39 coupe
 

Hi Guys

dual edelbrock 94 carbs (rebuilt by Charlie few years ago)
Bubba 11A distro
Skip coil
Electric fuel pump (manual pump removed)
New plugs
New condenser


Car started right up after sitting over a week. After warmed up and driving it started bucking on me bad. I made it back to the garage. I thought it was fuel related. I pulled the fuel hose off to carbs and turned on switch to the electric pump and it was pumping fuel. I then took the air filters off and put carb sync on both carbs and they were perfectly in sync. The car idled nice, but at higher RPMs it was breaking up. I began to move the vacuum line (in the Offy manifold to distro) and the car stalled. It now will not restart. I could be wrong but I don't think the vacuum line would prevent a restart.

I am now thinking maybe spark plug wires?

Please note, I already changed the condenser....

looking for your ideas......

Re: 39 coupe
 

New condensors have been known to be bad.

Re: 39 coupe
 

If it was vacuum on the line when you pulled it, the points plate shifted and lost connection or ground inside.

Re: 39 coupe
 

Step one: pull a plug wire and see if it will jump half an inch with a nice blue spark, when cranking. If not, start at the coil; should have battery voltage with the points open, and about 1/4 less with the points closed (~6.0, ~4.5). Best to turn the engine over by hand (wrench on crank nut or rock the car in high gear, coil secondary (high tension) pulled out).

If no voltage at the battery side of the coil, work back through the ballast resistor and ignition switch to the battery to find the loss of voltage.

If low voltage and not jumping up and down when cranking, disconnect the coil wire that connects to the distributor and see if the voltage comes up to battery voltage; if so, the points are stuck closed or the wire or condenser is shorted to ground.

If battery voltage at the coil does not drop when turning engine to close points, the connection to points is bad; wire broken or bad connection at coil to distributor wire, or more likely points not closing or burned/bad contact at points.

Good luck!

Re: 39 coupe
 

Thanks for the very detailed advise. I’m by myself so some test I am unable to do until I have a friends help.

I put a volt meter on coil. Turned on key and got 6.1.

I had a spare coil & condenser and switched out the ones on the car.

Still cranks strong but won’t start.

Re: 39 coupe
 

Just to check for fuel. Air cleaner off, Look down carb while operating accelerator. To verify fuel delivery bown carb barrel.
Have had similar non start but with electric fuel pump this normally takes care of the " empty float chamber at carb " for non start.
Phil NZ

Re: 39 coupe
 

Here's a handy device for just such occasions: https://smile.amazon.com/Ram-Pro-Eng...0485488&sr=8-2
But, of course, it only works if the engine starts:(

Re: 39 coupe
 

$3.99 @ Harbor Freight.

Re: 39 coupe
 

Three different coils and condensers. It started with the original skip coil. Ran great in am. Just took it out again.....bucking bad.....ugh...

Re: 39 coupe
 

Try another distributor, if you have one.

Re: 39 coupe
 

Whenever I have a symptom such as your's one of the first things I like to do is throw a jumper wire from battery to coil, to remove doubts of faulty switch. Best of Luck

Re: 39 coupe
 

Stick to the skip coil. Bucking under acceleration, if all is well ignition and runs idle. flood it with mmo (or whatever you got, diesel fuel has some lube to it) and drive the shit out of it. repeat. sticky valves. it happens. Valves are hard to see, if idling well might be something to consider. Valves can be finicky under load.


if 6.1v at coil you burning up stuff. 4v


Pull the choke when accelerating for lean condition (or a cold motor). At least it will tell you if fuel delivery is low then, if it accelerates and doesn't buck. It won't run great but it wont buck.


I'm guessing valves...





.

Re: 39 coupe
 

Thanks guys. I tried pulling choke when it was happening and it made no difference.

Yesterday I took both carbs off. They were rebuilt by Charlie a few years ago. They had some black particles in the bowl. I pulled out float needle and the fuel mixture screws. Shot them with carb cleaner and then air. It’s all back together today I’ll tune them and test drive.

If it still occurs, I’m thinking my next step I’d pull distro and change points and rotor.

Prior to all this, I did do mmo in tank and down carbs. I can always do it again.

The wire from battery to coil. Please tell me more. Is it merely adding a jumper from positive (neg battery term). Also if it corrects issue, what does that tell me.

Re: 39 coupe
 

If the jumper corrects the problem, it points to the ignition switch or the resistor unit under the dash. I had the ignition switch go bad on a '36 I had years ago; took it apart, cleaned it up, and was good to go. Also the word is that repop resistor units are by far inferior to original Ford units. Which do you have?

Re: 39 coupe
 

Thanks Tubman. I have an original resistor.

When doing jumper to coil. Do I need to disconnect any of the existing wiring?

Re: 39 coupe
 

Nope. You are only duplicating the existing ignition circuit, just eliminating any possible points of resistance. Remember though, that this jumper is a temporary diagnostic tool.

Re: 39 coupe
 

TY Sir! I’ll keep wittingly it down.

Just sitting here thinking. I only am running an airtex electric fuel pump (removed mechanical) another possibility it that not running 100% and cutting out.

Re: 39 coupe
 

If you do the jumper lead as suggested and the engine starts and runs well....Do NOT leave that jumper wire connected very long! If this seemingly solves the problem, shut the engine off and determine which component, that you bypassed, is at fault.

Re: 39 coupe
 

Although it's true that some of the repop ignition resistor's are inferior to the originals, I've also had original resistors fail with high resistance connection crimps to ends of the nichrome wire heating element that have intermittently acted like an open circuit, and I've also had the wire element with either shorted turns or completely burned open on original ignition resistors.

Re: 39 coupe
 

Will do as suggested by you and Tubman. It will only be on to test out.

I’m working my way down the list.

1 carbs cleaned and reset - need to finish that this am
2 jumper to coil
3 points and rotor

It’s not the pump. I recall now when car would not start I verified it was pumping fuel to carbs.