1913 engine on our touring. Irregular miss fire worst on Mag, little on Bat. Seems to run a little better once engine at normal operating temp.
New babbit, line bored, new pistons,rings,valves re seated, new mag coil,coils set up by professional on HCCT. magnets recharged by laying a mag ring on flywheel.
Running on mag, 8 volts at idle, 26 volts rev'd up.
Compression is good and equal.
Changed each spark plug
Changed each coil
Cleaned coil box contacts and bent them out a bit to ensure good contact with coils.
Checked mag post for clean contact.
Replaced timer.
Can't isolate the miss to one cylinder.
Cleaned out carb, although it was clean.
Took coil box apart, all wire connections good, switch OK.
What am I missing???
Thanx in advance
Wilf
Spray a little oil around the intake manifold to carb gasket and around the intake manifold to engine block gaskets to check for an air leak. If you notice a change in how the engine runs you found the leak.
Stephen
If there really is a change from BAT to MAG then it points to ignition as the source however timing might be the only thing that makes it seem like BAT and MAG are different. Place the car in total darkness if possible and start up the engine with hood off the car. Look for any high voltage leaking anyplace as a visible spark. Check all around the coil box. You may or may not be able to see arcing within the coil box. If you are running an all wood coil box I would suspect your coil box might have some carbon tracks in it since you have ruled out everything else. The later 13 had metal box with wood back and that wood back might also be carbon tracked. Those are very hard to find. If you can borrow a coil box from another car, swap it and see if that fixes it since then you will at least know the cause.
You say "changed coils" Did you change all 4 coils, and if so, did the coils run well on magneto in another car? This problem sounds as described as a coil problem. Other possibility could be the switch. Maybe making good contact on battery, but not so good on magneto. Some problems are very hard to trace. I have had a timer problem which I thought was in the coil box or coils, but found out that it was in the timer. The difference between running on battery or magneto, is that the magneto timing is determined by the location of the magnets to the magneto coils inside the engine. When running on battery, the timing is completely determined by the position of the timing rod. Therefore, if one or more segments of the timer are worn and not making good contact, the spark on that cylinder might be a little late, and not as noticeable a miss, but when running on magneto, the actual impulse might come right at the bad point in the timer. This might change to some extent by slightly adjusting the spark lever either advance or retard so that the impulse will come at a good point in the timer. A new timer could fix the problem if that is what is causing it.
Norm
Hey Guys
Thanx for these suggestions.
I do have another coil box, which I'll try in a couple of weeks.
Gone sailing for 10 days
Cheers
Wilf
With all you have done the intake leak theory sounds likely.
Sounds like carbon tracks to me also
Possible worn camshaft.
I'm with carbon tracks too. Provided the coils are HCCT'd.
Took the coil box out of the 14 and tried it, no change.
Yes the worn cam might be next, but I'll try a re seat of the intake manifold and see if that makes any difference.
I do note that it does run a lot smoother on Batt, than Mag, so I'm steering my thoughts toward the Mag.
Is there a difference in engine speed when the lever is pulled back as opposed to when it is in the forward position? Before I rebuilt my '27 the mag worked but there was a noticeable difference in the way the motor ran when the end play was reduced. It ran better on battery but since it still has a 6 volt system it still was not great.
The 14 roadster from which I swapped the coil box runs perfectly. When I put it in the 13, it still ran rough on Mag, no change. I pulled the manifolds this AM and re seated the intake with some sealant, no change. I checked the voltage of the mag when running on mag again, and I see 8V at low idle, and 25V at a fairly high rev. Still misses!
Still runs smoother on Bat.
Coils where checked on a HCCT.
Constant adjustment of mixture to get smooth running doesn't stop the misses.
Took carb apart to clean with lacquer thinners, but it was clean.
I guess things are starting to point to the Mag ring, but it is new and would mean pulling the engine again.
Before you take the engine apart or the mag ring, have you checked the compression on the engine? With all the spark plugs out and the throttle and choke open, check the compression one cylinder at a time. Turn over the engine about 10 turns for each cylinder and record the reading starting from #1, the front cylinder. All 4 should be somewhere around 50 ft lbs and all 4 should be nearly the same compression. The compression will vary somewhat, being highest at sea level and dropping with altitude. If you have good compression, you don't need to repair the engine. You say the voltage is up to 25 volts AC on the mag, so it should be enough to run smoothly on mag. You also say it runs smoother on battery.
What have you done to the coil box other than clean the contacts? Did you replace the wood? There is a high chance that you have carbon tracks in the wood, which will allow some of the electricity to bypass the coils.
If you haven't replaced the wood on the coil box, that is the next thing you should do. You can get a kit with a plastic material which looks like wood, but will not draw water or burn carbon tracks. The vendors have it, or they also have new wood, if that's the way you want to go. If your car has been parked outside in the rain, it is quite possible the wood got wet at some time in the past. Wet wood will draw the spark to ground and once that begins to happen, will burn a carbon path into the wood.
Anyway, it costs much less to replace the wood, and that would be the next step I would take before pulling the engine to replace the mag ring.
Norm
Val also suggested something that could be leading to your problem. He said does it run better with the lever back or forward? That got me to thinking of crankshaft endplay. You can check for endplay by going to the front of the car and trying to pull the crankshaft pulley forward, You could use a big screwdriver as a lever. Don't pry too hard so as to bend anything, but see if it will noticeably move forward, then pull the parking brake lever back and the flywheel should move backward. I had a T which moved about 3/16 inch forward and backward. That movement can be fixed by building up the thrust surface on the 3rd main cap or replacing the cap. The mag will not work correctly if the gap increases moving the magnets backward from the coil ring. The short term fix is a distributor, or other aftermarket device to run on battery. The long term cure is reducing the endplay and correctly gapping the flywheel from the ring. To do the long term cure, it will be necessary to pull the engine, and while it is out, check all the bearings and repour if needed, also replace the ring whether the existing one is good or not, and recharge the batteries. This fix will last a long time, but while it's out, it's a good thing to fix everything. That even includes checking the transmission and 4th main and replacing everything that's worn. If you want to use the car this summer for tours, perhaps, the short term fix will get you by, and then next winter do the long term fix.
Good luck,
Norm
Thanks Norm
When I tried the coil box from the other car, it made no difference. Just checked for crank end play, and as far a I can tell, there might be 1/16" but not much more. Would not the crank end play be restricted if the hand brake was on with the engine running?
This engine had a rebuild last year, new babbit line bore pistons and rebore. I did not replace or touch the cam, but it appeared OK.
I haven't tried a compression test, but they feel quite even when cranking.
Wilf-
Maybe you have a break in your wiring somewhere that is causing the intermittent miss? Check the continuity of your wires or maybe swap out some different wiring.
: ^ )
Keith
Still sounds like an intake leak or perhaps a blown head gasket or a stuck valve. 8 / 24 Volts measured tells me you don't have a problem with the magneto or crankshaft end play. You swapped in the coils and carb from a good running car, right?
I would do the compression check next just because it is so simple and easy. Then if no obvious problems from that swap the intake manifold for a different one. The 1912 - '13 aluminum intakes are notorious for cracking or becoming deformed, which leads to a leak. This is why Ford went to the cast iron intakes which seal so much better.
1/16=62 thousandths, if my math is correct. That would mean the gap would vary as you run the engine. Normally the greater gap would be when you are idling in neutral, in reverse or in low. When you drive it, does it seem to miss more in low than in high? The gap would also increase when you go uphill but decrease when you go downhill. I think you have found your problem.
Norm
You say the coils were checked on a hcct, but were the capacitors replaced in the coils? I had a miss at higher speeds when running on mag, but not on battery. I had 2 coils that I had rebuilt and 2 with old capacitors. Swapped out each coil 1 at a time and still had the miss, finally replaced both old coils with rebuilts(new caps installed) and the miss was gone. My best guess was the capacitors were acting up with the higher voltage from the mag, but still able to handle 6v battery voltage. Jim
I have since rebuilt the 2 coils that gave problems and they have worked fine for over a year now.
Royce
Yes the coil box I used to replace the original is from a sweet running 14 Roadster.
Yes I will do a compression check and see what numbers I come up with.
The coils where all rebuilt by A coil rebuilder, and the substitute coils all work fine in the other car
Jim your thoughts are interesting!
Thanks for all the help guys,
Regards Wilf
Wilf:
You said you checked the Magneto voltage at 8/24 while running on Magneto. That is not really the way to check it. You check the magneto while running the car on BAT and using a known load on the magneto such as an 1156 bulb. But just so I can follow up on your previous test - did you use an analog meter (with a needle and scale) or a digital volt meter? Testing the magneto properly is a key ingredient to this hunt.