# 641 ford won't fire



## rogerru (Dec 22, 2016)

can't get fire to the plugs on my 641 ford tractor. i have good spark at the points. good visual spark and it pegs the volt meter when they break. power on both sides of the coil. all ignition items are new. no guarantee, i know. i bought the tractor not running so i can't say it worked before i installed the new parts. i thought about a hair line cap crack but didn't think that would keep it from trying to fire. it's probably something simple i'll be embarrassed to admit.


----------



## bbirder (Feb 26, 2006)

I'd change the cap and rotor before going any further.


----------



## FredM (Nov 18, 2015)

rogerru --- have a look at the carbon contact in the inside of the distributor cap, this is in the middle and contacts the rotor which distributes the spark to each spark plug, there also should be a metal contact on the rotor, some are fixed and some can be like a flat spring to make contact with the carbon contact.

also check the receptacle where the coil HT lead fits into the cap, this can get corroded at times and this will isolate the spark from going through to the carbon contact, for that matter check all of the HT lead connects in the cap too.

you can test the coil for HT voltage by removing the HT lead from the cap and hold about
1/4" from a good earth, turn the ignition on and use a flat bladed screw driver to make and break the points, if the points are open just bridge with the blade by bridging across the contacts and then move part of the blade away from one side of the contacts, if the points are closed, just open the contacts with the blade on one side of the contact.

I am not sure when you say " all items are new", the fact you mention the possibility of a hair line crack in the cap makes me feel the cap is old, I am sure you will let me know.


----------



## willys55 (Oct 13, 2016)

this may sound nutty, but I had a jubilee that was brought to me in a non running state that had new plugs, cap, points and rotor......after working on it for about an hour, I decided to start by starting over, I removed the cap and rotor and set them next to me on the floor when I noticed the rotor looked too short to reach the contact for the coil in the cap.....that's when I found out that ford had FOUR different distributor caps that varied in slight ways. Machine fired right up with the correct cap.


Just a suggestion for you


----------



## rogerru (Dec 22, 2016)

all new items are: plugs, points, cond, cap, rotor, plug wires, coil, coil to dist wire, items from that wire to points, dust cover. also i have good spark when the points break. i don't have the old items to compare to the new items, such as the rotor. but, i'll admit, the new items are not "genuine ford". i'm not close to a dealer. parts were purchased on line from various suppliers like yesterday tractors, ssb, reliable, etc. i think you're right about starting over. i'll have to get new "new" parts. still, everyone please continue to through suggestion at me.


----------



## Fallhunt42 (Apr 17, 2016)

Double check that timing is correct


----------



## rogerru (Dec 22, 2016)

will the timing keep it from just firing? at this point i need to know it will fire or try to start.


----------



## rogerru (Dec 22, 2016)

update. got new cap and rotor from a nearby auto parts store. i now have fire at the plugs but still the tractor won't fire. keep in mind, this is a project tractor.
now that i have good fire at the plugs, you'd think i just need to get fuel to the plugs and it would ignite. i have fuel thru the carb, put my hand over it to suck it in but no fire. the plugs are not wet. i then spray starting fluid in one plug hole and crank. no fire but it could have evaporated. so, i poured a little gas in a plug hole but still no fire. again, it's a project. i need to know it wants to start so i can move on to making it run. keep suggestions coming.


----------



## rhino (Jan 9, 2017)

Take compression of cylinders, you need at leased 90psi.:usa:


----------



## RC Wells (Dec 26, 2008)

Timing is critical, and when the distributor has been removed it is necessary to use the timing inspection port on the same side of the tractor as the distributor. There is a timing inspection port about an inch or so in diameter.

It is on the front of the bell housing cover, and should have a dust cover or plug inserted in the port. Once that cover is removed the front of the flywheel is visible.

Ford scribed timing marks on the flywheel that are used to locate degrees. 

Remove the spark plugs and the distributor cap, use an 8" long chunk of copper wire with an "L" bent at the top to keep it from falling into the spark plug hole in the event of dropping it.

Roll the engine over by hand until you get to 0 degrees on the flywheel and the piston is at the top of its stroke. You will either be at compression or off 180 degrees at the top of the exhaust stroke. If you are at compression TDC you can roll the engine over again with the wire removed and a finger over the plug hole and feel for compression as the timing mark appears again. If you finger is lifted a bit from compression when the timing mark is at 0, then you have TDC and it is time to set the distributor so it is properly aligned. Generally speaking this will be when the oil fitting on the distributor is pointing directly away from the engine block or slightly forward of that position, and the 0 is centered in the hole in the flywheel cover. The distributor rotor should be pointing nearly directly to toward the flywheel end of the engine when properly timed.

The distributor is now very close to where it needs to be, and the plug wires on the cap should be positioned so #1 is to the back toward the flywheel, #2 next to the block, and #3 and 4 according to the firing order. 

It should now fire right up and with a timing light you can fine adjust the timing before you tighten the distributor hold down. If you are experienced with timing a gasoline engine, you can also set the final timing by moving the distributor until the engine runs at its fastest idle, then backing it off just so the engine idle starts to slow.

It is real common for the distributor to be either 90 or 180 degrees out of time when they have been rebuilt and someone was not being as careful as they could have been with the timing or put the spark plug wires in the wrong location on the distributor cap.


----------



## rogerru (Dec 22, 2016)

i'll do the timing check per your directions. don't know if the distributor has been out but the plug wires were on wrong when i got it, so it is possible.


----------



## bbirder (Feb 26, 2006)

I think RC gave you good advice.


----------



## rogerru (Dec 22, 2016)

worked on it several times several hours this weekend. timing is approx 4 before tdc. compression is 120 on all cylinders. rechecked everything spark/fire related. has good spark everywhere. have the valve cover off to watch the valves (overkill since compression is good). i choke it till fuel runs out the carb but plugs don't seem to be wet. i've had each plug out, held against the head and shows good spark. just in case my timing check was flawed, i lifted dist and rotated 90 then 180 degrees. didn't help, put it back correct. it won't attempt to fire. i just need to get it to try, running right would come later. battery is charging now.


----------



## RC Wells (Dec 26, 2008)

Sounds as if you are making progress, if it is sparking on #1 and you can see the valves are closed when it is sparking, the timing is correct enough to fire with fuel.

S no fuel condition is pretty straightforward to correct.

I imagine you have already checked the fitting at the fuel tank to be sure the fuel is actually getting to the carburetor. These either have a brass fitting with cross hatch slots or a fitting with a screen that screws into the bottom of the tank. Old rust and sediment will clog that fitting over time.

I would now pull the carburetor and be absolutely certain that all the passages are open. The carburetors are very simple in design, so just get it on a bench with good light so you do not lose anything in the process, make notes if you do not have the repair manual, and disassemble and be absolutely certain each and every passage is open, and that the jets themselves are not clogged with gum and debris.

I recommend against using high pressure air to clear the passages, just use carburetor cleaner and a very fine wire such as a tip cleaner for a torch set. Work though each passage until all crud is removed, then if you feel a need for something to blow it out use canned pressurized brake cleaner. It is best not to be a smoker when cleaning a carburetor, or to have it near any source of flame.


----------



## rogerru (Dec 22, 2016)

i definitely have fuel to the carb. some time back, i put a kit in it. when i did that, soaked it over night in carb cleaner. i had the carb off as recently as yesterday. it was full of fuel. i'm more than willing to do it again and again. like you, i thought fuel was not getting to the plugs since fuel was running out of the carb but the plugs were not wet. that's also why i poured fuel in one plug hole but still no fire. i put my hand over the carb air intake and it has,what i believe to be, good suction. i'll re-examine the carb and use the canned carb cleaner and brake cleaner to blow it out. please keep suggestions coming.


----------



## bbirder (Feb 26, 2006)

You mentioned you changed the wires when you got the machine. Double check that they are in the proper firing order. They shouldn't have been out of place.


----------



## RC Wells (Dec 26, 2008)

What happens on these carburetors when running modern fuels is they actually completely clog the passages. Manually running fine wires through the passages is the only way to get them cleared. The carburetor cleaner works after the passages are open enough to flow air easily, the brake cleaner just blows out the crud.

In the future avoid gasoline with alcohol, or drain the carburetor when not using the tractor.


----------



## rogerru (Dec 22, 2016)

i'm going to disassemble the carb and clean it again. probably friday.


----------



## rogerru (Dec 22, 2016)

update: carb is 100% clean and clear. put it back on, no change, no fire. put my hand over the air intake of the carb, good suction. plugs are still not wet. remove 2 plugs and sprayed in the hole, still no fire. first time i've been this perplexed by an old ford. help please.


----------



## RC Wells (Dec 26, 2008)

Does your hand get wet from the rich fuel air mixture as you are cranking for an extended period with your hand over the carburetor intake?

If not, you still have a fuel problem. Perhaps no fuel getting into the float bowl?


----------



## FredM (Nov 18, 2015)

g'day rogerru --- the fact you have sprayed fuel into a couple of plug holes and not get a sign of life is strange, from all you have done with the ignition and now the carby is certainly strange.

you should be able to place a petrol soaked rag over the carby opening and crank the engine and you should get a result with the engine turning over and trying to start.

If you haven't done this yet, could you remove the tappet cover and remove #1 plug and bring #1 piston to TDC, check the rock of #1 inlet and exhaust valve and #4 inlet and exhaust, if #1 is in the rock position and #4 is in the valve closed position,(compression) rotate the engine 180° to bring #1 to the valve closed position (compression) and #4 in the rock position, doing this will show if the camshaft is timed correctly.

I know you have said you have good suction at the carby throat, but have you checked for any manifold or carby flange leaks ?.


----------



## rogerru (Dec 22, 2016)

yes. my hand serves as a choke and eventually fuel runs out. i've disassembled the carb several times and it's always full of fuel.


----------



## RC Wells (Dec 26, 2008)

Given you are correctly timed, have spark at the plugs, fuel in the air at the intake when choking, but still have dry plugs, I would check the barrier between the exhaust and intake manifolds for rust through.

Generally when that happens you will feel a puff of pressure on your hand as you are cranking the tractor with your hand over the carburetor inlet. It will have vacuum, then a puff that tries to blow your hand away. That puff is enough to keep the fuel laden air from reaching the intake valves.


----------



## bbirder (Feb 26, 2006)

Another point to check is to make sure the gear on the distributor shaft has not sheared or partially turned. Thi would throw out your timing.


----------



## rogerru (Dec 22, 2016)

yes, hand serves as a choke and gets wet after cranking awhile. also i've sprayed start fluid in the intake of the carb while cranking. no attempt to fire.


----------



## bbirder (Feb 26, 2006)

Do you know if anyone tore into that engine before you bought it? You might check the camshaft gear for timing. That might be why they sold it.
Never saw an engine that wouldn't at least cough or spit if it had fuel injected in the cylinder and spark introduced at the correct time. I still think your problem is in the timing.


----------



## rogerru (Dec 22, 2016)

this was an estate sale tractor. of course they said it ran until parked. by looking at it, i have a high percentage of confidence that it's never been down. per rcwells i'll assume i'll have to remove the manifold for that check. i'll also re-check timing.


----------



## bbirder (Feb 26, 2006)

Rogerru,
I meant the gear on the distributor shaft. Make sure the pin is not sheared. This could make your timing go all over the place.


----------



## rogerru (Dec 22, 2016)

eventho i see the rotor rotate when cranking, i lifted the dist and checked. all good. also rechecked the timing at the same time. it's got to be something simple that i'm missing and will feel stupid about later. haven't yet removed the manifold, as suggested. keep suggestions coming please.


----------



## rhino (Jan 9, 2017)

You could park a D10 Cat Dozer next to it, and tell it that if it wont start you will crush it. It might just scare it.:usa:


----------



## rogerru (Dec 22, 2016)

rhino. i've already threatened to disassemble and scatter the parts.


----------



## FredM (Nov 18, 2015)

you can't let this little old mean machine beat you, not long ago another bloke was having trouble with his Ford, a 140 series I think, he had been trying to get this to run for months and he was getting near to the end of his tether, we were posting everything we could think of and by chance he dropped that with a timing light connected the spark would stop and then start again, and this was concurrent, he had replaced the coil and all electrical as you have, in the end I browbeat him and said to fit the old coil back on and see what happens, his tractor run with the old coil and when he inspected his new coil, there was a crack in the HT column with some oil leak, I am not saying this is your trouble, I agree with you, it is something simple.

you have a couple of things to check, the plate between the inlet and exhaust manifold as RCWell suggested and the camshaft timing as I suggested, an engine will run with good compression, spark timing and fuel supply, you could remove the carby and hold a gas soaked rag at the inlet and the sucker should fire up when cranked, be it updraught, downdraught or side draft manifolds.

anyway, good luck with your trouble shooting, I hope you turn up something soon.


----------



## rogerru (Dec 22, 2016)

i'll try the soaked rag before i go to all the trouble of removing the manifold. also, i've ordered the hottest plugs i could find and another coil. i don't own a timing light but can get one. thanks.


----------



## rogerru (Dec 22, 2016)

also, will a timing light work correctly if the engine is only cranking, not running?


----------



## FredM (Nov 18, 2015)

The timing light is activated by the spark impulse through the clamp on #1 HT lead and should work while cranking.

The fuel soaked rag was only a statement of what should happen, you have used starter fluid with no result, you have checked the dissy timing a few times as being correct, the engine compression is ok, I wouldn't have ordered a new coil as you said the spark was good from the coil that you had fitted to the tractor, I don't know what the answer is to your starting problem, we are running out of options in trying to help you.


----------



## bbirder (Feb 26, 2006)

One more time!
Go back and read post 10 by RC. Then check the following from another tractor site

Okay this is really basic 99.99% of the time #1 cylinder is the front one nearest the radiator. You're dealing with a tractor that is 50 years old or so, a lot has happened in all those years and I bet the distributor being removed is one of them. Back in the day (when dinosaurs roamed the earth) Tractor and cars were a lot simpler and folks working on them took advantage of that. Remember this is a tractor, it was bought by someone so it could do things for them that helped them make money so they could eat and buy the kids shoes and there were no CORRECT POLICE. If it was stupid, but worked it wasn't stupid.

Consider the basic knowledge the distributor turns at 1/2 the speed of the crankshaft or for every two revolutions of the crankshaft the distributor goes around once. The technique for timing darn thing might of very well went something like turn the engine over until #1 cylinder is at top dead center (TDC) Compression, remember when the mark on the flywheel or crank pulley lines up #1 is at TDC of the compression OR exhaust stroke this is why you have to figure out because if you got the mark lined up you're right on or 180 degrees off. Once you establish TDC Compression you twist the distributor so the rotor is pointing at a distributor tower- that's now #1, then you figure our which way the distributor turns and attach wires with respect to rotation and firing order. Many distributors had a tang to drive them so if the engine internals are assembled right the distributor is right or 180 degrees off and some folks would just change the wire positions on the distributor rather than pulling the distributor and re installing it. 

STOP and think about it. Do not skip any steps or jump ahead out of sequence.
The firing order on this tractor is 1-2-4-3. NOT 1234

Do not switch distributor 180 and back. FOLLOW the instructions. It might run bad, but it should run if everything comes together at the right time.

One other question......Do you understand the difference between COMPRESSION and EXHAUST stroke? Not being sarcastic, just wanting to help.


----------



## rogerru (Dec 22, 2016)

no offence taken. remember i bought this tractor as not running. when i got, the plug wires where on wrong. they were 1 2 3 4. so, someone must have had a problem. probably why it was parked (long time) in the barn. as i installed new parts, i put them at 1 2 4 3. you mentioned compression vs exhaust stroke. when i have a puff on my finger covering #1 plug hole, i'm assuming that's compression. but even if it were out 180 or on the wrong stroke, wouldn't it at least burp? next time my son-in-law comes around, i'll get him to do the timing, he's a tech at a local car dealership. he can definitely see better than i. i'm still hoping it's a timing issue. i just don't understand the plugs not being wet if it's getting fuel but not burning it off. i'm of the belief it's something simple i've missed or doing wrong. when i (we) find it, i'll admit it here. please continue with suggestions.


----------



## bbirder (Feb 26, 2006)

Rogeru,

Is that tractor 6v or 12v? the 6 was positive grd and the conversion was 12v neg grd. Reading another post reminded me. If there is a resistor in the line try removing it. May give you better fire.


----------



## rogerru (Dec 22, 2016)

it has a 12v conversion. point me to the post. are we saying eliminate the resister and let the internal resister coil do the job?


----------



## bbirder (Feb 26, 2006)

rogerru said:


> it has a 12v conversion. point me to the post. are we saying eliminate the resister and let the internal resister coil do the job?


Read that on another site but can't find it again. It would be a quick fix and worth a try. He also had fire and fuel and couldn't get it to start. He removed the one that came with the conversion and it cranked right up. Who knows???

I saw another example that had fire and fuel but wouldn't start. He removed the new rotor and installed the old rotor. Even tho they were identical, his unit started right up. Carbon trace??? Shows fire but not strong enough to start.


----------



## rogerru (Dec 22, 2016)

i'm going to try it (i'm trying everything). maybe today.


----------



## rogerru (Dec 22, 2016)

update: It's Alive!!! and ran a bit. did several things so not sure which was the cure. i installed the hottest plugs, autolite 437. i re-traced the timing from scratch. that still looked correct. but i also bypassed the 12v conversion resistor and it burped. i'm leaning toward the resistor. it runs rough, burning out what i put in the cylinders. i reattached the resistor, it started several times on it's own and ran for very short periods because it currently has no radiator. i'll now start reassembly.


----------



## bbirder (Feb 26, 2006)

rogerru,

That's great news. I'd work around that resistor. From what I've read you may have the original resistor and also one that came with the conversion. Doubling weakens your voltage to the coil, and your fire is not as hot as it should be. It's my understanding that the conversion is only for the starting and charging circuits. The ignition is still running on 6v.


----------



## rogerru (Dec 22, 2016)

i belive you to be correct. if not for coil protection, why the resistor. thanks again.


----------



## RC Wells (Dec 26, 2008)

OEM coils use a resistor to lower the voltage to the coil so they do not overload the points in the distributor and cause arcing or burning during operation. 

Doubling the resistor will reduce voltage to the coil to between 3 and 4 volts, and that is usually not enough to energize the coil.


----------



## rogerru (Dec 22, 2016)

makes perfect sense. resistor probably was/is the most contributing item.


----------



## TraderMark (Nov 15, 2011)

How is the tractor running now rogerru?
Did you get it all straightened out?
I followed this thread every day, wishing I could help but I'm just not a gas man. All my work was on diesels.

Mark


----------



## rogerru (Dec 22, 2016)

it is now running and i'm in reassembly now. hope to drive it out of the garage this week. out of all the things i did to get it to run i believe bypassing the 12v conversion resistor was the determining factor. still an old ford tractor but one more that runs and will not go to scrap. that may not have been the outcome if not for the people on this forum.


----------

