MTFCA Forum

Hi all,

Firstly a big thanks to Admin for the new forum, this is very cool. I've been away since our T went into storage in Sept '17 and due to a very busy year in '18 we only got her back out at Easter so we've got a bit of catching up to do...

So first thing I need to ask for help with is what looks on the surface to be a mixture problem - I don't seem to be able to lean it off enough to not foul the plugs. I've searched the internet for all the info available (most of it from this site), but even armed with that knowledge I'm still stymied.

Here's the problem. It has always ran rich, ever since we bought it. I didn't really think too much of the rich exhaust smell at first as the car is so old and my experience so low, but after 100 or so miles it was starting to misfire so it was obvious something was wrong. Pulled the plugs and they were (dry) sooty as heck. Cleaned them off and all was well again. We only did another 250 miles or so before she went into storage and I really can't remember if I needed to clean them again in that time. We've done only 43 miles since she came out of storage and already I've cleaned the plugs 3 times

I've adjusted the mixture control CW until it slowed down, then CCW until it started to falter and then found the sweet(est) spot somewhere between the two, but the plugs were fouled inside of 2 miles. I can't lean it off any more without causing it to run rough so I don't think it's a mixture issue, but something is causing the plugs to foul so quickly.

Even after 2 years of ownership the prolonged storage means I still only have just over 400 miles' experience so any help you guys could offer would be most welcome.

Reading your post, I’m suspicious of the “heat range “ of your plugs. What are you running for plugs?

Yes on what Les said...
Also, how are you cleaning the plugs ?
What year car and what carb are you running ?
Is the choke opening all the way ?
Fresh fuel in the tank ?
Timing/coils all set properly ?

Check the carburetor float.

Thanks for the replies fellas.

Plugs are Champion 25s.

Also, how are you cleaning the plugs ?
Wire brush and brake cleaner. They come up clean but dark, like the metal has been 'blacked'.

What year car and what carb are you running ?
1926 Touring, carb unknown (I'll take a pic and post in a sec)

Is the choke opening all the way ?
Er...don't know. I'm not pulling the choke to start it, it starts ok without that. Or did you mean something else?
EDIT: I just popped out and found that the choke is not returning all the way in when 'open', so this may well be the cause of the problem. I need to give it a gentle push to get it to go the last 1/8-1/4" home.

Fresh fuel in the tank ?
Yes, I suspected dull fuel so I drained and replaced with fresh 97 octane.

Timing/coils all set properly ?
Don't know. It doesn't have coils, it's been converted to points and distributor, but it seems to run very well until the plugs foul up so I kind of assumed everything was ok on that side of things.

Check carb float for what...and how? Might it be stuck somehow? Is the carb easy to disassemble and reassemble?

Thanks again, this is all very helpful.

Here's the carb:

A lot of people (?most?) don’t like Champion 25s. I remember Scott Conger advising to replace them. I like Motocraft F 11s.

I’m seriously considering upgrading to Champion X’s, but at £90 a set I’m still on the fence...

Thanks for the tip re the Motorcraft, I’ll see if I can find some.

I think the A-25 are dubious at best. On some of the earlier ones, the wire stud is loose in the ceramic. I’d also question maybe spark gap? Maybe check n post?

Motorcraft plugs work fine for me. To each their own on which plugs to use. Champion X are fine but your paying for originality and in my opinion and others they don’t run any better than Motorcraft or Autolite. Opinions will vary!!

I may be way off base here, but something said "intake leak" to me as I read your post. It seems counter-intuitive, but worth checking for - I think.

It's easy to check for. Simply start the engine, and spray either WD40 or carburetor cleaner around the two places where the intake manifold meets the block. If there is a leak, the material will be sucked in, and the engine will either race or stumble.

I have never had much success cleaning plugs with a wire brush. Sandblasting works best to get the carbon off the porcelain up inside.
Maybe time for a new set.

The float level can be checked "on car" by removing the bowl and the float should be about level when the fuel shuts off.
Also try leaning (CW) the mixture till the engine slows and back out only 1/4 turn.

Not had a chance to do any further checks, but I thought What The Hey and ordered a set of Champion Xs - at least I'll be able to rule that out and they'll look so much cooler

Ruxstel24 wrote: ↑

Tue Jun 04, 2019 5:37 pm

I have never had much success cleaning plugs with a wire brush. Sandblasting works best to get the carbon off the porcelain up inside.
Maybe time for a new set.

Interesting - why would you want to clean all the way up inside the plug, surely the only bits that matter are where the spark occurs, no?

Deke wrote: ↑

Wed Jun 05, 2019 12:39 pm

Ruxstel24 wrote: ↑

Tue Jun 04, 2019 5:37 pm

I have never had much success cleaning plugs with a wire brush. Sandblasting works best to get the carbon off the porcelain up inside.
Maybe time for a new set.

Interesting - why would you want to clean all the way up inside the plug, surely the only bits that matter are where the spark occurs, no?

With carbon build up, the spark can climb up the insulator and spark somewhere other than at the gap...

I had no idea, thanks.

Any commercial plug cleaner I have ever seen, is basically a sandblaster.
Another thing is after you blast one and break the glaze off the porcelain, they seem to get dirty/foul faster.
If your engine is right,(proper mixture, not burning oil, etc), you don't need to clean the plugs much, if at all.

The picture of your carburetor looks like a Kingston L4. There should be a spring right behind the choke lever on the side of the carburetor. That spring is to pull the choke open when you release the choke rod. It looks like someone has installed a coil spring from the choke lever to somewhere under the body. Be sure the spring holds the choke all the way open.

As stated above, once the spark plugs get carboned up, the voltage goes right to ground without jumping the gap.
Norm

I had a similar mixture problem with my 27, it had a Kingston L4 could never get it adjusted properly, changed it out to a Holley NH, runs good now.

I tried running Champion X's in my '15 and it absolutely rejected them! Seriously. Put in 25' s and ran fine. Back to X's just for kicks and ran awful. Back to the 25' s and thats what stayed in there until I sold the car.
I clean my plugs by soaking them in good old lacquer thinner! Its the elixer for model T's I swear! I'm afraid that too much sandblasting will wear away the electrodes and such. Just my thought is all.

Just a quick follow-up on this. I bit the bullet and bought a set of Champion X's and it appears to have done the trick. I've done about 50 miles or so since and the plugs look as good as new, so no more fouling up. Not sure how or why simply changing plugs should do it, but it seems to have so I'm happy.

Thanks all for your valuable help.

Almost any spark plug will ignite the fuel if the mixture is correct, however if the air fuel mixture is too rich even the best and most expensive spark plug won't ignite the fuel. If your plugs were fouling clearly indicates the fuel mixture was too rich. New plugs will only be a temporary fix and they will foul again. It is important to assure the float is at the correct level, the needle is not leaking and the choke is fully open. I have owned my 26 for 55 years and it has the original type plugs in it and they never have been changed and they have never fowled, I have however had needle valve issues from time to time that caused rough running and black smoke, but when corrected all was well again, I also had a cracked float that caused some unwanted behavior. I have never touched the spark plugs.

I used to own a '25 with a lot of miles on it, and I forget the brand of plugs that were in it, either Motorcraft or something else. I put a set of reproduction Champion X's in it, and the problem went away.