Problem: loss of power when heating up - clues for the cause?

[Hanno Spoelstra]

Took the F15A for a spin today.

Charged the battery, put in fresh gas, checked the fluids. All looked well and we took her for a drive. After about 10 min the engine started to loose power to the point I could no longer drive it. Could not see any problems. Let the truck cool down, it started right up. Drive off. When it heated up again, it lost power again and died. Let it cool down, started right up.

Parked the truck at home, did not have time to take a proper look and it will have to wait till later this week.

Meanwhile: clues, anyone?

Thanks,
Hanno

[maple_leaf_eh]

Vacuum leak, I suggest. (Not really based on much experience, but I know older engines have pressurization requirements and falling off partway into a drive makes more sense than a whole lot of other thing.)

The other thing would be a clogged fuel filter. My father's old car had that trouble. Let it sit for a while and the particles in the filter fall away from the element and allow fuel to flow.

[chris vickery]

Breakdown of the coil. Classic example. Old coils start to act up when hot and then work OK when cold until they are hot again.
Ford flatheads with the divers helmet dizzy are notorious for this one.

[Lynn Eades]

Yes, I would check Chris's suggestion.

[Yeo.NT]

It could be with more ethanol in today's fuels it's boiling off causing the dreaded vapour lock

[cliff]

Hanno change the coil and fuel filter first then go for a drive.

[Mike Kelly]

Hanno

If you remove the engine cover , then run the engine until it gets hot and the problem happens again. Then, remove a spark plug lead and get somebody to hold the lead near an earth approx. 5-6mm away , turn the engine over and look for a spark from the lead to earth . At least you can work out if its a weak spark problem . Mike

[cletrac (RIP)]

I'd bet on the coil. They did that quite regularly. Most people carried a spare coil.

[Richard Farrant]

No one has mentioned the condenser, they can give similar symptoms when they break down.

[Hanno Spoelstra]

Thanks all for the tips!

• Coil was new Bosch 6V approx. five years ago, so unlikely to go but will check (will not be before the end of this week).
• In-line disposable fuel filter is changed regularly, but will check again.

Other options:

• What about a bad condenser?
• Distributor cap: arcing inside the bakelite parts?

Methinks the distributor has to come off for an inspection.

Hanno

[Hanno Spoelstra]

Originally Posted by Richard Farrant

No one has mentioned the condenser, they can give similar symptoms when they break down.

Thanks Richard - I was just reading up on faulty condensers while I wrote my reply above.

Hanno

[Richard Farrant]

Originally Posted by Hanno Spoelstra

Thanks Richard - I was just reading up on faulty condensers while I wrote my reply above.

Hanno

Hanno,
A sure sign of a condenser failing is burnt points. They often fail when run for a certain time, then after cooling will run again. A common fault.
Also check your coil is connected the correct way around.

Richard

[Lynn Eades]

If you have to change the polarity of the coil:
I can advise that there was a thread on the Fordbarn forum where "Bubba" (Jim Linder)(a flathead dizzy specialist in the states, with the credentials) says the coil can loose 80% of it's original output capability, if it has its polarity reversed in service.

[Richard Farrant]

I should clarify, ensure the coil suits the polarity of the vehicle, there are both Negative Earth and Positive Earth coils, then ensure they are wired correctly. As has been said, the wiring reversed will reduce the output of the spark and not only that but the spark is reversed, this can cause problems in the distributor cap too.
Firstly I would go for the condenser, they fail more regularly than coils.

regards, Richard

[Tony Wheeler]

Originally Posted by Hanno Spoelstra

Methinks the distributor has to come off for an inspection.

Perfect opportunity to fit one of these Hanno, and forget about points and condensors forever!

[Hanno Spoelstra]

Originally Posted by Richard Farrant

I should clarify, ensure the coil suits the polarity of the vehicle, there are both Negative Earth and Positive Earth coils, then ensure they are wired correctly.

That's a good pont, will check that as well as the condenser.

[Hanno Spoelstra]

Originally Posted by Tony Wheeler

Perfect opportunity to fit one of these Hanno, and forget about points and condensors forever!

Good "point", is this a Pertronix unit?

H.

[motto]

Good advice Tony. 'Way to go' Hanno.
Hot Spark will be cheaper than Pertronix if they have a suitable kit. Pertronix have a larger range. Look at their web sites.

David

[Tony Wheeler]

Originally Posted by Hanno Spoelstra

Good "point", is this a Pertronix unit?

Yes it's the Pertronix kit Hanno. I bought mine a while ago but haven't got around to fitting it yet.

[Andy Mitchell]

Hi Hanno,

I had exactly this problem on a Fordson V8 WOT 2 a while ago ! Changed the condensor and cured the problem.

Cheers,

Andy

[Rhett Fisher]

Hi Hanno.
Is the power loss accompanied by misfiring and maybe bangs in the exhaust, or does it just seem that you're driving with the brakes on?
Rhett. :-)

[Phil Waterman]

Originally Posted by Rhett Fisher

Hi Hanno.
Is the power loss accompanied by misfiring and maybe bangs in the exhaust, or does it just seem that you're driving with the brakes on?
Rhett. :-)

Hi Hanno

Rhett asks a very good question, dose it feel sound etc like the engine is getting tight or purely a doesn't want to run issue. Example does it still spin over on the starter and cold start speed?

Does the temp gauge show normal temp when this happens?

Will be very interested to hear what the eventual solution to the problem is, or will it be one of those strange old vehicle maladies that problem goes away but you can't put your finger on what was the cause or that it really ends up being several small things combining.

Cheers Phil

[Rhett Fisher]

If there isn't any misfiring, I would probably discount any ignition problems. From my experience, the flatheads are very susceptible to wear in the fuel pump mechanism i.e. camshaft lobe, pushrod and pump rocker arm etc. Also, a likely contender is the pump diaphragm which might be damaged by this ethanol that's been foisted on us in recent times- I've had to renew the one in my 1936 Austin 7 recently, as the old one had literally crumbled to pieces! Plus I have two motorcycles which I now can't use, as their GRP fuel tanks have gone soft and leak like sieves. Arrrrgh!
Rhett :-)

[Hanno Spoelstra]

Thanks for all the input, will get back on this later (currently suffering from the flu )

[Phil Waterman]

Hi Hanno

That's it the truck has the Flu, same symptoms tired lack of power. But kidding aside hope you and the truck are feeling better soon.

Cheers Phil

[Hanno Spoelstra]

Hi Phil,

Indeed my cough sounds like a bad misfire

My local American car specialist did take the time to look up the modern equivalent of the condenser part (will list it later here), contrary to the FLAPS. It was not on stock but we be early next week.

To be continued.

Hanno