Why won't it fire?

The Cub Club -- Questions and answers to all of your Cub related issues.
Forum rules
Notice: For sale and wanted posts are not allowed in this forum. Please use our free classifieds or one of our site sponsors for your tractor and parts needs.
User avatar
Glen
5+ Years
5+ Years
Posts: 5115
Joined: Mon Mar 19, 2012 7:33 pm
Zip Code: 00000
Tractors Owned: 1956 Farmall Cub with Fast Hitch, F-11 plow, Disc, Cultivator, Cub-22 mower
Circle of Safety: Y
Location: Wa.

Re: Why won't it fire?

Postby Glen » Sat Jul 04, 2020 4:00 pm

Hi,
Thanks for answering about it being a USA Cub.
The way they say on here to check the spark is to pull the center spark plug wire out of the magneto cap, and hold it by the insulation, with the end of the wire 1/4" away from a place with no paint, on the engine block, turn the ignition switch to on, and run the starter, there should be strong blue sparks.

It should also have blue sparks if you remove a spark plug, and connect it to the ignition wire, set the bottom of it on a bare place on the head, and run the starter.

Yellow sparks are weak, and the engine may not run.

If the spark is yellow, the ignition points, condenser, or coil could need replacing.
New ignition parts can be defective, and not work right, something in the magneto might need replacing again, if it's not making blue sparks.

Below is a pic of the magneto drive, governor gear. It should be in this position when the engine is at number 1 cylinder TDC.
Sometimes people have the governor off the engine, and turn the gear to the wrong position.
The timing gears have marks to align them to the right position.
The 2nd pic, from TM Tractor, shows the gear teeth, and the timing mark, on the left side of the pic. :)
Attachments
Cub gov gear.jpg
Cub gov gear 2.jpg

Moray
Posts: 11
Joined: Fri Jul 03, 2020 3:26 pm
Zip Code: 00000
Location: Scotland

Re: Why won't it fire?

Postby Moray » Sat Jul 04, 2020 4:09 pm

I spent some time on this again tonight.

Took the magneto off, removed the rotor arm cap and made sure the marks lined up.
Spun engine so no.1 was on compression/TDC. Made sure rotor arm pointed roughly upwards, and fitted magneto in to slots, with top of magneto fully in towards engine.
Rotated engine one revolution until crank pulley TDC mark lined up with pointer, then pulled the top of the magneto away from the engine, until the impulse tripped, and tightened nut.
Also checked the HT leads are where they should be.

I've not got a compression tester (I couldn't remember if I had one or not, as it's been a long time since I've used a petrol one!), but when turning the engine by hand, there is noticeable resistance as each cylinder is on it's compression stroke. I know I can borrow a tester from work, but I'm not sure if it'll be suitable for the bigger spark plug threads.

Tried tipping some fuel down the bores, and LPG, but still nothing.

I'm pretty confident nobody has been at the internal timing, as it doesn't look like any of the front cover nuts/bolts have been off for a long time. The magneto slots are at roughly 2 and 8, as per Rick Spivey's and Glen's posts, and the valves seem to be opening and closing when they should.

User avatar
Glen
5+ Years
5+ Years
Posts: 5115
Joined: Mon Mar 19, 2012 7:33 pm
Zip Code: 00000
Tractors Owned: 1956 Farmall Cub with Fast Hitch, F-11 plow, Disc, Cultivator, Cub-22 mower
Circle of Safety: Y
Location: Wa.

Re: Why won't it fire?

Postby Glen » Sat Jul 04, 2020 4:25 pm

Hi,
A problem the starters can have is the brushes and bushings wear out, then it won't work right.

The starter has a bushing at each end of it. If they wear, then the armature can rub inside the starter.
If the armature is rubbing, it makes the starter run slow, and use more power than normal.
It only takes a small amount of wear, the parts run close to each other.

If you remove the hood, the original Delco generator on a 1948 Cub has a cutout, or Relay, IH called it, on top of it. The model number on the plate on the 6 volt gen was probably 1101355.

Below is a page from the 1950 Cub operator's manual, showing the electrical system with the hood off.
It might help you identify if your Cub is original.
You can look up under the hood, using a light from the left side, and see if the gen looks the same as the pic, and has the Relay on top of it. :)

http://farmallcub.com/rudi_cub/www.clea ... e%2033.jpg
Last edited by Glen on Sun Jul 05, 2020 5:27 pm, edited 2 times in total.

Waif
5+ Years
5+ Years
Posts: 1017
Joined: Thu Aug 25, 2016 1:29 pm
Zip Code: 49343
Tractors Owned: 48 Farmall Cub "Seen Yore Dobbin"
53 F-Cub W/Loader.
Circle of Safety: Y
Location: Michigan

Re: Why won't it fire?

Postby Waif » Sat Jul 04, 2020 4:45 pm

Have you double checked spark plug gaps?

User avatar
Dale Finch
10+ Years
10+ Years
Posts: 5636
Joined: Tue Apr 27, 2010 11:34 am
Zip Code: 27517
Tractors Owned: '51 Cub "Bernie" with Fast Hitch
'55 Cub "Bruno" with Woods 59 mower
'55 Cub "Bertha" with Woods 42 mower
'55 Cub "Ben" with Woods 42 mower
'56 Cub "Boris" with Mott Flail mower
Circle of Safety: Y
Location: NC, Chapel Hill

Re: Why won't it fire?

Postby Dale Finch » Sat Jul 04, 2020 5:55 pm

As suggested above, did you disconnect the kill switch wire at the mag? I recently had a SA with a mag that wouldn't start. FINALLY (after rebuilding the mag!) disconnected the switch wire on the side of the mag, and it started right up! I replaced the wire from the pull switch on the panel to the mag, and no more problems.
Dale Finch
Image
Circle of Safety

User avatar
tmays
10+ Years
10+ Years
Posts: 3063
Joined: Wed May 11, 2011 8:59 pm
Zip Code: 39154
Tractors Owned: 1948 Allis Chalmers G
1947 Cub
1952 Cub
1940 Farmall H
154 Cub LoBoy
Location: Vicksburg, MS

Re: Why won't it fire?

Postby tmays » Sat Jul 04, 2020 6:24 pm

He says it fires, so kill wire is not the problem

Governor timed to the engine?
Thomas

User avatar
Dale Finch
10+ Years
10+ Years
Posts: 5636
Joined: Tue Apr 27, 2010 11:34 am
Zip Code: 27517
Tractors Owned: '51 Cub "Bernie" with Fast Hitch
'55 Cub "Bruno" with Woods 59 mower
'55 Cub "Bertha" with Woods 42 mower
'55 Cub "Ben" with Woods 42 mower
'56 Cub "Boris" with Mott Flail mower
Circle of Safety: Y
Location: NC, Chapel Hill

Re: Why won't it fire?

Postby Dale Finch » Sat Jul 04, 2020 6:54 pm

Ah Yes!! DUH! :oops:
Dale Finch
Image
Circle of Safety

Gary Dotson
Team Cub Mentor
Team Cub Mentor
Posts: 4612
Joined: Thu Aug 03, 2006 6:20 am
Zip Code: 43358
Tractors Owned: 48 Cub Diesel (Cubota)
53 Cockshutt 20 restored (Shooter)
52 Cockshutt 20 unrestored
47 Leader "B" (Herckie)
49 Leader "D" (Princess)
49 Leader "D" very rough
48 Leader "D" unrestored
Kubota B6200E
Kubota B6200HST
Kubota B8200HST-D
Circle of Safety: Y
Location: OH West Mansfield

Re: Why won't it fire?

Postby Gary Dotson » Sun Jul 05, 2020 7:44 am

Sometimes they can be just plain cantankerous. You might have to pull start that first time. I was once visiting George Willer and he had a Cub that he had just assembled and was ready to fire up. We cranked on that thing till we turned blue, checked and re-checked everything, still wouldn't fire a beat. George had a very large electric drill and he had made an adapter to fit the crank opening. We started spinning it with that thing and after a lot of spinning, it finally fired off. After that, it was one of the best starting Cubs George had. It made no sense at all!

User avatar
tmays
10+ Years
10+ Years
Posts: 3063
Joined: Wed May 11, 2011 8:59 pm
Zip Code: 39154
Tractors Owned: 1948 Allis Chalmers G
1947 Cub
1952 Cub
1940 Farmall H
154 Cub LoBoy
Location: Vicksburg, MS

Re: Why won't it fire?

Postby tmays » Sun Jul 05, 2020 7:52 am

Agree with Gary. When they won’t start up and I feel everything is right, we pull it to start
Thomas

ntrenn
5+ Years
5+ Years
Posts: 773
Joined: Tue Apr 17, 2012 7:55 pm
Zip Code: 47119
Skype Name: ntrenn
Tractors Owned: 63 Cub 221833 in family since '69
65 Lo-boy 19648 with an un-stuck #4 - it lives!!!
144 Cultivators with disc hillers
193 Plow
42C mower
59L mower mounted on the Fcub
23A Disc - lost possession
Circle of Safety: Y
Location: Indiana

Re: Why won't it fire?

Postby ntrenn » Sun Jul 05, 2020 9:54 am

Gas fouled plugs? Have had that problem a couple of times....didn’t believe it until I had it happen to me. Will cost about $10 to put in new plugs.

Moray
Posts: 11
Joined: Fri Jul 03, 2020 3:26 pm
Zip Code: 00000
Location: Scotland

Re: Why won't it fire?

Postby Moray » Sun Jul 05, 2020 3:48 pm

I've not had any time today to try anything, but it's got a new set of plugs in it.

Attempting to pull start it was something I thought about, but I wasn't sure how well it would pull start.
If it's dry tomorrow, I might get a towrope out and get somebody to give me a tow around the field, and see if we can eek it into life that way.

Eugene
Team Cub Mentor
Team Cub Mentor
Posts: 19339
Joined: Fri Jul 02, 2004 9:52 pm
Zip Code: 65051
Circle of Safety: Y
Location: Mo. Linn

Re: Why won't it fire?

Postby Eugene » Sun Jul 05, 2020 3:52 pm

Tow the tractor from the drawbar and not the bolster.
I have an excuse. CRS.

k hutchins
5+ Years
5+ Years
Posts: 606
Joined: Tue Mar 27, 2012 5:48 pm
Zip Code: 48843
Tractors Owned: 1948 Farmall Cub
193 plow
1948 snow/grading blade
Woods 59 C3
Cub 144 cultivator
Cub 22 mower
Cub 172 one row planter
Original manuals for all the above
Circle of Safety: Y

Re: Why won't it fire?

Postby k hutchins » Sun Jul 05, 2020 8:56 pm

Eugene
Having never done it, please clarify. You tow it backwards then using the draw bar? Or reverse the draw bar and run your rope/strap under from the front? I'm confused.
Why is there never enough time to do the job right, but always enough time to do it over. :?:

Bob McCarty
Team Cub
Team Cub
Posts: 10887
Joined: Tue May 25, 2004 8:02 pm
Zip Code: 80501
Tractors Owned: Cubs, MH Pony, Shaw, Allis G, 1934 Silver King, JD LA and LI, Gibson D, David Bradley Tri-Trac
Circle of Safety: Y
Location: CO, Longmont

Re: Why won't it fire?

Postby Bob McCarty » Sun Jul 05, 2020 9:08 pm

Run a chain or tow rope from the draw bar forward, under the front axle to the pulling vehicle. Have the Cub in 3rd gear, gas and switch on, and let the clutch out after a little speed has been picked up.
"We don't need to think more,
we need to think differently."
-Albert Einstein

User avatar
Dale Finch
10+ Years
10+ Years
Posts: 5636
Joined: Tue Apr 27, 2010 11:34 am
Zip Code: 27517
Tractors Owned: '51 Cub "Bernie" with Fast Hitch
'55 Cub "Bruno" with Woods 59 mower
'55 Cub "Bertha" with Woods 42 mower
'55 Cub "Ben" with Woods 42 mower
'56 Cub "Boris" with Mott Flail mower
Circle of Safety: Y
Location: NC, Chapel Hill

Re: Why won't it fire?

Postby Dale Finch » Sun Jul 05, 2020 9:27 pm

Just to add to Bob's post, you don't need to turn the drawbar around.
Dale Finch
Image
Circle of Safety


  • Similar Topics
    Replies
    Views
    Last post

Return to “Farmall Cub”

Who is online

Users browsing this forum: 1Sarge, Glen and 2 guests