yet another misfire diagnosis

[Wayfarer]

car was running great one night, we took her to get some fast food. Next day we took her to get groceries, and she was all kinds of unhappy. Misfiring and down on power.
I had extra stuff here, so I swapped to a new set of spark plugs. No change.
swapped coils from Patterson (according to the previous owner) coils to Erik @ ModelTcoils.com ECCT set coils. no change
cleaned the (not in great shape inside) Ford roller timer. no change.
swapped to a new Anderson style timer. No change.

I live at 6000 feet altitude, so I expected my compression test numbers to be low, but... compression test shows #3 is about 7 psi less than the other three. If my Harbor Freight compression tester is to be believed, they were 35-35-28-35. These are estimates of course, the gauge has marks for 20-30-40... from 0 to 300. I need to get one that's like 0 to 100. thought about doing a leakdown just to back up the compression test #'s

at any rate, the misfire isn't steady enough in my opinion to indicate a cylinder issue.

during the last running session, I adjusted the mixture screw - I could barely move it - maybe 1/4 turn from center either direction, before the engine would begin to stutter badly and try to die. It didn't used to act like that. It used to be able to move within perhaps half a turn or more from center either direction before it would greatly affect the engine.

I'm now thinking I may have a carb problem

probably pull the carb tomorrow, replace the fuel filter, blow out the line, remove the bowl for inspection.

what do you guys think ?

[Norman Kling]

you might have a burnt or stuck valve, maybe improper valve lash in number 3. If a few drops of oil in number 3 bring the compression up, the rings might be at fault.
However, you mentioned that the fuel adjustment is different than before, I would suspect a carburetor problem. You also mentioned a fuel filter. The original filter was a screen located in the sediment bulb and usually doesn't cause a problem However, if you have a different type filter which was made for a newer car which had a fuel pump, that is very likely the cause of the problem. This would be especially noticeable if the car idles OK and runs at low throttle OK but when you give it the gas, it starts sputtering and might even quit running. I would recommend that if you have a different filter than the original type sediment bulb that you remove it and see if it runs better. Also there can be dirt in the float valve or the carburetor jets which would also cause problems.
Norm

[jiminbartow]

Does it do it both on Batt and Mag or just on Mag? Once, after going over a rough railroad crossing, while driving on mag, my T died. It would start on Batt but would die when switched to mag. I ended up having to drive home on Batt. When I got home, I discovered that when crossing the rough railroad crossing, the spring loaded magneto post point had popped off of the magneto coil contact button. I sharpened the Magneto post point, straightened it and carefully screwed the mag post into the hogshead so it dug into the solder button contact. Problem solved. Perhaps yours popped off, and is making intermittent contact. Jim Patrick.

PS. How is your gas and fuel screen? Has your ethanol gas deteriorated? Try removing the old gas, flushing the tank changing the fuel filter and putting in new gas (non-ethanol,if possible).

[Wayfarer]

I just put about 7 gallons of fresh ethanol free 87 octane two or three days before this episode started.

the car has an original sediment bulb and shutoff valve, a short rubber line with hose clamps, and then a translucent see through paper element filter. There is very clearly "stuff" in the bottom of the plastic filter.

the car acts up at all rpm.

the car behaves the same on mag or battery. Interestingly, and I would think unrelated, but the wire on the mag post came loose just a couple days before this episode, once I tightened the nut on the post it was fine.

[Steve Jelf]

I suspect the magic words here are paper filter. That by itself is often enough to give you fits. If it's clogged by dirt fine enough to get past the sediment bowl screen, even more so. As Norm says, try it without the filter.

[John iaccino]

I agree with Steve. Filters do not work well with gravity feed. Take it off.

[John kuehn]

Reading your initial post it sounds like it’s a fuel starvation issue. It doesn’t take much with gravity fed gas tanks. Is the gas tank cap vent hole stopped up? Good fuel flow to the carb?
Somewhere from the gas tank to carb is probably where the restriction is.
The add on fuel filter could be masking the problem.

[Wayfarer]

Thanks gentlemen !

Here’s a picture of the suspect at the moment
You can see how much stuff that filter has collected, that dark stripe in the bottom is all sediment.

I’ll patch in a hose to try it first, and then today is probably going to be the day to replace the copper line with steel

[Norman Kling]

I see that you put in some new gas just before this happened. On one tour a few years ago we stopped and filled our gas tank at a station along the way. Some other cars also got gas there and others got gas at another station across the road. After we got the gas, we sputtered along and had problems. We drained the sediment bowl and it ran better for a while. After we got good gas later on, the problem disappeared. There must have been some water in the station gas tank. The other cars which got gas at the same station also had problems. There might have been some sediment in the gas at the station and if the tanker had just filled their tank the sediment could have been stirred up and some got into your tank which clogged the filter. Modern cars usually have a float inside the tank and the gas is drawn into the car from the top of the tank. But in a Model T the gas from the bottom of the tank goes first into the fuel line. So if you drain some out of the sediment bulb, most of the bad stuff will be drained out. However if you have an inline filter, the bad stuff will go in and clog the filter.
Norm

[Wayfarer]

well...shoot...

drained the sediment bulb, removed the plug to clean the screen. There was more teflon tape in the sediment bulb than sediment. Someone used the teflon tape to install the side plug, rather than the lead gasket.
the screen didn't clean very well, so...I'm going to order the proper sediment drain valve (it has a plug right now), new screen, lead gasket.
Once I get those parts I'll run a new steel line with no modern filter, and I'll report back in a week or so.

thanks gang !

[Steve Jelf]

If the tank is infested by rust/dirt fine enough to get through the screen, you'll need to get rid of that too. BTDT.

[Wayfarer]

I promised to update this once progress was made.

I finally got her back together this morning -

I posted another thread last week about soldering the sediment bulb screen - Got that done, installed cap with new lead gasket - no leaks !
when I took the cap off, and removed the damaged and partially plugged screen I noticed that the hole through the plug was not drilled all the way through with a uniform diameter - so I ran a 1/4" drill bit all the way through before soldering the screen.

I knew the adapters used to attach the fuel line were incorrect, and a trip to Home Depot and then subsequent google search revealed that the compression nut is Model T specific, so I ordered that and waited. it showed up yesterday.

I decided to get it together and get it fired up to see if my ills were resolved, so I reused the existing copper fuel line, just removed the flashing from the tubing cutter use at each joint. (whoever installed it made the cuts and left the restricted openings) put a pice of rubber hose in place of the previously installed plastic / paper filter.

fired her up and went for a drive !
she ran GREAT ! It might be my imagination, but she seemed smoother and more powerful than before.

new ECCT set coils, new Anderson style timer, new spark plugs, and reworked sediment bulb definitely made a difference.

now -- to finish this job correctly I need to re-set the timer correctly (I had to pull it WAY down compared to before) , and install the steel fuel line.

[Scott_Conger]

Amazing what adding gasoline to an engine will do for running

There are no metal compression fittings on an original T fuel system...just than the squished felt or these days, neoprene sleeves. Either of these provide a drip-free connection with adequate strain relief to the pipe.

With gravity fed systems it is all about Cv (Flow Coefficient)

[tdump]

Paper fuel filters, Kohler had a issue with the Courage series engines, well several, but anyway,1 of them was a miss print in the owners and service manuals for the part number of the fuel filter.There are paper filters that will work on gravity feed but the micron rating is different,in other words, bigger stuff will go thru it. People would buy the filter the book called for and the engine would starve.They had printed the fuel pump filter number for the gravity feed system.

[Quickm007]

Thank you sharing this kind of issue. Very helpfull, I'm sure we will experience same issue in a near future.

I bought that fuel filter at Lang's, Do you think we could experienced same kind of issue too? Or this filter is better quality and made differently?

Fuel filter.JPG (25.99 KiB) Viewed 9473 times

[Scott_Conger]

the surest way to defy gravity, or at least fight it, is to use a filter

a cheap clear sediment bowl just before the carb will work without restriction and alert you to trouble brewing

[Tim Rogers]

I have never understood why folks insist on installing those needless and unsightly paper fuel filters. They are totally useless on an original fuel system. Perhaps it's a lack of understanding of what a sediment bulb is and how the fuel delivery system works on a stock T?

head.jpg (11.17 KiB) Viewed 9443 times

[Scott_Conger]

I believe that Mario has an early T which lacks the standard sediment bowl at the tank. What came with the car neither collects any real volume of material nor has a screen to filter out larger debris. It is really a glorified "elbow" with a drain. In this circumstance or any time a carb with an idle jet is installed, a glass sediment bowl just prior to the carb is helpful. I believe Stan Howe first posted this opinion and now that I've serviced a few of these carbs and just talked a friend with a '10 through this same sediment problem, I agree with Stan's original advice and have now adopted it for myself.

On later cars, an additional sediment bowl is pretty much overkill with a carb that is OE to the car unless it is a really pricey carb. Puddle carbs digest pretty much everything smaller than a dime.

[tdump]

I think alot of folks try to install a fuel filter because the gas tank may have some crud in it and the filter is much easier to swap out than to take a carb apart on the side of the road.
I had to look but I found where i got my info about micron size.
Here is a clip out of the artical.I Know I know,a 18 to 22 hp Kohler engine is not the same as a T engine but the princiable of gravity fuel flow is the same. what this says is 75 micron is workable for gravity feed



Craftsman made a typo in their documentation. The part number 25-050-22 (or 25-050-03) is a 50 micron filter designed for a fuel pump where they also make a 25-050-21 (or 25-050-07) which is a 75 micron filter designed for a gravity feed system like my engine is.

https://www.houzz.com/discussions/16203 ... lem-solved

[Wayfarer]

UPDATE TO THE UPDATE :
two short test drives, and then I drove her to work this evening. 6.7 miles one way.

in between the two test drives I reset the timer and re bent the rod. seems well.

the car most definitely has more power and drives better than before, but the misfire is still there. It's not noticeable while driving, but it is significant during idle. At startup / warmup, and at stoplights during driving.

the carburetor (Kingston L4) still has a very narrow needle adjustment range either lean or rich, so I'm wondering if I may yet have an internal carburetor issue, or possibly a vacuum leak.

I'll revisit compression test / leakdown to see if there's anything there.

might be time to pull the side cover to see what the valves / pushrods look like

[Scott_Conger]

very narrow richness adjustment on an L-4 is indicative of a damaged needle and seat on the jet.

Pulling the side plates to the valves will reveal oil, a little goop, leave you with another oil leak, and make you wonder why you just did that.

[Jerry VanOoteghem]

What kind of spark plugs are you using? Most modern plugs act just as you describe, especially in my '21 Roadster for some reason, and so I use only the original Champion X style plugs.

[Wayfarer]

very narrow richness adjustment on an L-4 is indicative of a damaged needle and seat on the jet.

Pulling the side plates to the valves will reveal oil, a little goop, leave you with another oil leak, and make you wonder why you just did that.

hahaha. thanks for the giggle and reality check Scott. ! (I was just thinking valve adjustment. This engine *might* have stainless valves and adjustable pushrods, as the other two done by the same original builder had)

thank you for the advice on the carb. I changed the needle some weeks ago. I took out the thumbscrew and put in one with two holes, so I could hook up the through-the-firewall adjustment. No problem appeared immediately, so it seemed like it worked fine. Might need to switch back to see if anything changes.

I'm going to use a propane torch to check for vacuum leaks today, and I'm considering drilling and tapping my intake for a pipe plug so I can attach a vacuum gauge,

[Wayfarer]

What kind of spark plugs are you using? Most modern plugs act just as you describe, especially in my '21 Roadster for some reason, and so I use only the original Champion X style plugs.

currently they are new Autolites. It had old Champions in it, and switching to the Autolites made no change

[Jerry VanOoteghem]

What kind of spark plugs are you using? Most modern plugs act just as you describe, especially in my '21 Roadster for some reason, and so I use only the original Champion X style plugs.

currently they are new Autolites. It had old Champions in it, and switching to the Autolites made no change

My T hates Autolites, but I know a lot of guys use them and like them. What gap are you using?

[Moxie26]

Wayfarer. ...... Is there excessive play between the throttle shaft and carb casting....any movement here combined with changing throttle lever, especially in take off in low pedal, will show as hesitation you describe.

[Wayfarer]

just tried the propane for vacuum leaks. No changes in idle or idle speed.
Curiously though, I put the propane directly in the throat of the carb, and nothing changed ? shouldn't the engine rpm have come up ?

unsatisfied with that, I used a spray can of mass airflow cleaner -- obvious rpm drops at the spray needle nut, throttle shaft, and rear intake port.

guess I know what I need to do next !

[Wayfarer]

What kind of spark plugs are you using? Most modern plugs act just as you describe, especially in my '21 Roadster for some reason, and so I use only the original Champion X style plugs.

currently they are new Autolites. It had old Champions in it, and switching to the Autolites made no change

My T hates Autolites, but I know a lot of guys use them and like them. What gap are you using?

.028"

[SteveTN]

I grew up running an International dozer my dad had (wish i still had it!).

The fuel tank was behind the seat and had this heavy cast iron cap with the following words embossed top and bottom:

BUY CLEAN FUEL

KEEP IT CLEAN


I cannot tell you how many times I have been reminded of that admonishment.

[Wayfarer]

bringing this one back to the top again.

I put the manifolds on, everything back together, and had the same rear intake port vacuum leak, and a massive exhaust leak at #1

Back apart again, clean everything up, check exhaust manifold for straightness -- all good.

I noticed at some point that that the exhaust pipe wasn't tight to the manifold, so when I took it apart I took the exhaust pipe out, and made sure to run the nut up and down the threads, make sure the flare would seat, etc.

I noticed that the recesses in the intake for the steel rings weren't concentric - nice and thick at the top, and basically non existent at the bottom. Inside the carb flange was also not very "clean", so I compared to another intake I had. The second one is much better - nice thick concentric recesses, nice clean inside the carb flange, so I decided to use that one instead.

once the next set of glands and rings showed up, I cut a pair of manifold clamps to try to do better installation. What a world of difference that made ! Installed with a bead of Ultra Black at each port, waited 24 hours.

today I put the carb back on with a vacuum port carb spacer I made, and then tried to put the exhaust back on. No dice. No wonder it was loose before, it hit the hog's head, and bound the nut badly.

cut, bent, welded the exhaust pipe. everything clears now, and it seals tight.

fired her up, checked for vacuum and exhaust leaks - all good except the carb. I have a Stromberg OF coming, so hopefully that takes care of the carb issues.

Still has a misfire - vacuum gauge shows a clear drop at the same time you can hear the misfire - it's erratic, so that leads me to sticky valve.

darn it !

posted short video of vacuum gauge on youtube https://www.youtube.com/watch?v=Z9apGeZ ... e=youtu.be

I'm willing to try some "mechanic in a bottle" type stuff, never been a fan, so I'm not hopeful. Almost time to open her up to see what's inside.

[Moxie26]

Mechanic in a bottle??... Good time to try Marvel Mystery Oil. I would put a pint in the engine oil and then add about 12 oz to a full tank of gas. Run it for a while and see if you notice any change.... I would dra in the hot oil and renew with a good quality oil of your choice plus a pint of Marvel mystery oil.

[Wayfarer]

bringing this one back to the top again

finally tore into the engine today, after the Seafoam treatments made no difference.

#3 exhaust valve stem shows evidence of "chatter" indicative of a sticky valve (could also be that the guide has been knurled, and the valve was stuck in place, leaving behind "witness marks"), and the face shows uneven discoloration - evidence of an eccentric valve or seat, and eventually a burned valve

EDIT 05/30 : cleaned up the valves. several show uneven wear indicating guide issues, and 3 valves have evidence of corrosion. the one pictured is by far the worst. Also - the guides aren't knurled

misfire case closed
on to a "valve job" thread