The Case of the Wretched Roadster

[David in San Antonio]

Any suggestions?
My Deluxe Roadster, last restored in 1957-59 ran great when I first acquired it in mid-summer 2022.
Symptoms: Recently it has to crank a long time before catching, runs rough, almost like one cylinder inconsistently cuts out, stumbles at more than about ⅓ throttle, stalls if left to idle and will not restart. The next day it starts again.
Smooths out when starter spray into carb.
I have zero experience working on Model A’s so proceeded under the close supervision of fellow Alamo A members and many packages from Snyder’s.
Equipment: 6 volt positive ground, generator, installed then removed Air Maze air filter, no oil filter, original style distributor.
So far:
Carburetor: Thoroughly cleaned and rebuilt the Zenith carb. No improvement. Switched to a rebuilt Tillotson which ran fine on another A. No improvement. Adjusted GAV once warmed up and running above idle to best result. Still running rough.
Adjusted idle mixture screw on carb while idling to best effect. Still running rough.

Ignition: New 6 volt Optima battery, new ground cable to frame which I wire wheeled until shiny. New correct gauge cable to starter.
Cleaned and rebuilt the distributor with longer lower plate pigtail, new condenser mounted next to the coil on the firewall. New (old style) points, new distributor cam, gapped points, observed hot spark through temporary clear distributor cap. Re-confirmed spark to all cylinders with screw driver from each plug to near the head while running. Nice bright spark and clear crackle sound.
Cleaned and gapped spark plugs. New high tension leads from distributor to plugs. New high tension lead from coil to distributor.

Compression: 60-80-80-80

Timing: Verified that the cam gear dimple is at #1 cylinder TDC by observing a wooden dowel inserted into spark plug hole while hand cranking.

Fuel: Drained gas tank, refilled with fresh gas. Replaced gas shut off valve. Old pencil filter was perfectly clean, no rust. New pencil filter. Verified that gas cap is vented.

Intake manifold/gasket: Sprayed WD-40 thoroughly around manifold to block area while running engine. No loss of RPMs. Then tried again with starter spray, no increase in RPMs.

Next step: ordered new wiring loom from generator cutout, new junction box, new wiring loom at junction box. Sections of 65 year old insulation crumbling or missing.

I’m tickled to have a mystery to solve. Not frustrated, just bewildered. I wanted a hobby when I retired and boy did my wish come true, living the Model A life.

Suggestions welcome!

[Chuck Dempsey]

Can't help, but Best of Luck, and welcome to the 'Barn......

[rotorwrench]

That number one compression makes me wonder about the valves on that cylinder. You may have a sticky one.

[David in San Antonio]

Thank you Chuck!

[David in San Antonio]

@Rotorwrench - I wondered about that too. How do I check if it’s sticky?
Prediction whether it’s intake or exhaust valve? I put a little Marvel Mystery Oil in the fresh gas just for superstition. Should I put some into #1 cylinder overnight then hand crank?
Also, I see you’re in San Antonio too. I’d like to meet you if you’re so inclined. I love learning.

[Jim/GA]

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Originally Posted by David in San Antonio

new condenser mounted next to the coil on the firewall.

Test each of these one at a time and test drive before going to the next one.

1) If the car has a fuse holder mounted to the starter, temporarily bypass it to take it out of the circuit and test drive again. Move the yellow wire from the wiring harness from the fuse holder straight over to the starter switch starter cable post. (Disconnect ground while doing this.) Test drive.

2) Move the condenser down to the distributor where Henry had it. Test drive. Also try a new condenser. (I have had bad ones right out of the box.) Test drive.

3) If you are using a pleated paper fuel filter element in your glass fuel bowl on the firewall, remove it and test drive without it. Use the original brass screen for the test.

4) Purchase a new "coil to distributor wire" from Bratton's with the ends soldered to the metal connectors. When installing this wire, make sure it goes FULLY up into the coil and down into the distributor cap. You may need to gently squeeze the metal ends in a bit, to make them a bit narrower, to slide fully into the coil and cap. You will feel a distinct click when they are fully in. Test drive.

5) With the tests you've done, you have not fully ruled out a vacuum leak. If you are down to this and are still having problems, remove the intake/exhaust manifolds, clean up the surfaces and put a new manifold gasket set in to ensure good seal there. If you are using "gland rings", make sure they are not bottoming out before the gasket is fully compressed. Also check manifold surfaces that touch the engine block for flatness and have them machined if required. Also look at the carb-to-manifold gasket surface, try a new gasket. Test drive.

6) You have one cylinder with low compression, relative to the others. Could be a burnt valve or a sticky valve. Worth investigating if you are this far down the list and still having a problem.

Good luck. Let us know what you find.

[David in San Antonio]

Thanks Jim. I’ll go through your list of suggestions. By the way, no fuses at all. Also no paper gas filter because it has a sediment trap on the firewall, not a glass filter.
I’m definitely having a Model A day! I have to laugh.

[Big hammer]

Just to add, do you have good fuel flow to the carburetor ? Some of us install a pencil filter in the gas tank and it could be clogged.

[rotorwrench]

The intakes can be easily seen through the spark plug hole. The exhausts are not as easy but all a person need to see is the edge of the valve to insure it goes all the way back down onto the seat. The exhausts tend to stick before the intakes do. Sometimes they will only hang up for a half a second but that's enough to be problematic. My old 29 set for a very long time and wasn't stored well so all four exhausts would open and then stayed that way. I had to pull the head to free them up but it was time to do a lot of work that I've been neglecting over the years anyway.

A person can do a flow check on the fuel system if it's suspect. Run about a half gallon of fuel from a makeshift line at the sediment bulb and watch it run for a while. If it has consistent flow then it is likely good enough to run. I've found that real fine corrosion particulate can make it through most screen type filters such as the pencil types. It doesn't take much to eventually get problematic but it takes time for that. If you've changed carbs several times then it may not have had that kind of time but it depends on how rusty it is. I'm in process of getting a relatively decent tank ready for my 29 since the old one finally rusted through. It's not easy to find good tanks these days.

[eagle]

Marvel Mystery Oil in gas will help with a sticky or slow valve(s).

[David in San Antonio]

Thank you Rotorwrench for your follow up. Thanks to Big Hammer and Eagle for your suggestions too. By the way Big Hammer, is your middle initial F? If so, your approach has been often utilized to great effect.

[nkaminar]

The one cylinder that is low indicates that there may be a leaky valve. To test the valves you can do a leak down test. This is basically pressurizing the cylinder and measuring how much pressure is lost. If the valves are leaking you can hear that in the intake manifold or exhaust pipe. If the rings are leaking you can hear that at the oil filling/breather tube.

Another test, much simpler, is to hand crank the engine with the ignition off. You can feel if the compression is low and hear any leaks, as above.

Running better with starting fluid sprayed into the intake indicates that there may be a fuel problem or an ignition problem. The starter fluid is much easier ignited. Try a partial choke to see if the performance improves, which would indicate a fuel problem. You can do a partial choke with your hand or the usual choke. Or you can try spraying gasoline into the carburetor. If a fuel problem is indicated, move the car outside and put a bucket under the carburetor. Remove the drain plug which is right under the main jet. Observe the fuel flow. It should be a strong stream. If not investigate the reason. It could be anywhere from the tank to the carburetor. Make sure there are no ignition sources around and have a fire extinguisher handy that is rated for gasoline.

[David in San Antonio]

@Nkaminar - Thank you for the leak-down test technique. I’m getting the idea that if a valve is intermittently sticking it is happening worst
when the engine is hot.
I will report the progress.

[updraught]

You can take the plug out and squirt a bit of very light penetrating oil at the valve stem. Should fee up a sticky valve. Lots of smoke produced tho when it starts so do it outside.

I'd certainly try a new condenser or two.

[David in San Antonio]

@Updraught - Thank you for the tip on freeing a sticky valve.
Also it’s mind-boggling that a newbie (me) in Texas reaches out and gets responses from all over the country and as far away as Australia! Technology in support of human kindness is such a change from my daily frustrations with balky printer cartridges and hostile medical insurance companies. Maybe there is hope for the human race after all.

[dave in australia]

Could be something as simple as a blocked fuel tank cap, causing low fuel flow. Try running with the cap removed. After sitting for years, bugs etc can get into the small vents between the threaded inner cap and the outer cap, or maybe you've inadvertently swapped the radiator cap for the fuel cap. Won't be the first time, and won't be the last time this has happened.

[David in San Antonio]

@Dave in Australia- Thank you for the fuel flow suggestion. Someone here in the USA said the world will not come to an end today because we know it’s already tomorrow in Australia. Clear thinking!

[shew01]

I love the title of this thread. [emoji23]


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[David in San Antonio]

Shew01 - Thank you. Sincere apologies to the memory of Sir Arthur Conan Doyle.
“By Jove, Holmes! You found the long lost Snyder’s catalog!”
The great detective made no gesture, no flicker of his eyes, to acknowledge the presence of Watson, his loyal chronicler.
“Hmmm” mused Holmes as he lit his meerschaum pipe. “A pigtail for the lower distributor plate which is longer than the original, Henry Ford part. Watson! I detect the evil hand of my arch-nemesis!,” Holmes bellowed.
Watson blanched and his cheeks puffed in and out. “Surely you don’t mean to say Dr. Moriarity? Why Holmes, you slayed that malefactor last year at the Festival of Speed Hillclimb. The deed was seen by 20,000 witnesses!”, Watson protested, aghast.
“I do mean to say it Watson. I always say precisely what I mean. Grab your overcoat, my medical bag, an adjustable spanner, a drift punch, my spare Zenith carburetor, a pint bottle of Marvel Mystery Oil, and a length of stout rope. There’s no time to tarry! The game is afoot!”

[shew01]

Not only can you turn a wrench, you can turn a word as well. Good job, ol’e chap. [emoji122]


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