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Model T Ford Forum: Forum 2017: Starting
Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom D on Thursday, August 10, 2017 - 10:43 am:

A general question I have wondered about, maybe someone here may have some insight. My 1925 touring typical starts easily. When warm typically with less than 1 revolution, and although I do not use it often, has started with 1/4 turn with the crank. Anyone know why these old engines can start with so little cranking, when modern engines, although they are extremely reliable, often seem to crank several revolutions to start?


Top of pagePrevious messageNext messageBottom of page Link to this message  By dale w on Thursday, August 10, 2017 - 11:11 am:

A model T just needs a decent whiff of fuel, some compression and a spark to go.

A modern gasoline engine car needs compare the resistance factor in your key or fob to the one in its security code, then wait to get a signal from a crank sensor for the ECM to process and relay to the ignition system along with an OK from the oil pressure and fuel rail sensors which may take a second or two before everything is up to pressure and ready to go.


Top of pagePrevious messageNext messageBottom of page Link to this message  By G.R.Cheshire on Thursday, August 10, 2017 - 11:20 am:

I think Dale has it right but to put it more succinctly....The computer can't think that fast!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Thursday, August 10, 2017 - 11:37 am:

Wait until it starts with no turn of the crank!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erik Johnson on Thursday, August 10, 2017 - 11:54 am:

A well executed hand-crank start on battery is essentially a free start.

Watch this video - Royce Peterson's father cranking a T - he was 91 years old at that time. Notice that he slowly lifts the crank. He is merely putting the a piston in the proper position and letting internal combustion take over.

https://www.youtube.com/watch?v=RhEnNzv6LBM

My 2003 Pontiac Grand Prix starts very quickly including cold engine starts in below zero weather. However, I always put the key in the "on" position, listen a couple seconds for the fuel pump to shut off so I know the fuel rail is pressurized and then put the key in start position. It starts so fast I only need to put the key in the start position momentarily.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Curt Brainard on Thursday, August 10, 2017 - 12:12 pm:

It is because the coils provide multiple sparks over many degrees of rotation vs a single spark with conventional ignition.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dufault on Thursday, August 10, 2017 - 01:19 pm:

Not sure that I buy that theory, Curt. With my engine, one healthy spark when the fuel/air mixture is just right, and the piston is in position to go down, the flammable mixture explodes and starts the crankshaft rotating quite well.

Just one good spark at the proper time gets my engine going...No need for me to manually rotate the crank.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Thursday, August 10, 2017 - 03:11 pm:

I've often heard people say the first spark is the one that does it, but on the other hand, take an aircraft engine running on two mags, cut one mag off and there is a notable decrease in RPM. That other spark is doing SOMETHING.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dufault on Thursday, August 10, 2017 - 04:15 pm:

firing the other plug??? (2 plugs per hole, no?)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Thursday, August 10, 2017 - 04:55 pm:

Yes, 2 plugs per cylinder on the airplane engine, but only one spark per plug. But in normal operation, there are two sparks (one from each plug) per power stroke. I'm not an A&P, so I can't say for sure, but I assume they are supposed to be simultaneous, but as they are driven mechanically, I doubt they both fire EXACTLY at the same time.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom D on Friday, August 11, 2017 - 08:51 am:

Thanks for the thoughts, but I am still not sure I can pin it down. I did not necessarily mean computer controlled engines. It seems the typical lawn mover, grass trimmer, 1960-1980 car, etc., all need more than a 1/4 crank to start.


Top of pagePrevious messageNext messageBottom of page Link to this message  By dale w on Friday, August 11, 2017 - 10:53 am:

Any grass trimmer or small engine without a storage battery and many of the earlier lawn mowers use a flywheel magneto to energize the coil, just like a model "T" with the switch on "MAG".

Like a "T" on "MAG", you have to spin it fast enough to generate enough field current to excite the coil(s).

I have several old Ford tractors (Fordsons to 801 series) and some will start with the tap of the key while others will take considerable cranking.
Sometimes (when I'm at home without witnesses) I can get a free start off of a Fordson, and the next time I will have to crank it for several minutes (when I am at a well-attended tractor show). It uses the same system as a Model "T", with an added 6V lantern battery hidden in the tool box to start it like a "T" on "BAT".

My "N" series tractors all use the same conventional points type ignition and some fire right up and others don't. Changing distributors and carburettors sometimes helps, sometimes it doesn't.
There are alot of variables- individual engine wear, oil viscosity, fuel quality to take into account I guess.

The Model "T" ignition, primitive as it is, has an big advantage at start up and slow cranking speeds with its bank of trembler coils and a storage battery to supply full voltage to its coils instantaneously and over a longer period.


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