40 Ford Ignition Woes
 

My son bought a 40 Ford truck with a 59A flathead. It wasn't running when he got it. I put new points in it on my Sun machine and set the dwell. It started right up and ran well. We went for a ride and all ran strong. We drove about 5 miles and all of a sudden it died. No spark condition. We called AAA and got a tow home. He changed the coil and it started right up again. He took it for another ride days later and the same thing happened. Had to get it towed home again. What do you experts think is causing this?? Help please.

Re: 40 Ford Ignition Woes
 

Crab or helmet?

I have had problems with the HT side of the ignition. Cap and rotor can all fail under load, and run fine again until hot and loaded again. Have any spares you can swap on?

Re: 40 Ford Ignition Woes
 

Check to see if the balist resistor is not bypassed as this can fry a coil .

Re: 40 Ford Ignition Woes
 

with Mart crab / helmet or aftermarket also 6v/12v No such thing as to much information ??

Re: 40 Ford Ignition Woes
 

He changed the coil? More info please. Another coil from the cardboard box in the trunk?

Re: 40 Ford Ignition Woes
 

There are several items that with heat can go bad but when cold are OK. The ones mentioned above plus the ignition condenser.

Re: 40 Ford Ignition Woes
 

I put a Pertronix unit in a crab distributor on my engine because these reproduction parts are so terrible.

But, if I were doing a stock ignition all over again, I’d buy a coil from Skip Haney and a condenser from Tubman.

Re: 40 Ford Ignition Woes
 

It's a crab distributor. I think the resistor has been bypassed. I will have my son check it out tonight. Will let you know what we find. Thanks!

Re: 40 Ford Ignition Woes
 

Did that with my helmet distributor. VERY SATISFIED! Car runs really strong and reliable. I'd be confident using it as a daily driver. Bought 2 each so I'd have spares. Also bought NOS resistors and points on evilBay for spares.

Re: 40 Ford Ignition Woes
 

something worth checking is how the points fit on the pivot post, I just had one set of points lock up when it got hot so the 1 point was locked open so the distributor had no spark, was ok & tested good when it was cold but after driving for an hour or so the 1 set of points locked up, I have just drilled it out to give more clearance

Re: 40 Ford Ignition Woes
 

Condensor condensor condensor

Re: 40 Ford Ignition Woes
 

Where were you buying your condensers?

Re: 40 Ford Ignition Woes
 

Changed the condenser, same thing happened and needed another tow.

Re: 40 Ford Ignition Woes
 

The resistor is bypassed but we are running a 6v coil that doesn't require a resistor from Napa.

Re: 40 Ford Ignition Woes
 

The first thing I check when a car just stops as check if an ignition or gas problem. Take off the air cleaner and work the throttle to see if the accelerator pump squirts out gas. If so fuel is not a problem. Then pull a wire and hold it close to ground as you try to start. You should have a hot blue spark. With a crab distributor you have an external coil. So check the output of the coil with the spark test. If still nothing you know it is in the ignition upstream of the coil. Check the input voltage at the coil. If not there keep going back.

Re: 40 Ford Ignition Woes
 

Flaky ignition switch...

Re: 40 Ford Ignition Woes
 

We checked for a fuel problem and getting a squirt. No spark though. Next time we take it out, I am bringing a hotwire and a multimeter. Thanks!

Re: 40 Ford Ignition Woes
 

just wondering where is the coil mounted had nothing but drama when i went back to a crab turns out the coil was overheating when mounted on the eng moved it to the inner guard problems solved you couldn't touch the coil it was that hot but now gets warm but you can hang on to it

Re: 40 Ford Ignition Woes
 

We worked on it again last night. Put another new condenser and coil from Napa on it and as usual it started right up. We drove it about 50 feet and it died again. Pulled a plug and checked for spark and none. Turned key on again and checked voltage on the - side of the coil. 6.2 volts present. In my estimation, it has to be the cap, rotor or distributor. What else can it be?

Re: 40 Ford Ignition Woes
 

Check the ignition switch at the steering column. Take it off and check the contacts. They get corroded and burned and cause a high resistance.

Re: 40 Ford Ignition Woes
 

Good call Ken.

Re: 40 Ford Ignition Woes
 

You can eliminate the cap/rotor by checking the output of the coil. No spark there (along with no spark at a plug) says it is not a cap/rotor problem.

You have 6.2 volts at the coil. What do you have at the points side. Steady 0 would imply that the points stay closed, while 6.2 volts would imply that the points remain open. Assuming you have an analog meter, a slow crank speed should show some needle movement that the points are opening and closing.

Re: 40 Ford Ignition Woes
 

I put a jumper between the neg battery post and the neg side of coil. Still no spark. It's frustrating because the system is so simple. I am looking to the cap and rotor next.

Re: 40 Ford Ignition Woes
 

I'll check that next with my old Simpson analog meter. Thanks. Points are new and set up on a Sun machine but still could be the problem.

Re: 40 Ford Ignition Woes
 

Cap, rotor or wires.
These have caused me trouble before.
I mentioned it in post #2.

I replied having only read page 1.

If you have pos ground and touch a neg jumper to the neg side of the coil it probably won't generate a spark.

You need to have a constant neg feed to the coil and intermittently connect between the pos terminal on the coil and ground. It should generate a spark as you remove the contact with the ground.

Re: 40 Ford Ignition Woes
 

Where is the best place to buy a new cap and rotor for the 47 crab? I think that is the problem.

Re: 40 Ford Ignition Woes
 

Thirdgen auto is the go to place. Michael is very helpful.

Re: 40 Ford Ignition Woes
 

be careful. The "crab" cap with the wires exiting sideways is (something like) 41-42. A 47 cap would be the rabbits ears type cap. The rotor arm is specific to each type.

Re: 40 Ford Ignition Woes
 

Does this mean either type is ok for the 47 crab as long as you run the right rotor for a given cap?

Re: 40 Ford Ignition Woes
 

Well, what I was really getting at is what type of cap do you currently have? If a crab type, you need the crab type again. If a rabbit ears type, you might want one of those, but might want to go to a crab type for simplicity.
The term "47 crab" in not strictly correct. In 47 the distributor was the same as the earlier ones (true crab type) but was modified to take a new cap, which is nicknamed the rabbit ears type cap.
From an ease of fitment point of view, the earlier crab cap is the popular choice.
Mart.

Re: 40 Ford Ignition Woes
 

The 47-48 has a two piece cap… a real pita to work on. The 42-46 has the crab type cap that many prefer. The only difference is the cap, rotor, and retaining clips. We offer all three items all made in the USA

Re: 40 Ford Ignition Woes
 

I'm no know it all but what I'm seeing and hearing here is a loose or corroded connection heating up and losing continuity. I would start at the battery and work my way to the points cleaning and checking resistance at each and every connection. I had a little experience with this when I bought my 41 pickup. It took me awhile but I found it. Tim

Re: 40 Ford Ignition Woes
 

OK. Unscrewed the switch from the lock. How do you check the contacts? Looks like you have to open the case. How do you do that without destroying the switch? This is a 1941. Don't know if that makes any difference.




https://www.fordbarn.com/forum/pictu...ictureid=47662

Re: 40 Ford Ignition Woes
 

That switch is different from the 40. I’ve never taken one of those apart. Maybe someone here has done it .

Re: 40 Ford Ignition Woes
 

Do the mounting holes go side to side or top to bottom?
I have NOS of both types. I could mail you one to see if
it makes any difference.

Re: 40 Ford Ignition Woes
 

Thank you for the offer. That is very kind. I will keep it in mind as I try to crack this nut open.

Re: 40 Ford Ignition Woes
 

confusing post since there are two people asking for assistance.

Re: 40 Ford Ignition Woes
 

I’ve taken the 41 switch apart. Not hard . Drill rivets , be careful the spring inside is small plus a 3 sided contact plate. Clean both contact surfaces and I use super glue to temporarily hold the pieces together while I use small screws or rivets to reassemble.
Before you go through all that , you should check resistance through the switch at each of the 3 connections .
Another issue may be how many amps you have going through the switch at each. It wasn’t meant for much

Re: 40 Ford Ignition Woes
 

Another vote here on the ignition switch. Mine would heat up and the game was over. Bypass the ignition switch completely and see what happens

Re: 40 Ford Ignition Woes
 

The contacts in the switch aren't robust enough for much amperage draw. A good fix (in my opinion) is to install a relay to power everything up through the switch. Going this route, removes the load on the contacts. The switch now only activates the low amperage relay coil.