a large voltage drop. You might try removing the wiring feeding power to the coils (leave the distributor side of the coils connected) and then feed both coils directly from the battery with individual leads. If one of the coils fails, you should continue to run on four cylinders. since the good coil would still have power directly from the battery.

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

Appreciate your suggestion, and I have definitely considered this. My crew chief has also suggested this, and I agree that this would be a way to isolate the problem. Just wanted to clarify that doing away with the H&C distributor is not an option at this time. I have swapped this before, and am willing to do it again.