GT 500 - need your help with ideas on what could be wrong

[trotrof1]

Are we talkin cars or the brothel .

[557]

Both...

[csheff]

Jeff I suspected the coil but it ck'ed ok, will get one and try first.

[shelbydoug]

Coils can check good when cold. When the engine gets hot, they won't fire correctly. That's called an intermittent coil. You need to try a new coil to confirm. No other way to do it.

[Dan Case]

Is the ignition switch okay? I had one fail internally once in a 1960s Ford. Was the last thing I checked.

[shelbydoug]

Is the ignition switch okay? I had one fail internally once in a 1960s Ford. Was the last thing I checked.

+1. They like to fail in the run mode. So the car will fire up but then die as you release the key into the run position.

There are no outward signs and all you can do is use the shop manual procedure to test the switch.

I just threw out three of them. One was a recent failure this year. Why I was keeping the others, don't know.

So I've had the car since 1972. It's on it's forth starter switch and only has 23,000 miles. I think it's time that is the factor but I should probably stop hitting them with the 40# sledge hammer. 

[67350#1242]

One more thing to check - tachometer.  The run circuit passes through it.  An open tach will cause similar problem. You will have spark during crank but goes away during run.  The tach can be bypassed by pulling the leads and plugging the 2 harness leads together.
Kurt.

[Drew Pojedinec]

Coils can check good when cold. When the engine gets hot, they won't fire correctly. That's called an intermittent coil. You need to try a new coil to confirm. No other way to do it.

Have had the same issue with coil and other ignition components.
Driving fine and poof. Dead.
Fires fine cold dies hot.

Duraspark magnetic pickup would die this way too. Makes it hard to troubleshoot for sure.

[shelbydoug]

Coils can check good when cold. When the engine gets hot, they won't fire correctly. That's called an intermittent coil. You need to try a new coil to confirm. No other way to do it.

Have had the same issue with coil and other ignition components.
Driving fine and poof. Dead.
Fires fine cold dies hot.

Duraspark magnetic pickup would die this way too. Makes it hard to troubleshoot for sure.

This is largely a "coil in a can" issue. The newer style flame thrower boxes don't seem to have the issue but they stick out like a sore thumb on a "classic or period correct" set up.

It's no doubt shorting and grounding internally and maybe just boiling the oil in the can.

There are those that will claim the Ford yellow tops are the most dependable and you can't kill them. Then you will notice a box of them in the stash.


Some of these items are really ancient technology items. Like Shelby says "anything can happen. A blown gasket. A 5 cent washer."

Like with a Holley, a 008 o-ring goes and you could be on fire?


"You pays your monies and you takes your chances?" 


My Ukrainian Grandmother would always say, "OYE DUGGIE!". Now THAT'S grassroots wisdom!

[csheff]

Tried a new coil and still no start, seems like it wants to but no start. Going to have to dig a little deeper now. Will take no. 1 to TDC and go from there.
Where is the best place to buy the ignition switch that's correct? I will test that.  Trying everything  I can before tearing into motor.

[shelbydoug]

Tried a new coil and still no start, seems like it wants to but no start. Going to have to dig a little deeper now. Will take no. 1 to TDC and go from there.
Where is the best place to buy the ignition switch that's correct? I will test that.  Trying everything  I can before tearing into motor.

You have two choices on the switch. Motorcraft and Standard. Both I would say are very heavy duty and about equal. Either is still available from a standard auto parts store.

The only caution is that there is a difference between a '67 and a '68 switch. So just make sure you get the proper part for the application.

Make sure your connections are snug under the dash. I take out the ash tray and radio and just work through that space. That space is adequate.


You may want to take the coil wire out of the distributor cap and have someone turn the engine over. I always want to see the coil throwing the spark. Look out though. The spark hurts if it grounds through you. That I am highly experienced at. I had curly hair at one time. Now it's very straight.

[csheff]

Doug, what is the difference between the 67 and 68?

[shelbydoug]

Not entirely sure. I think there is an extra wire on the '68. I have both but haven't put them side by side.

Now you reminded me why I was saving the bad '68s. For comparison. It's on the list of things to do but you know what happens with lists?

[Krelboyne]

1967 ignition switch would have a threaded stud on the back.

[JWH]

I am sorry if I missed this in a previous post, but are you running points? Or Pertronix?