Wisconsin v-4 won't start

uglydukwling

New User
I just installed a used VH4d in a manlift. Before I got it, it had been sitting for years, but it started easily, ran smoothly, didn't smoke, seemed to have all the power it needed. I used it for about half an hour, then shut it down.

A month later, it wouldn't start. It fires, but won't catch. There aren't many things that could go wrong just parked. (e.g. if the timing was right before, it can't be wrong now) It has spark (it's a magneto ignition version). The float bowl fills with fuel. There's no fuel dripping from the carburetor. The plugs were a little sooty, but not wet. (I cleaned them anyway) They are in new condition. The obvious answer is that a speck of dirt got into the carb, but I dismantled it and it's immaculate inside. All passages are clear. It fires on starting fluid, but no better than on gasoline.

What is there left to try?
 
Could the sparkplug wires somehow have gotten "scrambled" at the mag? Also, is there a "kill" wire attached to the mag? If so, disconnect it for testing.

I don't know if you have a manual, so I've attached a link to FREE downloadable factory manuals below, you will need one for the next step.

Check the timing and compression.

If those check out, it mite be worth trying a new set of sparkplugs.

Sometimes, even plugs that look "good" can have deposits on the insulators that prevent good sparking.
Link to manuals
 
For some reason. B0b's reply doesn't appear in this thread, but I found it in "Topic Review".

I have the manual. One thing it mentioned was that when these engines are out of use for a long period, it's normal for them to lose compression. I didn't consider a month to be a long period, since the old engine regularly sat for several months every winter, and this engine had been sitting, probably for years, before I bought it. I tried putting oil in the cylinders as the manual suggested, anyway. It burned the oil (lots of smoke) and the compression came up from 60 lb to 100, but it still wouldn't run.

Even though there appeared to be nothing wrong with the carb, I replaced it with the carb off the old engine, since I knew it worked. No difference.

If it had been parked on a job site, I would have suspected the ignition wires, but it's been in my barn, with no one around to sabotage it. I'll check the firing order anyway.

The plugs appear to be new, but I'll try replacing them anyway, as per Bob's suggestion.

If this engine had a timing chain, one of the first things I would have suspected would have been that it jumped a tooth, but I don't think that's possible with timing gears. The only way for it to jump would be for a tooth to break, and then the gears wouldn't engage at all. I will check the timing, but I've been putting it off until I exhaust all other possibilities because in this installation, the timing marks are not very accessible. I'm not even sure I'll be able to see them without pulling the engine.
 
Having a mag the first thing I would do is pull the cap off of mag and check if it has any oil in bottom of cap from seal leaking and getting on points. Having set for a while seal may be bad.
 
The seal in question would be reference#63, part # 31-G3861
a278671.jpg
 
I replaced the plugs. No change. I noticed that the plugs in both the original engine and the replacement engine were gapped at .018, so I tried them that way as well as the .030 the manual specifies. No difference. With the plug out and lying on top of the engine with the plug wires connected, I get spark on all cylinders cranking with the starter, (in this installation, there's no room for a hand crank) so the magneto must be doing what it's supposed to do. I know it's possible to have a spark that looks good, but not strong enough to fire under compression, but how do you test for that?

I checked the firing order, and as I assumed, it hadn't been tampered with.

One of my friends went to an engine show last weekend, and someone there told him to use a tank of fresh premium gas. I'll probably try it even though it doesn't make sense. I know a lot of people (myself included) use premium gas in engines that don't get run enough to burn a tankfull in a season. The theory is that the premium brands that don't contain alcohol keep better, but for fresh fuel, it shouldn't make any difference whether it's regular or premium. This can't be a very high compression engine. What is the compression ratio? That's one spec I can't find in the manual.

About the only thing left is timing, but that can't have changed either. A timing chain can jump, but gears can't do that without stripping teeth, and then nothing would turn.

I must be missing something really obvious, but what is it? I'll feel foolish when I find out what it is. Any more ideas?
 
Have you done a compression test? It's COMMON for a valve or two or three to stick open when these 'ol beasts sit unused, but one would expect at least a couple of cylinders would be firing!
 
As I mentioned in my second post, I followed the instructions in the manual to get compression. Still wouldn't start.

It is firing. It just won't fire consistently enough to catch and run. I can't tell whether every cylinder is firing, but I suspect they are, because there's spark on all cylinders and none of the plugs come out wet.

It has a Wico magneto, if that suggests anything else to check.

The most puzzling thing is that it started and ran fine after being stored, probably for years. It ran when the seller demonstrated it. It ran after I installed it. I test-started it a few times, then used it for about half an hour. No problem. A month later, no start. I suspect that the problem, whatever it is, isn't related to storage. The month that it was out of use was nothing compared to the time it was stored before I installed it, or even compared to the time the old engine was out of service every winter. It always started easily in the spring, with no need to put oil in the cylinders.

These engines have a well-deserved reputation for running no matter what is wrong with them. The engine I replaced started and ran almost smoothly. It just burned a lot of oil because it had a hole in #3 piston.
 
I have a VF4D Wisconsin, If the engine sits out side it can get water in the magneto. Also clean or file the points.
My engine is on my wood splitter and some times it will sit for a year between usage. It usually starts wright up with no problem and then
sometimes it does not. I have had the engine over 40 years and still runs great with normal maintenance.
I bought the engine brand new on a freight claim. I paid $6.00 for it.
Brian
 

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