Ford 8n no fuel on plugs

Byro01

New User
I am working on a ford 8n for someone. It's been converted to 12v, it's been sitting a couple of years in a barn. Whenever I got it I went to start and it fired right up. Ran for about 15 sec and died. Rebuilt the carb, replaced points and condenser. Cheked compression. Seems to be getting a good spark but will only try to start after sitting a couple of hours. After that nothing. Any ideas?? Plugs are dry. The fact that it tries to start after sitting overnight leads me to something in the ignition breaking down. Coil maybe? ?
 
Byro01,You say, Checked compression,well what is it on all 4 cylinders?
Seems to be getting a good spark? will it jump a 1/4" gap?
Does it build oil pressure while cranking over?
 
Front mount distributor or side mount?
When you checked the compression, what were your readings?

You have good blue/white spark at all of the plug wires?
If so, pull the drain plug out of the bottom of the carb, catch
the gas in a clear container to check for dirt/water and turn the
fuel valve on two full turns. It should run steady, not dribble
and you should get about a pint in two or three minutes.
Don't open the valve all the way, that gets into the reserve and
will pick up dirt off the bottom of the tank.
BTW, always turn the fuel off when its not in use.

If you don't get good fuel flow, there are three screens to clean.
On in the elbow going into the carb, one in the top of the sediment
bowl above the glass and one on top of that assembly inside the
tank. I'd leave that last one for last.

One last thought is to loosen the gas cap if you have poor flow.
They are gravity fed and the cap has to allow air in.
 
Oh yeah, you should not have fuel on the plugs.
If you do, its flooded.

I have never had a coil break down intermittently until it was hot.

What does it do with a shot of ether in the carb throat?
 
Byro01,Pull all 4 plugs and put a table spoon of ATF in each cylinder ,then replace the plugs.Crank it over a few times and let it set tonight.You said it war running a short time then quit.The valves could have stuck open.The ATF will free up the valves and also build compression on dry cylinders.
 
Front or side distributor?

" Coil maybe? ? "

Two chances: slim & none. It's not the coil.

" Plugs are dry. "

That's good. They're supposed to be dry. If they were wet, it wouldn't start because it would be flooded.

There are two schools of thought when it comes to getting a non-running tractor to start. One way is to just start replacing every part you can get to until it starts or you run out of money. The other way is to take a step-by-step approach to solving the problem, working from most likely to least likely. The trick to fixing these tractors (or trouble shooting any piece of equipment) is to be systematic about it. You need to isolate the problem step by step and work from most likely to least likely. At this point, after you " Rebuilt the carb, replaced points and condenser. Cheked compression. " you still do not know if you have a spark or fuel problem. That's the very first step in troubleshooting.

So it's time to start over.

It takes three things for an engine to run: spark at the right time, compression, & fuel/air in the right mixture. For the moment, forget about compression & concentrate on narrowing the problem down to spark or fuel.

There are three very important tools you always need to have in your N tool box: a 3 inch piece of wire w/ alligator clips on each end, a spark checker w/ an adjustable gap (* see below) and a 7/16 box end wrench. (see tip # 50 at the link below) And, you really do need a working ammeter on the tractor; it is a very important diagnostic tool. With these tools, you can quickly narrow down most N problems to spark or fuel.

Check for spark then fuel. First, turn the key on, crank the engine & look at the ammeter. What is the needle doing? Does it show a constant discharge, no movement at all, or does it move back & forth slightly? Next, hook up your spark checker, turn the key on & crank the engine. If the spark jumps the 1/4? gap, you probably don?t have a spark problem. If it won?t jump the ?? gap, you have a spark problem. If the ammeter needle shows a constant discharge, or doesn?t move at all, that also tells you that you have a spark problem. Jump the ignition switch w/ your jumper wire & see what happens. If it runs, you found the problem. If it doesn?t have spark after you jump the ignition switch, post back for more info on further troubleshooting. (and do not forget to turn the ignition switch off; see tip # 38

Next, check for fuel. Get a can & put it under the carb. Remove the bolt in the bottom of the carb; as long as the fuel is turned on, you should see gas flowing out of the carb. Let it run for at least 30 seconds. If it?s a dribble, or runs for 5 seconds & stops, or none at all, you have solved half the problem: it?s fuel related. If gas flows well out of the carb & only stops when you turn it off at the sediment bowl, chances are very good it?s not a fuel problem.If it does not have gas coming out of the carb at a steady stream w/ the bolt out for at least 30 seconds, you have a fuel problem. First, remove the gas cap. Your vent could be clogged & it vacuum locked. If that doesn?t work, tap the carb bowl w/ a hammer handle in case the float is sticking closed. (don?t whack it w/ the head of the hammer; you can crack the bowl). If you still don?t see gas flowing, the N has three fuel screens; one in the brass elbow, one in the top of the sediment bowl & one on the stem of the sediment bowl in the gas tank. Check the screen in the elbow & the screen in the top of the sediment bowl. (don?t worry about the one in the tank) Both probably need to be cleaned. If you have the fuel knob turned on all the way, & 1 gallon or less in the tank, it may be trying to feed off of the reserve inlet which is probably clogged. Only open it 2 full turns. Put at least 2 gallons in the tank. (and do not forget to turn the gas off; see tip # 9)

There are ways to check for spark & fuel that work & ways that don't. For example, having gas to the carb is nice, but having it past the float is what counts! That?s why removing the 7/16? bolt in the bottom of the carb is the way to check for fuel. And, same thing w/ spark at the plugs. Some folks think that checking for spark means pulling a plug wire off & looking for one. Well, it's the distance the spark jumps at the plug that gives you the info you want. It takes about 17kv to jump a 3/16" gap & 22kv to jump ?? in the open air. Remember, it?s 14psi outside of the engine & about 90psi at a 6:1 compression ratio in the cylinders & compressed air creates electrical resistance, so you really need the 17-22kv to fire the plugs when the engine is running. A store bought plug checker (in the picture) will work better than an old plug because it won?t shock the snot out of you like an old plug might!

Post back with results or more questions.



*If you don?t own a spark checker w/ an adjustable gap, buy one. In the meantime, an old spark plug w/ the gap opened to at least ?? will work. Ground it to a rust & paint free spot on the engine turn the key on & look for a spark.
75 Tips
 
good spark, and short starts and runs?

tells us time is good, points are good, and there is enough compression to start.

that leaves fuel...
 
Seems to have is not knowing for sure you have good spark. Check your spark and make sure it is a good blue/white and will jump a 1/4 inch gap or more at all the plug wires and if a side mount the center wire going to the cap.
When it dies jump off and recheck the spark and make sure it is still good.
If spark is good pull the carb drain plug and see if you have a good flow of gas. Catch it to check for water/dirt etc plus it should fill a pint jar in 3 minutes of less.
Had a tractor I was working on Sunday that had a carb full of gas but with the drain plug out of the carb the gas was not flowing and found the gas tank to be clogged up.
 
Ok, compression was about 105-110 across all cyl, getting 1/4" of spark, and great fuel flow out of bottom of carb. Removed carb again and every jet and passage is clean. I did figure out if I totally close all the air to the carb off with my hand it will start but dies as soon as I remove my hand. This leads me to think it's sucking air and not getting enough vacuum to pull the fuel up. Removed intake gasket was brittle but saw no signs of leaks. Intake checked good for cracks. Intake Gasket Possible Bad? Thanks for the help
 
" Removed intake gasket was brittle but saw no signs of leaks. Intake checked good for cracks."

That's not the usual way to check for a vacuum leak.

Get a hand propane torch and carefully spray it (unlit of course) around the intake manifold at the carb to manifold interface & the manifold to block gasket of the tractor while it is running. Or, you can use carb cleaner or WD40. If it speeds up, you found the leak. Sometimes (rarely) manifolds crack or get rust holes.

Lastly, when all else fails, you could have an air leak around the carb metering section. The likely suspects are leaky throttle shaft seals and/or a worn throttle shaft.

So, put it back together w/ a new gasket & plenty of copper coat & see what happens.
75 Tips
 
I couldn't do the tricks to check while running because it would only run with my hand over the carburetor. I will try the new gaskets and hope that was it. Any way to see if the carb is sucking air somewhere internally? Thanks
 
Not sure I agree with some of you. If you try to start a tractor and turn it over several times and it does not fire then why don't you have fuel on your plugs as the vacuum created with the motor turning over should pull the fuel into the chambers. Possible valve but unlikely all of them. If you have fuel then its probably an ignition problem. If you have no fuel on the plugs then I would day your not getting any. When it sets then some fuel is leaking into the carb therefore it starts and runs till bowl is dry. What I would do is hold your hand over the intake at the bowl and try to start it. That will tell you real quick if you getting gas. Doesn't take much to stop the flow of gas. If that's the problem it might actually solve your problem as it puts a lot more direct vacuum on your fuel system and may dislodge foreign material. Inline fuel filter just before the carb is a good thing to have as sediment bowls are okay but the filture will do a better job. Just my 3 cents worth. Norm
 
Got it figured out. Didn't realize the t screw on the bottom of the carb was actually an adjustment. Thought it was a drain. Once I realized this I couldn't believe I had did that. Anyways, runs like a top now. Thanks for the advice.
 
(quoted from post at 18:05:58 11/07/15) Got it figured out. Didn't realize the t screw on the bottom of the carb was actually an adjustment. Thought it was a drain. Once I realized this I couldn't believe I had did that. Anyways, runs like a top now. Thanks for the advice.

Glad to hear you got it running!
Have you figured out what carb it is?
It would be good to note that somewhere as the stock 8N M/S
carb didn't have a T screw on the bottom.

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