Who Can Diagnose THIS Total Mystery? Win A Prize?
 

I'm new, inexperienced and at my wits end trying to resolve an issue that's about ready to make me walk away from my Model A, a '29 pickup. Even the best and brightest in our club (Gawd bless 'em for their patience with me) are shaking their heads.

The problem: The engine starts right up, runs cool like top all around town and will cruise at 45 mph cruise for miles until suddenly, with no warning, it starts to pop, sputter, lose all power and eventually just won't go. After it sits and cools for 10 minutes or so, it'll start right up, go on down the road and it should but then the problem is back, usually a little sooner than before.

What we've tried: First, we thought it was a carburetor problem, perhaps crap in the tank, fuel line or in the carb itself. We drained the tank, saw it had been coated and no sign of anything but a few flakes at the bottom and in the clear glass filter at the firewall. With those cleared out (gas bulb is now crystal clear) we also replaced the filter screens at the tank, shut-off valve, and at the filter. Again, it started right up and ran...for a short trip and started the same problem again.

At this point, we decided the problem must be electrical. We re-set the timing (even though it always started with one turn-over) and replaced the condenser. That SEEMED to fix it...but not for long.

At this point, we're thinking the time it took to replace the condenser allowed a cool-down that led to a temporary fix. So next, we replaced the coil AND the condenser. Same result.

When we noticed the wire between the coil and distributor seemed just a little lose, we replaced that, too, and assured secure connections at both ends. This time, she ran 110 miles on a club tour (mostly at 45 cruise speed) with 0 problem until....10 miles from home, the problem was back!

Other observations: There seems to be no real trigger for when this is about to happen.

When it starts misbehaving this way, twisting the choke rod to add fuel to the carb seems to have little effect. Pulling the choke rod out about two-thirds of the way (flooding it with gas) will cause it to sputter a little less and limp a little farther.

Following one of these "attacks," when you then shut off the engine, you can count to about 4 or 5 and there is frequently a single huge, loud backfire (always great for making a dramatic arrival!).

Engine temp is steady (and relatively low at about 170) but once the problem starts, things can (but not always) heat up. (The vehicle has a new radiator that works fine.)

At first, it seemed to happen after five minutes of sustained cruise followed by sitting at a traffic light for 2 minutes and then trying to start moving again...but that has not been a consistent pattern and seems to have gone away lately.

Early on, we thought the dreaded "vapor lock" was a problem because we've been dealing with this since it was 90+ degrees in the Florida summer. Now, it's 70 and we have the same problem and, as I say, the engine isn't overheated when the problem kicks in now.

Somewhere there's somebody who has had this same problem or knows how to fix it. I can't imagine what to try next...and I surely can't keep holding up tours and taking this thing on the road when I have no confidence I can make it there and back, short distance or long.

Maybe we should make it a contest and I could send a nice little prize to the first one who can solve this mystery? <grin> And if that doesn't work, maybe we'll have a drawing and the winner can take this headache off my hands! (Did I mention I'm now on my last nerve with this?)

This newbie sincerely appreciates ANY help/suggestions/thoughts and ideas.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

did you check the wire between the the top and bottom plate on the distributor.....it often causes intermitent problems.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Sounds like no gas cap vent or gas cap vent is plugged with something. Try running with no gas cap on your standard test run.

We had a '31 on the Natchez Trace Tour last Oct/Nov that had been fighting this exact same symptoms for many months. It was the reproduction gas cap. The vent was not open.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Well I would start by making it happen all over again and at the moment that the symptoms arise, do a little diagnostic work. First off, "just won't go" means different things to different folks but to me it means the engine stops running. At that point I would immediately (without touching/fiddling with anything else) remove the coil wire and hold it about ¼" away from a good ground source while someone cranks the engine over. The evidence of the jumping spark will tell a lot. During this same time I would feel the carburetor bowl and the fuel line for a temperature reading. If either is excessively hot, I would find the reason why.

Personally I suspect it to be electrical like a worn/loose wire inside the distributor. Ironically, when something like this comes into my shop, I first start checking for areas where "McGuyvering" has taken place followed closely thereafter by looking for reproduction parts. I have seen repro terminal box screws come loose and short out against the firewall, and I have seen poor quality wiring harnesses have loose terminal ends do exactly as you stated. I have never seen a situation that could not be solved when enough time & prudent thought were given towards the problem.

.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

I would send the pickup to me or remove the block on the firewall and insulate the back side. The repo-connetor blocks some times short through the rivets on the back and cause the problem you describe. The best solution is still to let me have the truck.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Check your valve settings
JIMI

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

I agree with Jim, the first and easy thing to do is remove the gas cap and try it. I've had this happen and found that crap [ technical term] in the cap would move around and plug the vent. A good through cleaning stopped the problem. Also make sure the fuel line doesn't protrude too far into the carburetor.
If thats not it, then look into the electrical issues.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

I would agree with Jim, Try another gas cap. I suspect your vent is partially blocked. The gas goes out slightly faster than the air comes in and creates a low pressure/vacuum in side the gas tank. The choke is simply cutting the air flow and creating a richer mixture for a short while and allows you to go another hundred yards or so.
Terry

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

I'll also suggest your gas cap. Right after it happens get out of your car, and untwist the gas cap. SOMETIMES when this happens you can hear the pressure release when you open the cap slowly.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Bad ignition switch, especially a rero switch that doesn't have a good positive click to the ON position.
Poor wire insulation on an original popout switch, so it's grounding out inside the steel cable.
Short wire between the upper and lower dist. plates grounding out or broken.
I assume the terminal box connections are clean and tight, and all wire terminals are soldered to the wire.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Thanks to all of you!

We considered the gas cap problem and removed the cap entirely...PLENTY of ventilation NOW but that does not resolve the problem.

Sorry, jhowes, not quite ready to ship it to you yet. We're on the road to a solution for this problem...somebody's got the answer!

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

sgwilson904, Check amp meter connections for looseness or melted plastic at terminals . If there is a open in the amp meter you can jump across the wing nuts on the terminal box as this will bypass the amp meter . Where is your battery ground connected? You might want add a ground wire from the frame to the transmission or engine block . Bubby Sharp in KY

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Thanks for your detailed description -- sounds like you have had some good advice thus far; however, what you describe sounds familiar with almost "any" vintage gasoline engine today.


One thing for sure, as opposed to voodoo, your Model A has something "unique" that others do not have -- just need patience to diagnosis it.

1. Diagnostic Test: Please try this "exactly" as spelled out below:


a. When engine sputters & "kills", (dead as a door nail), be prepared, already having a spark plug wrench and an assistant to stay in the car.


b. First, turn switch to "OFF" & "immediately" choke engine that won't start & allow engine to rotate about 15 revolutions with choke pulled. Hurry, because in 10 minutes according to your description, everything will be normal.


c. Next, immediately raise hood, immediately remove all four (4) plugs quickly to see if they are "wet" with fuel; & immediately ground & lay all four plugs on their sides, then turn switch to "ON" & have someone hit starter to see if all four plugs are firing.


d. If plugs were observed "not" to be wet, definite "fuel" problem; & if no fire at plugs, definite electrical problem. At least one can observe whether one has an electrical or fuel problem.


2. Electrical Possibilities: Coils & condensers used to almost last forever when made by Ford in America -- I have several old ones that look terrible with rust & corrosion; but, they still work -- today's foreign assembled or foreign made coils for vintage engines do not last as long. When either the coil or condenser heats up in use, some cease to function; but, after cooling off they begin to work again. As odd as this may appear, in "rare" cases, already experienced a "new" coil right off of the shelf that failed. Rather than commit suicide, if it were mine, (& would not have equipment to test same when hot), I would spend the less than $20.00 to try to eliminate this "rare" possibility & get another "new" coil & condenser. If that does not work, at least you are still living & can try the other fuel suggestion below.


3. Fuel Possibilities: Tank sealer? Your tank sealer may have worked in the past, but now we have ethanol in the fuel which can dissolve many older tank sealing materials. The big visible flakes you saw are noteworthy; but look at the orifice in a carburetor jet to determine how small a particle can cause an obstruction. One can buy 100% gasoline without ethanol at some stations, but on tour, one may not have this opportunity. Again, before suicide, take the screen out of the tank which can get clogged with dislodged tank sealer & try a NAPA 3039 fuel filter in the sediment bowl.

Hope this helps.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

H.L. Chauvin's suggests another "Dianositic tool", a can of starter fliud! When it is ready to stall, squirt starter fluid into the carb. if it still dies, the problem is electric, if not, it's gas. Good luck!
Terry

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

i would do the little wire between plates in the dist .

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

I would first tighten manifold nuts, then check the manifold gaskets and at the same time look for cracks in the intake manifold. I had a problem like this years ago and found that when the intake manifold heated up after several miles the engine would bearly run. come to find out it was sucking air when hot.
ran fine when it was cool. Changed gaskets and problem went away.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

i just had one doing that, and the cause was the nurex/modern upper distributor plate that someone put in. they have a poor connection design that takes the place of the wire. we replaced it back with an original style plate.
We used a conventional spark tester to determine it was electrical and not fuel. When the problem occurred the spark got weak and erratic.
whats the prize?

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

I experienced a similiar problem on my 30 coupe. It was the wire between the upper and lower distributor plate. The wire connector to the upper plate was installed incorrectly. The wire connector was so close to the metal surface on the upper plate that it would ground only after the the engine would heat the distributor. Also make sure this wire is the correct one, over the years they were replaced with the wrong type of wire. The incorrect type of wire will break over time with the movement of the upper plate while retarding the timing to start the car. Brattons sells the correct multi strand wire.
Another option would be to borrow a friends distributor for diagnostic purposes. If it solves your problem you have narrowed down the problem. The same goes for the carburator. It is always a good idea if you do much touring to have extra units (rebuilt and tested on your vehicle) on board.
Hope this helps you solve your problem.

Scott

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Funny story but similar symptom. When we were kids my brother put a crab apple in to the gas tank of dad's Model A. Dad would drive a week or maybe 5 minutes and the engine would suddenly die. Took dad a long time to figure out the problem as the apple would roll around and some times it would be exactly over the outlet shutting off the gas flow. Take a flashlight and check out the inside of your tank.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Could be a bad coil

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Thanks for the suggestions, Guys! Keep 'em coming...there's an answer in here somewhere, I know it! And I'm pretty sure it's not a crabapple in my fuel tank...still wondering if that brother survived Father's discovery? lol

Interesting suggestions about a bad coil which I got new from Snyder's. Apart from replacing it, is there any way to TEST a coil? Also, what about condensers? How would you test one of those?

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

I will say intermittent short, probably the distributor plate as mentioned several times; I'll be surprised if it's a fuel problem. I have always believed, and it has proven true in my experience, that most "carburetor problems" are electrical.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Simple.

A higher end voltmeter will usually have a capacitor test function. Or, you can purchase a capacitor tester.

The condenser in your car is basically a .25 uF capacitor. It should test at or near this value, and should show no leakage if good. Leakage is tested with an ohm meter (or a voltmeter with ohms setting).

When initially connecting the capacitor for leak test, the resistance (ohms) should be pretty low, but will charge quickly and show infinity (many megohms) and look like an "open circuit" within a second. if not, then it is leaky.

You can use a heat gun to heat the capacitor while under test and check to see if its value or leakage change with heat. If good- Its value should stay within 5%, and should never show signs of leakage regardless of temperature.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Check the voltage coming out of the generator. You could be overcharging the system causing the condensor and coil to get hot and cut out.

My two Cents worth. Tinbasher

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

We are having the exact same problems on this vehicle as we speak for the last few weeks and still cannot find the answer!!! But we are moving on!!! Been on here under "backfire" which it doesn't do DOUBLE THE PRIZE!!!!

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

In a way you are lucky to have a 10 minute interval where the engine dies which gives time for diagnosis.

No matter how many thousands of items are replaced, verified, adjusted, checked, tightened, cleaned, or repaired, please remember that the engine stalling end of the line is "always" in the combustion chamber.

The combustion chamber is like Harry Truman, mostly ignored; but this is where the Buck stops.

If one finds either an "electrical" problem or "fuel" problem where it really counts in the combustion chamber, & you are 50% ahead in valuable repair time & costs.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

as mentioned in my above post install a spark tester inline of the coli wire and observe the intensity and pattern when acting up vs running good to determine if the problem lies in the ignition

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Coil!

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Now thats a statement! I love it!

https://www.fordbarn.com/forum/attach...1&d=1359308872

And that is one sweet double!

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

I would drop the exhaust and try it , the muffler could be causing your symptoms .

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Bad coil. When it heats up it quits, then works when cooled a bit. Send it in for repair or find another coil .

My 2 cents worth.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Mine had similar problems. Overheated sometimes, a lot of backfiring. I pulled out the aftermarket screen in the fuel tank outlet after I figured out there is a screen in the top of the fuel bowl. I suspected that junk was being pulled against the screen choking off the fuel flow. In the end it was the carb float level being set to low. Henry's filtering system seems to work well. I wound up getting a quarter bowl of junk in the bowl.

Try this site. Good info!
http://www.model-a.org/troubleshooting_chart.html

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Check to see if at any point your fuel line is very close to the manifold or exhaust pipe. You could be getting heat from their at any outside temp which might cause vaporlocking.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

Would an overheated coil cool down enough in ten minutes to alleviate the problem and continue on down the road? I've never experienced a hot coil, so I am just curious.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

I always like Tom's ,what I feel are well founded diagnostic habits, and one thing I have learned is Test, Don't guess. I didn't see or read anything here if the coil was heated and tested. Possible breakdown after heating would cause the symptoms you describe. I also don't like parts changes with out testing the suspected parts that may be bad. If you suspected fuel delivery problems install a small auxiliary gas tank(quart or half gallon ) and go test drive. Heat can do funny things as far as resistance in circuits as well. Good Luck and DON'T walk away from a challenge!

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

I had a professionally restored popout switch give me the problem you described. I had to stop 3 times in 50 miles on the maiden voyage of my town sedan. I replaced the popout switch with the reproduction on-off switch and it has run fine for the last 16 years.

Re: Who Can Diagnose THIS Total Mystery? Win A Prize?
 

When it starts misbehaving this way, twisting the choke rod to add fuel to the carb seems to have little effect. Pulling the choke rod out about two-thirds of the way (flooding it with gas) will cause it to sputter a little less and limp a little farther.
__________________________________________________ _____________________________
If what you say here that pulling the choke helps, then it is gas not electrical. If it was electrical pulling the choke would have no effect.

Check and see if the gas line is in the carb or filter to far and blocking the flow of gas.