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Cub Won't Start...most likely cause???

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ILCubFan
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Cub Won't Start...most likely cause???

Postby ILCubFan » Sun Aug 09, 2015 2:13 pm

I last ran the Cub about a month ago and everything was fine when I parked it. Went out and tried to use it this morning and it won't start. In fact it's not firing at all. The battery is hot, plenty of fuel...so now I'm thinking it's probably electrical...possibly a distributor coil? What should I do next? It's a '48, I think, and has been converted to 12 volt. It usually doesn't hit on all cylinders until it's been running for 10 or 15 seconds, but I've never known it to not fire at all so this feels like something electrical has failed.

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ILCubFan
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Re: Cub Won't Start...most likely cause???

Postby ILCubFan » Sun Aug 09, 2015 2:58 pm

While waiting to hear from folks who actually know what they're doing I thought of a couple of more things. I have pulled a sparkplug wire off one of the plugs and I'm getting a nice hot spark against the exhaust manifold, so that would seem to rule out a bad coil or electrical issue, wouldn't it? I have tried removing the small plug above the carb and shooting in a little starter fluid and I'm still getting nothing. Seems like I've got everything I need, so why isn't it running?

staninlowerAL
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Re: Cub Won't Start...most likely cause???

Postby staninlowerAL » Sun Aug 09, 2015 3:09 pm

If you have a spark AT THE RIGHT TIME, fuel and air in the right mixture it should run or at least fire. Any chance the plug wires might have gotten switched? Next step is compression check, you might have one or more sticking valves especially since you said it would not run without missing for a short time beforehand.
Stan in LA (lower AL)
USAF & Reserves, Reg ARMY, ARMY NG (AL)

ILCubFan
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Re: Cub Won't Start...most likely cause???

Postby ILCubFan » Sun Aug 09, 2015 3:44 pm

My gut feeling is that if there's a sticking valve it's probably only one cylinder and it usually kicks in pretty soon after starting. Checking compression sounds like a great idea, but I don't have a compression tester. A quick on-line search turns up some testers under $30.00; would something like that be ok? That's pretty tight clearance in there under the hood, so is there a recommended type out there. What I'm seeing are ones with rubber hoses which would probably fit in there, but I can't tell if the ends are supposed to screw into the sparkplug threads. My wires are all in the right places, so even if there is a sticking valve in there somewhere shouldn't I still be getting some ignition? This thing is doing nothing!

Rodney51Cub
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Re: Cub Won't Start...most likely cause???

Postby Rodney51Cub » Sun Aug 09, 2015 4:17 pm

ILCubFan wrote: I have pulled a sparkplug wire off one of the plugs and I'm getting a nice hot spark against the exhaust manifold, so that would seem to rule out a bad coil or electrical issue, wouldn't it?


I also have a starting problem if mine sits for a while. The cap contacts corrode from all the high humidity in the area. Clean the contacts inside the cap just to be sure.

Rodney 8)
USAF 1976 - 1996

staninlowerAL
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Re: Cub Won't Start...most likely cause???

Postby staninlowerAL » Sun Aug 09, 2015 5:48 pm

No compression tester? You can remove the inspection cover for the valve tappets and watch for smooth or sticky operation and check the clearance. Cover removal and adjustment can be done without removing the manifold or TC lines. This won't tell you if the compression is low or no compression but if it has been a while since tuneup, probably needs to be done. Carbon buildup or something under one of the valves will also affect compression. If you have sticky valves, you can spray lube the top end through the spark plug hole and the lower end when the inspection cover is removed.
Stan in LA (lower AL)
USAF & Reserves, Reg ARMY, ARMY NG (AL)

ILCubFan
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Re: Cub Won't Start...most likely cause???

Postby ILCubFan » Sun Aug 09, 2015 6:31 pm

I'm happy to say that I finally got it running, but it was a raggedy A start. I pulled a couple of plugs and they were bone dry, which didn't seem right after several cranking attempts, so I poured gas in those two cylinders and tried again. It fired a couple of times! I had to keep it up with about 10 or 15 short hits on the starter, but could see I was getting somewhere and just kept it up until it caught. And I did notice that missing cylinder again, so I will follow up on valves. So, apparently it was fuel after all, which just goes to show you that sometimes what you think you know you really don't! Lesson learned! I guess I need to "prime" the cylinders with fuel if it sits for awhile. I appreciate all the helpful advice.

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mva1958
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Re: Cub Won't Start...most likely cause???

Postby mva1958 » Sun Aug 09, 2015 6:52 pm

Might be a good idea to check the points and the timing.
If only Mrs. Hoyt and Mrs. Clagwell had gotten along...

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Don McCombs
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Re: Cub Won't Start...most likely cause???

Postby Don McCombs » Sun Aug 09, 2015 7:23 pm

How old is the fuel in the tank? If more than 3 months, you may want to add some fresh fuel or drain and replace with fresh. Whatever you do, add some Seafoam to the fuel, according to the directions on the can, and run the Cub hard for an hour or so.
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Re: Cub Won't Start...most likely cause???

Postby Jim Becker » Sun Aug 09, 2015 9:08 pm

One sticking intake valve can keep the other cylinders from drawing in a fuel mixture. Good chance that is still your problem. You shouldn't have to dump fuel into spark plug holes to get it to start, no matter how long it has been sitting.

If one valve is sticking, you will often have little to no compression on one cylinder only. That can usually be heard as uneven cranking speed.

ILCubFan
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Re: Cub Won't Start...most likely cause???

Postby ILCubFan » Mon Aug 10, 2015 5:59 pm

I appreciate all the comments and suggestions. I don't hear anything different when cranking it over. The fuel is fresh. I typically don't let much gas sit in the tank over winter and I always add lead since it's my understanding that these older engines were designed to run on leaded fuel. So, why would I have a sticking valve? I agree, it shouldn't be this hard to start and I shouldn't be priming it...after all that's what the choke is for! So, if it is a valve issue can I remedy it with an oil additive...I'm thinking something like Lucas which my auto mechanic swears by? The engine runs well once it gets going and has plenty of power, so I'd like to think it's an easy fix!

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Re: Cub Won't Start...most likely cause???

Postby tmays » Mon Aug 10, 2015 6:26 pm

Read Don's advice again :-)
Thomas

ILCubFan
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Re: Cub Won't Start...most likely cause???

Postby ILCubFan » Mon Aug 10, 2015 8:39 pm

I just spent some time looking up what Seafoam is all about. If it can do all that it's certainly worth a try and it also meets one of my favorite criteria...easy! The consensus seems to be one or more sticking valves, so Seafoam it is. Thanks again and I'll let you know how it goes. One other thing that I've wondered about is spark plugs, not so much in regard to the hard starting issue, but in general. I've been using Champions, but was wondering if that is still a good choice.

staninlowerAL
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Tractors Owned: Cubs: (3)'49's, (1 is for parts), (1)'57 IH Cub LoBoy w/FH, (2)154 Number Series Loboys, (1 is for parts), '76 Longstripe w/FH, Mowers: C-22, Bush Hog 412, Pennington 59, Woods RM42CF, Woods 42, assorted FCub plows, planters, discs, etc. OTHERS: '49 AC B & Ind. Sickle mower, '61 AC D12 Ser 2, '52 8N, '56 Ferguson 35 Deluxe, '47 & '49 Avery V, '53 MM BG (offset), '51 JD M (regular), '56 JD 420C, with Blade and fire plow, '85 JD 850 (Yanmar) w/72" belly mower, '76? Yanmar 2TR15 1500 & Bush Hog SQ42S-2 mower, '78? FORD Dexta, '86 FORD LGT14D & 48" Mower, (2)Cub Cadets & Mowers (MTD), (4) Sears Surburban's, other MTD mowers, Jeeps & other misc. "treasures"
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Re: Cub Won't Start...most likely cause???

Postby staninlowerAL » Mon Aug 10, 2015 10:02 pm

IMHO, More importantly what is the right heat range for your use. Light duty/occasional use/limited run time = higher heat range in the case of Champion, D21 or your favorite brand equivalent heat range.
Stan in LA (lower AL)
USAF & Reserves, Reg ARMY, ARMY NG (AL)

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Trent M
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Re: Cub Won't Start...most likely cause???

Postby Trent M » Mon Aug 10, 2015 10:11 pm

Rodney51Cub wrote:
ILCubFan wrote: I have pulled a sparkplug wire off one of the plugs and I'm getting a nice hot spark against the exhaust manifold, so that would seem to rule out a bad coil or electrical issue, wouldn't it?


I also have a starting problem if mine sits for a while. The cap contacts corrode from all the high humidity in the area. Clean the contacts inside the cap just to be sure.

Rodney 8)


As another guy from Illinois (humid!) I will second Rodney's check. My 1974 had starting trouble last week. Usually, I'm pretty sure it will start if I just look at the key hard enough. I popped off the distributor cap and found the rotor contact covered in rust. 2 minutes with a piece of fine sandpaper and it starts right up now. This might not be your problem, but it is a good thing to keep in mind.

As a side note, I always start with the spark. Once the '49 wouldn't start so I took the distributor off and replaced the points, condensor, rotor, and cap then timed it just right. That's when I realized I hadn't turned on the fuel. Don't tell anyone.
Trent McPeak


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