I started a thread a couple of weeks back "pop pop pop.." whereas my car was running poorly, and backfiring. After trying several things, i replaced the fuel, and the car ran great....for a short time. Now its back to its same old problem. I know it has to be a simple issue. Here is my evaluation. I will summarize as best I can. Please feel free to comment:

Symptoms-
Runs very rough
Backfires under load or when rapidly throttling up from idle.
Backfires sometimes when key is turned on (like a free start - but a "free backfire" Blew out the muffler.)
runs same on batt or mag

Things I know-
plug wires good
plugs good
compression good
timer good
carb cleaned/needle valve good
coils good
no arcing under the hood
manifold gaskets good
head gasket good
fuel good
fuel line clean
fuel mixture setting adjusted
connections at switch tight
timer wiring looks good
hot air pipe on

My thoughts: Since its backfiring through the exhaust in a free start scenario, that means its getting fire at the wrong time, therefore i have an ignition timing issue. Since the coils and the timer are good, possibly carbon tracking in the coil box, or bad timer wiring? Am i missing something? Its almost like the firing order is screwed up, but its wired correctly, and for a short time, it ran great. Any Ideas?

Thanks!

Vince

Vince

You have my number, You can bring the car over when ever you like and we can trace the problem. I assume you want to go on the tour this weekend?

Steven

Have you rebuilt the coilbox in the past? If so look at the rivet holding the bottom contact strip. If it is loose it will cause intermittent contact. Just a thought

Replacing the fuel helped because it gave you a full tank, (I presume you filled it), which gave better fuel pressure, which temporarily overcame fuel starvation problem. You've since driven it more; less gas = less pressure = less fuel delivery through whatever your restriction is.

My guess would be valve timing or timer is set to fire while one of the valves is still open. Could be its cross firing because as you suggested, carbon tracking. Are the wires to the timer new? If not look for wires rubbing together and shorting.
Did you wire it so you have the correct 1243 at the timer and 1234 the coil box. It does sound like the timing is set too early.

Sure, I could be wrong but, try topping off your tank again as a test.

This is an interesting problem Vince. I can't figure why changing to fresh fuel corrected it for a while. (fuel cap vent?) Your exhaust backfiring does seem to indicate timing since the compression is good and therefore the valves are OK. Are you sure about the timer setting? About the only other thing you haven't checked, as you state, is the coil box condition. The fact that it ran good for a while also indicates to me that the cam & crank gears are aligned correctly as that wouldn't change. I'm stumped.

Not sure this was checked before but the pan bolt under #3 beneath the timer must be installed with the nut down, underneath the pan (the others should be nut topside) If its wrong, the timer terminal will short to ground at some advance position. Worth checking....Paul

Steve,

Thanks for the offer but i am out of time in the evenings. Had to cancel on the tour..There will be others. You guys should have a great time.

Don. Coil box is likely original. Jerry - only drove a short while. Tank is still almost full.
Mark - i replaced the original timer wires about 7 years ago. They look great...

Charlie - yes the timer is set correctly.

I am thinking more and more its carbon tracking. I think i will take all 4 plugs out, and lay them on the head and crank slowly with the key on to see if i get any erratic firing. Just seems to me its getting spark to a cylinder at the wrong time. When i short them to ground while running the problem persists.

Any way to spot carbon tracking?

Thanks Guys

Vince

Again, check valve spring tension. The valves move but there may not be enough tension to make them seat properly.

While I agree with you Jeff concerning the spring tension that problem wouldn't go away and return. The fact that it did indicates something changing causing the problem.

If it's a pre-26 model, you can run without the coil box lid and hold the coil points down one at a time and try to isolate a cylinder that way. Kinda like shorting each plug, but can be done while driving.

Vince, you asked:

"Any way to spot carbon tracking?"

Awhile back Ron said something to the effect that it is quite interesting to operate the motor in the dark at night...(or did John write that?).

Might be able to find your problem that way.

Good Luck,
Dave

I'm just thinking out loud here....If the problem is in the ignition, and the problem gets worse under load, you might try something like a spark tester on each plug wire. What I'm talking about is one of these deals that has an adjustable gap and you ground one end of it and put your plug wire on the other. It's not good for your coil, but maybe open the thing up to 1/4" - 3/8" gap, and with the other three plugs laying on top of the engine, turn the engine to a position where the spark tester coil is firing and look to see if any of the other plugs try to fire too. Do this for each cylinder. If you ever get two plugs to fire at the same time, I'd replace the coil box wood with a FunProjects kit.

Again, just thinking out loud. Forcing that spark to jump a wide gap can lead to internal shorts in a coil, so don't over do it.

Hal and others. Opening up the gap to 1/4" will perform the test you want but 3/8" gap is risky. I want to point out that laying spark plugs on the engine and watching them spark doesn't really prove too much other than perhaps the timer is OK. A weak coil can easily fire a plug gapped at the usual 1/32" gap when the plug is not under compression but is laying on the head. Likewise a bad plug can spark OK in free air but may not fire under compression. Clearly if you do see something erratic this way with your free air test you have found a problem but if this tests seems to prove that the plugs and coils are OK - NO NO NO it doesn't.

This symptom sounds like other cars sound when they have that darn large brass plate behind the timer which intermittently shorts out the timer. If that plate is in this car - toss it and the felt donut and put in a neoprene seal. If not that and you have good compression, I would have the coils checked by someone with a hand cranked coil tester. Even if not the problem, the coils being properly setup will make the car run a ton better once you find the real culprit.

Perhaps I should have been more clear. My idea was to put a large enough load on any one plug wire that the current would flow through a carbon track (If there is one) to another plug instead. I agree wholeheartedly that just because a plug fires across its gap in free air it doesn't mean it will fire under compression. I was just trying to think of a test that would identify a carbon tracking situation.

John,

They are Rons coils just redone. Extremely hot. May be why the problem is so pronounced if indeed it is carbon tracking. I dont think i have the brass plate..but i will check.
Time to remove the coil box wood and take a look at what i have. I know its likely original to the car.



vince

Hal, if you adjust the gap to over 1/4" you will "create" the carbon track you are looking for.

OK dumb thought. It was stated that all 4 plugs looked liked it was running rich. A spark plug will also look like that if it is failing, as it is not firing properly to burn the fuel. Been there done that on a car (not a T) that had 4 day old spark plugs in it that flooded then would not start. I had to change the plugs to make it run right. I was so stubbern that I cleaned the old plugs, re-installed them and then the car ran poorly again. those plugs hit the trash can.

Bill

Would an in line gas filter work with a full tank but no so good after you use some of the gas???

Doug,

You may be right.

Take a look at the inside of the coil box lid. If there are 4 shiny spots inside, you may have coils working up and touching the lid, causing an occasional cross fire.

Our '13 has a metal coil box and the darned thing nearly killed me a couple of times before I discovered what was going on. I insullated the inside of the cover and cross firing ceased and my arm is no longer covered in bruises.

Vince,

Be sure screen in sediment bulb is clear.

Ken in Texas

Keep us posted Vince. I'm very interested in the outcome.

Ken - screen is clear. Dave - no inline gas filter. Scott - i will check the box cover.

It will be a few days before i can get back to it but i will update this thread for sure.

thanks everyone for the input.

Vince

Vince, just to cover all your bases, you might ask a local priest to exorcise it...

Since all these things have been checked, and not found the problem, I would suggest that you find someone who has a good running T who would be willing to help you by swapping one part at a time. Such as replace one of your coils with one of his and drive both cars. If both run fine, then try another coil, until all 4 have been replaced. Do this with timer, spark plugs, carburetor and coil box. Check out the wiring for open connections or grounds. Especially around the timer. the timer rotates every time you change the spark lever position, so those wires in that area are constantly being moved. A broken wire, or loose solder joint or loose screw connection in that area could cause the problem. A bolt in the crankcase coming in contact with the timer could be the cause. Try a different either new or known good timer and also try your timer with another persons car and see if it reproduces the problem. Valves are also suspect. One valve sticking only when cold or after being parked with that valve open. If the spring is weak, it could only stick at times depending on temperature of the engine.
Norm

sorry, didnt read all of the posts, but w/a Ford timer they will sometimes fire on 2 cylinders at once. Also wonder if you're running on mag- sounds like mine when the magnets were weak

other thing is, there's spark and then there's SPARK- I had a carbon track in the coil box wood and the plug fired but not nearly as hot as the other 3

Vince,
You may want to take the timer off (leave the wiring in place) and clean any collection of metal filings out of the bottom. As they build up, if not cleaned out, they can cause a grounding of the terminals and cause misfiting of the plugs. It happened to me and blew out the muffler too.
Nick

Ok guys, here is an update.....I now know what is happening. Now to positively identify the cause.

I took all 4 plugs out and layed them on the head with wires attached. On battery, and slowly cranking through the firing order...and wala!!! Number 3 is firing at about half the charge all the time, and full charge during its turn to fire. All other plugs fire strong at the right time.

Is this a result of carbon tracking? Even if its not this morning i ordered a fun projects waterproof box rebuild kit, figuring it would be good to change it out anyway. I am glad i did. Here are some photos of my likely 89 year old coil box. Pretty rough.

If you are hearing a coil buzzing continously then you have a short in either the coil box wiring, timer wiring, or timer/brush itself. If you only have one coil buzzing at a time but seeing #3 always showing some spark when any coil is buzzing then you likely have some carbon tracking somewhere in the wood of the coil box. This assumes only that you don't have any plug wires crossing each other and leaking to each other which is doubtful since that would be easy to see in the dark.

Vince, what kind of timer do you have? I had a roller-style timer once that shorted out due to a crack in the insulator where the stud comes through the case. Also, there were several timer harnesses replaced on the O2O Tour a couple of years ago due to an internal short between the wires where they were buried in the loom. These were harnesses that had the Ford Script steel tag in them and they've been discussed (with a certain amound of disgust) on this forum.

You'd have to disassemble the timer at the #3 stud to see if it's shorting internally.

Yep, I repaired a 1920 recently with that same problem. The insulator on three on the timer was shorting out. surprised it didn't fry the coil.

John,

Coil is not buzzing constantly, but number three plug fires (weak spark) during the firing of the other three.
Warren - I have a rebuilt ford script roller timer - about a year old, but replaced it with another used but good timer with no change in results.
I have had the car shut down completely in the past (two years ago) when i got caught in a VERY heavy rainstorm, so having the waterproof box is an improvement no matter.
Carbon tracking would explain this i think. We shall see. If not...maybe its the tires??

Vince

Glad to hear you hit on something solid. Apparently the box is out and should be rebuilt in the best possible manner. (plastique)! Honestly I can't see anything in the photo but I suppose it could be on the hidden side of the wood. In any case you're on to something for sure with #3's "over exurberant" firing. Or supernumerary as the Brits might say.

Vince, looking forward to your report after the FP coil box rebuild. If it is carbon tracking, that will fix it. If it is the tires, you should buy some of these maybe?

http://www.flickr.com/photos/bruckzone/6070388625/in/set-72157627495859468

Vince, Let me see if I got this. You take out all the sparkplugs and lay them on top of the head. Turn the key to BAT and crank the engine over. #1 plug fires showing a good strong spark, BUT the #3 plug is also firing a weak spark. Correct? Turn the crank to #2 and the same thing happens? Seems to me current from the battery is energizing the correct coil at the right time AS WELL as somewhat energizing the #3 coil. This stray current is getting to #3 coil from the distributer or within the coil box. If you have #1 plug buzzing (#3 is also showing a weak spark) remove the wire from the coil box that brings power from the distributer to the #3 coil. If the #3 plug stops sparking, the stray power is coming through the distibuter. If the #3 coil continues to produce a weak spark, that coil is being energized from withing the coil box. Removing that one wire SHOULD let know where the stray current is comming from. (I say SHOULD because the more I learn about Ts, the more I realize how interesting they can be.

Gary:

I don't see how you can get any spark out of coil without operating its points. A small DC current won't pull the points open so no spark. It is not a case of a small current giving you a small spark. A distributor will give you a small spark for small coil current but not a T coil since it has its own points that operate from magnetism rather than a mechanical cam. It takes well over a few amps to pull the points open and only if you pull the points open will the coil fire at all. It almost has to be High voltage leakage through the wood or via the spark plug wires being near each other. I assume we are not talking about modern resistive type spark plug wire since that has its own set of problems.

Vince:

On rereading your statement about the coils buzzing. I realized you kinda didn't answer the question directly. What is important is that when you are pulling the crank through and checking each cylinder that ONE and ONLY ONE coil is buzzing at any one time even though #3 plug is showing spark each time some other cylinder is firing. Is that the case?? If 2 coils are buzzing at any time then that points to timer or timer wiring as I stated previously. I only one coil is buzzing at a time but 2 plugs are showing firing then that points to HV leakage via carbon tracking or spark plug wire leakage.

John,

Yes, only one coil is buzzing at a time.