Model A running issue
 

Hello All,

I am having an issue with my Model A. I have rebuilt the distributor and re timed my car twice now. I tripled check the point gap and all is ok. However, after driving for about 35-40 minutes the car starts to lose power and backfires regularly. Any idea why this might be? Is it the points, timing, condensor, etc...?

Thanks
Alex

Re: Model A running issue
 

First post Welcome to the barn ! When it starts losing power and backfires it sounds to me like your not getting enough fuel flow, remove the gas cap when this happens

Re: Model A running issue
 

Or Manifold leak??

Re: Model A running issue
 

Years ago, I had a similar problem. Car would run fine for 20 to 30 miles and than misfire, just barely run, and no power.

I would check everything including cleaning the spark plugs, which were just replaced. Car would run great again for 20 or so miles and than problem would come back.

Problem ended up being “wrong plugs”. Vendor had sent us the incorrect spark plugs. I installed correct plugs, everything was fine.

I would check your plugs. Are they correct? Are they old and worn out? Is they gap correct.

Good luck.

Re: Model A running issue
 

Coils and condensers, that are in the final stage of life, tend to work fine when cold but fail when they get warmed up.

Re: Model A running issue
 

My first thought after reading your intro was the same as Big hammer's. Loosen the gas cap and drive again as he said. It only takes a couple seconds and it's non invasive. If this is happening under acceleration / load conditions, open the GAV. Backfires through the carb are usually lean conditions, but backfires through the muffler and exhaust system are rich conditions.

That said, I've read from knowledgeable folks on this forum that 95% of driveability issues are electrical. That seems to match my experience with the A. Your symptoms would be consistent with increasing heat and or vibration as was also mentioned above. The Model A ignition switch is known to cause backfire / irregular popping noises when it is worn out. Try jiggling the key up and down, in and out a small distance and on and off etc.

Re: Model A running issue
 

If everything else checks out it would be worth checking the valve lash. My problem was rough idle after warm up. After a major valve lash adjustment (some were way too tight) it ran great and still does five years later. Let us know the fix.
FL Panhandle (hello Helene)

Re: Model A running issue
 

Hello, condensers are a known trouble spot, some of the newer repro are worthless, the location of the condenser gets hot and breaks down, there is a kit to relocate on the point plate to get it away from the heat . Snyders,among others sell it .

Re: Model A running issue
 

Since the problem only happens after the engine warms up, as others have said, change the condenser. If it still has the problem, change the coil.

Re: Model A running issue
 

Most likely your condenser is going out or the coil.

Re: Model A running issue
 

x5 first concern is condenser!.....modern repros are notorious for these symptoms when they get warmed up.

Re: Model A running issue
 

To test the condensor, change it out. If the performance does not improve, it was not the condensor. To test to see if heat is causing the coil to fail, cool it down with some ice or the spray cooler use in electronics.

Re: Model A running issue
 

When I bought my car the condenser was attached to the firewall on the other side of the bracket that holds the coil. I was told this location was believed to be lower temperature than inside the distributor. It worked fine, though I have no data re temperatures nor the electrical difference of remote mounting.

Re: Model A running issue
 

Mounting the condensor near the coil is probably a tiny bit better than down at the points. The coil and condensor work as a team to generate the spark. It is called an LC resonating circuit. If the LC circuit is working correctly there is no or very little arcing at the points.