'Skipping Cylinder' or 'Is This Safe?'

[CatGuy]

I'm trying to chase down a 'missing' or 'skipping' on my '26 under load. It runs pretty good at idle, decent, anyway. However, once starting out it has a very noticeable 'miss' in both low and high. While researching the "Model T Ford Car" book from Page it suggests this action. Won't that hurt......or at least cause me to wet my pants??

[Scott_Conger]

you won't be shocked like you think
you won't be shocked at all, unless you have a coil box that needs rebuilding, and even then, you'd have to touch the coil box itself. Vibrating points never bit anyone (there is no high voltage up there)

[CatGuy]

I assume the test results would be that if the one left to run kills the engine that's the dead cylinder?

[speedytinc]

Short out 1 spark plug or 1 coil @ a time. If there is no change in the missing(should get worse) thats the bad cylinder.

[Norman Kling]

Some misses only happen at higher compression, so would not be noticeable at idle or light throttle, but when pulling with open throttle or when climbing hills will appear. This is usually caused by a weak coil or by a weak spark plug. So if you can determine which cylinder is missing , try swapping spark plugs. If the miss follows the spark plug, replace the plug. Or try swapping coils if it moves with the coil, try adjusting the coil or replacing the coil with one which has been tested to be good. Also some carburetors will run fine at idle but be either rich or lean at speed or under load, so you can also try the mixture adjustment.
Norm

[A Whiteman]

To short out a spark plug while the engine is running take a longish screw driver, place the end (tip) on the head or bolt and then lower the shaft to the spark plug head (where the lead is attached). That will ground the plug without 'shocking you'. As Norman explained, this can help you track down which cylinder is missing, then it makes it easier to start the analysis process (swap plugs, check coils etc).

I had a similar issue with my roadster - ran smoothly at idle and low speed but as the engine sped up it began missing badly, down to 2 cylinders firing at worst. Back to idle and it ran smoothly. After some head scratching I tracked the problem to the timer which was moving around at high speed and hence missing firing cylinders. It was an Anderson type and the flapper was knocking badly against a contact and skipping the next contact. Rather than figure out why I put in a Ford roller timer and have had no trouble since.

I mention this just to point out there could be other issues than just electrical or compression. You just need to start with the grounding test, then work through the possible causes.

[John kuehn]

I had a miss under a load when driving and after stopping and idling it would run smooth.

It turned to be a slightly loose plug wire to no.4 on the firewall to the coil box. This was on my 24 Coupe. After I tightened up the loose coil box wire no more skipping engine going under a load.

Those misses that show up and be so simple it doesn’t make sense sometimes!

If you have a miss check it at night in your garage and see if you can see any arcing or sparking. You might be surprised.

[Norman Kling]

It has been mentioned to short the spark plug to ground. One safety item I will bring up. Some vintage screwdrivers have a wood handle with the steel shaft running all the way through the handle. Either don't use that type screwdriver to short the plug, or be very careful not to touch the steel shaft.
Norm

[CatGuy]

I tried holding down on the points like in the picture. I couldn’t get any negative response from the car. I got a little buzz in my fingers. I tried the screwdriver to the spark plugs. No negative effects except one time when I shorted #3 the engine died. I switched #3 & #4 coils, but couldn’t get the same response. I’m thinking that I might not have a coil issue? I know the plugs are pretty fouled. I suppose that could cause the missing and skipping?

[A Whiteman]

Possibly, but I am little curious when you say you got no negative response from the car when earthing the points or the plugs with the screw driver trick. That is odd as a running car should immediately die a little when each cylinder is earthed out because it is suddenly running on 3 instead of 4 cylinders. The earthing trick is sometimes better done at a fast idle.

[CatGuy]

Possibly, but I am little curious when you say you got no negative response from the car when earthing the points or the plugs with the screw driver trick. That is odd as a running car should immediately die a little when each cylinder is earthed out because it is suddenly running on 3 instead of 4 cylinders. The earthing trick is sometimes better done at a fast idle.

It did the one time, but wouldn’t again. The RPMs seemed to decrease just a bit, but it kept running.

[Chris Barker]

The best way to find the bad cylinder is to take the top off the coil box, run at a slightly fast idle, then stop cyls 2 and 3 by stopping the points on the two centre coils with your fingers, then do the same but with 1 and 4 - the outer coils.
If all's well, you hear a 2-cylinder engine on each test. If a cylinder's gone, you only get one left.
Then all you have to do is find out which of 2 is bad.

[CatGuy]

The best way to find the bad cylinder is to take the top off the coil box, run at a slightly fast idle, then stop cyls 2 and 3 by stopping the points on the two centre coils with your fingers, then do the same but with 1 and 4 - the outer coils.
If all's well, you hear a 2-cylinder engine on each test. If a cylinder's gone, you only get one left.
Then all you have to do is find out which of 2 is bad.

I just stepped outside and gave that a try. No big difference at all. Does that mean my coils are good, then? Coming into work today I was able to top out at 25mph, but that's it. In low gear I got it up to 13mph and it wasn't going for anymore.

[Mark Nunn]

An E-Timer bypasses the coil points with fused jumpers. Shorting coil points will have no effect on engine performance, if I am correct. I don't know what timer you have but your results would be the same if you had an E-Timer.

[JTT3]

Scott (catguy) I suggest you not wind the engine up in low to 13 mph that’s not needed and not good on the engine overtime. Curious do you reduce throttle as you dump low for high? So based on what you said about the coils in response to grounding them. I wonder if the reason your not hearing or feeling a change in the engine is because certain coil/coils is/are not working at all. Do you have access to a coil tester? One that can actually tell you what the performance of the coil is? If no, then, (please no Cat Calls) while it’s not the best by any means but something that can help a little without great expense is to build one. It’s really easy for what it is & does. Basically the only thing it will tell you is if your coil will through a 1/4 spark consistently to another contact. You can make one with a meter or without just to find out if the coil will actually spark without the meter and with the meter the guesstimated strength of the spark. Very poor tool but it’s what a lot of old timers had and used for years. Best thing though is to send them off to be reworked by one of the members that rebuild them. I’ve use Mr Patterson but have used two others in a pinch. the difference in having them “tuned” LOL by yourself and having them done by someone that does it professionally often, is night & day performance. YOU WILL BE SENDING THEM OFF EVENTUALLY, if you are into your T long term. Might as well get a potential major issue out of the way early to concentrate on other T related things that you can do while waiting for them to be rebuilt. JMHO. Best

[Chris Barker]

One other thought; do you advance your timing after starting, and is it set so that it sparks just ATDC when the lever is 'up'?
And are you running it on magneto?
If running on 6v battery, you need a lot of advance.

[CatGuy]

Scott (catguy) I suggest you not wind the engine up in low to 13 mph that’s not needed and not good on the engine overtime. Curious do you reduce throttle as you dump low for high? So based on what you said about the coils in response to grounding them. I wonder if the reason your not hearing or feeling a change in the engine is because certain coil/coils is/are not working at all. Do you have access to a coil tester? One that can actually tell you what the performance of the coil is? If no, then, (please no Cat Calls) while it’s not the best by any means but something that can help a little without great expense is to build one. It’s really easy for what it is & does. Basically the only thing it will tell you is if your coil will through a 1/4 spark consistently to another contact. You can make one with a meter or without just to find out if the coil will actually spark without the meter and with the meter the guesstimated strength of the spark. Very poor tool but it’s what a lot of old timers had and used for years. Best thing though is to send them off to be reworked by one of the members that rebuild them. I’ve use Mr Patterson but have used two others in a pinch. the difference in having them “tuned” LOL by yourself and having them done by someone that does it professionally often, is night & day performance. YOU WILL BE SENDING THEM OFF EVENTUALLY, if you are into your T long term. Might as well get a potential major issue out of the way early to concentrate on other T related things that you can do while waiting for them to be rebuilt. JMHO. Best

I do close the throttle, but I really think it's idling way too fast. I noticed that I can drive it on level ground in low with the throttle closed or nearly closed. I tried slowing it down, but the screw is already way out. I think, from another post, the linkage going through the engine is backwards. Now, do I need to also retard the spark, too, while shifting? The car also shudders and shakes when shifting into high and then as I try to accelerate in high it acts like it's only a 1 cylinder and that's with the throttle lever ALL the way down!
I don't have a coil tester. I plan to do a compression test on it soon and maybe open up the timer and see what's going on in there.

[CatGuy]

One other thought; do you advance your timing after starting, and is it set so that it sparks just ATDC when the lever is 'up'?
And are you running it on magneto?
If running on 6v battery, you need a lot of advance.

Last year I bought a Model A as I had always wanted one so you could say I'm using that driving technique in regards to the spark control. I wonder if that also could be my issue? I do run the car on the magneto after starting. That doesn't appear to make a difference.

[JTT3]

Model A & T are a bit different with the spark/ advance. Steve Jelf on his website, https://dauntlessgeezer.com/DG52.html
has a diagram of advance & throttle I believe, you may find it of interest along with other tips for DIY info.

[A Whiteman]

The RPMs seemed to decrease just a bit, but it kept running.

That would be the effect you would find, the engine will slow but won't stop as the other three cylinders are still working. At a higher idle speed the engine would run a little rougher than when you aren't earthing out.
When you earth a cylinder and there is no change in rpm, then that is an indicator that is a 'crook' cylinder. Remove and clean plugs set gap to around 30thou and try again.

Remove coils check all contacts are clean and all wires firmly fixed (loose wires can be a big cause).

From your explanation it sounds to me like a timing issue, possibly fuel, but probably miss timed.

I am not familiar with your part of the country, but can you reach out to a local T club chapter of this club (or the MTFCI - the 'other' T club) as a visit from a long time T'er will quickly help pin down the issue (and will make new friends as well )

When changing up, I would do so at much lower speed than 13mph, that is a bit fast for the engine (low really is low). Back the throttle off and lift your foot smoothly and smartly (don't 'slip' it off). You shouldn't need to adjust the spark advance. When starting remember to retard the spark, then advance it again when running - rule of thumb is to advance as far as you can, (I know the diagram gives different positions for different driving conditions but actually, moving it to advance and leaving it there works just fine too. With experience you will find the 'sweet spot' for your engine (It seems each one is different), but I would not worry about finding it until you sort the other issues.

Juddering on the change up could be the clutch needs adjusting a little. There are a lot of 'could bes', most are 'easily' fixed, but figuring out which one is usually a bit of an issue, which is why we suggest looking for a local branch of either of the T clubs.

Cheers, don't be discouraged! it will be clear as you gain experience. And when it runs as it should that opens up a whole new time of enjoyment.

[Moxie26]

CatGuy. ...... Check the contacts inside the coil box, be sure they are shiny clean and are springing out so when the coil is placed in that position the electrical contact will be intact. Unfortunately a few years back I did replace those contacts inside the coil box with a new replacement offered by one of our vendors, and realized that it was not the same metal that Ford used. Those contacts lost their springing , and therefore the contact with the coil was interrupted at times and the engine ran very rough. Get yourself a rebuildable coil box with the original contacts inside, clean them up and use in your car. . ...... If those contacts lay flat inside the coil box, don't be afraid to pull them out to a point about a quarter to half inch