MTFCA Forum

Car starts up and up and runs fine, then loses power & stalls out. Wait awhile starts up, repeat. Plugs look like this. Thoughts?[image][/image]

[image][/image]

Not my best post. Plugs are in order. Yellow tag is firewall

Your running problem sounds like a fuel flow problem. Clogged sediment screen?
You dont have a secondary fuel filter do you? @ this point, your plugs are a red herring.

You may want to check for an air leak at the back leg of the intake manifold.
Hope this helps,
Kevin

Will check both. Thanks

Once you clean them and see how they all spark when laying on the head, you can tell whether or not the issue is ignition, valves or an air leak.

RecklessKelly wrote: ↑

Sun Feb 02, 2025 1:25 pm

Once you clean them and see how they all spark when laying on the head, you can tell whether or not the issue is ignition, valves or an air leak.

Testing laying on the head doesnt mean they are firing under compression.
Better test is to short out one plug @ a time. If the motor runs rougher, the plug was firing. If there is no difference, the plug isnt firing or there is another reason the cylinder is dead.

That sounds like a fuel issue to check to begin with according to your post. Could be a fuel starvation issue caused by a stopped up sediment bulb filter, low fuel or mis adjusted carb. Pull the fuel line and see what kind of gas flow you have at the carburetor. If you think it’s the plugs buy a set of Motorcraft T plugs and see if you think that’s what it is. Don’t spend a 100.00 or more to buy a set of Champion X plugs yet. Motorcraft plugs work fine.
Don’t start pulling the engine apart until you check out the fuel issue first. T engines have been torn down only to find it was a loose coil box wire was the issue. When working on a T do the basic checks first.

Henry, Sorry for making a quick post but we were headed out the door.
I suggested you check for an air leak on the rear leg of the intake manifold, because the one thing that stands out to me is the condition of the plugs from cylinders 1 and 2, that appear to be running very rich. While the plugs from cylinders 3 and 4 appear to be lean.
In order to get the engine to run, we keep giving it more and more fuel to compensate for the air leak and end up fouling the plugs while others continue to be too lean. I don't think you have a fuel problem, because 1 and 2 are getting too much fuel. It appears 3 and 4 are not, and the common denominator in the equation is the intake manifold. The front leg feeds cylinder 1 and 2, and the back leg feeds 3 and 4.
Also, I would be wary of taking the plugs apart to check them, each time you remove the gland nut you run the risk of cracking the porcelain when they go back together. Better to take them out with the base. Just a thought.
Hope that better explains my thinking and gives you a place to start,
Kevin

Ignore the plugs. You most likely have a fuel flow/starvation problem causing your stall-out. BTW, it's not necessary, or even desirable, to remove the porcelains from the plugs. Just remove the whole plug without disassembling it.

Most T's have uneven coloration on the sparkplugs. Fuel flow through the intake manifold is not optimal or ideal, leading to richer buring in 1 & 2, than in 3 & 4. If the car runs fine, it's no big deal. Many people get needlessly hung up on this.

I agree with Jerry, there is no need to take the plugs apart. The copper ring gaskets are scarce enough without taking the plugs apart unnecccesarily.
The back two do look lean, and I would be checking the gland ring/seal on the back port of the inlet manifold.

Allan from down under.

Good advice. When reassembling the plug inserts to the gland assemblies on the head, about how much torque?

There is no torque spec, just snug down with a 7" long wrench, so that the porcelain isn't cracked by too much torque.

Porcelain breaks very easily! Do not over tighten them in the slightest amount. Fresh copper gaskets should squeeze very slightly. reusing copper gaskets should not be squeezed at all! Torque spec? Barely snug.

So the rear intake manifold seal is compromised. Is what's there a one piece gasket? Refurbishing that would mean exhaust manifold would have to come off too.