No spark @ #1 plug - IH140 - Update

I posted last week about lack of consistant spark at the #1 plug after the engine warmed up (after about 25 min). Tractor would start sputtering and lose significant power. Went through the elec system and found the electronic ignition pickup had loosened. Tightened up and same thing, but now had steady spark on all plugs. Last week replaced SPlug wires (also coil, plugs, dist cap, & rotor, and cleaned the fuel lines, strainers and replaced the sediment screen and gasket). Reset valves. Same thing. IH dealer said he was sure it was in the ignition system and sold me a 3 ohm resistor which I tried in the ig wire to the coil. I didn't think it would work but I had to try his advice. No change. I just don't know what to do next.

Problem started again this morning before tractor had warmed up. So now I'm thinking there might be a valve problem, or worse. Anyway to tell if one is sticking or burnt? Compression test? Yank the head? The #1 valve rocker arm has some side to side slop and it and looks like the washer in front has some wear, but I can't make it miss the valve stem. Thanks in advance for any advice.

Does giving it a little choke when it's sputtering make any difference? Maybe running too lean?

Tried that. No help. Is there a way to adust the carb?

Terry: Remember, you didn't convince me electronic ign was trouble free.

Check for air leaks past the intake manifold gasket. To do this, spray some penetrating oil around the gasket area while running. If the engine changes speed, tighten or replace the gasket.

In your original post you said you checked with a meter and there was intermittent spark on number one. That definately falls in the electrical category.
Now you are saying there is an intermittent miss in number one, which is a totally different problem not neccessarily electrical.
My suggestion is to start from square one and totally eliminate any possible electrical failure. The first thing I would do is let it warm up on a totally dark night or inside building and then check to see if spark is jumping arc anywhere. It just sounds to me like something is grounding after it gets warm.
Dell

Assuming the misfire doesnot travel with the sparkplug (changing holes) and assuming it is not wires or anything like it, And assuming it is not the rocker arm, I would get it good and warm (and missing) then do the compression check.
Internally leaking intake manifold can alsop make it happen. JimN

The missfiring of the #1 plug is no longer happening according to the timing light. All 4 give a steady strobe.

Just finished a compression check. 150 - 155 psi on 2, 3, & 4. No. 1 was 125. Went to recheck #1 and realized the fitting wouldn't bottom out (i.e. it wouldn't seal). Then I realized the plug wouldn't go in but a couple threads either before stopping. So it looks like threads have been crossed somewhere along the line. The electrode gap end of the plug stops a long way from the cylinder ID. Could this could be the problem? I've not paid attention to this in the past. Maybe there's different problem with #1. 125 sounds pretty good but it's still 25 below the rest. Or maybe it's just a sealing issue.

Can I run a reamer / tap in to clean up the threads without yanking the head? Looks to be 11/16ths thread. I'll check the neighbor and buy one tomorrow if he doesn't have one. I'll report back. If this doesn't fix it I'll run the other checks suggested. Thanks for all the good thoughts and suggestions. I'll report back.

The spark plug holes are metric threads, 18mm.

I got a sparkplug thread tap from NAPA to clean out thread holes. As Owen said---18MM. Cost was $6 or $7--so won't break the bank. Also check for crud build-up where the plug seats.

I was thinking manifold leak, a little choke might compensate. Don't know anything about the carburetor on those.

NAPA was closed so I borrowed a neighbor's 11/16 (0.02 in. less than 18mm) tap and ran it through. Compression meter fitting now bottoms out as does spark plug. #1 compression now 150 psi, same as the rest so this is not a valve/ring problem. Tractor smoked a good 20 minutes after cranking while all the crude accumulated in #1 cyl burnt up.

Cranked it again last night (in the dark) and could see some sparks jumping around #1 plug wire (arcing to neg pole of coil where it was touching) and at #2 plug. When I shut it off I was still seeing light between #2 plug and wire cap and I think I heard crackling (faint). I'll have to replace some wires later this week. I also think insulation on the pos/neg terminals of the coil would be in order. Still, tractor sounds much better.

In summary, the problem was in the ignition system (loose electronic ignition pick up, and SPlug wiring) and a cross threaded spark plug preventing it from seating. Cross threading might have happened during the trouble shooting. I'm going to be looking for better wiring. The little brass crimp on fittings at the distrib end of the plug wires are really cheap. Any one know where to get some good heavy duty SPlug wires?

If you can find a set of STANDARD spark plug wires for a late 1970's or early 1980's 4-cylinder car or truck at an auto parts store.

Problem is the stores don't stock wire sets for older vehicles. We went through a dozen or so before we found a set for a Chevy Corvair in stock. The wires were too long but we made do with the shortest four wires.

Since he has electronic ignition, why is it necessary to have 'standard' plug wires? (Is that opposed to 'noise suppression'?) I have 1966 140 with Pertronix ignition and I am ready for new cables. I have copper on there now from before the Pertronix. Sorry for the hijack, but this is relevant for OP, too. What should we really use with the electronic ignitions?

Durk, Do a archive search on this subject. There was a lot of discussion on this last fall and I am sure you will get some good info.
Dell

Durk - The $11 set of plug wires from our local case dealer have super cheap connectors you crip at the distributor end, and insulation at the plug end is pretty thin. Sure seemed like a lot of sparks jumping around in the dark with the old wires and 2 new wires. I have the flame thrower coils (40k volts), so maybe I need better wires.

I ordered 2 sets of custom high performance plug wires made for IH 140's from the Brillman Co for $16 ea. They have the heavy duty MSD style connectors at the dist end, and insulation at the plugs is heavier. I think they will work well. I'll try them this weekend.

(quoted from post at 08:29:44 05/11/09) Since he has electronic ignition, why is it necessary to have 'standard' plug wires? (Is that opposed to 'noise suppression'?) I have 1966 140 with Pertronix ignition and I am ready for new cables. I have copper on there now from before the Pertronix. Sorry for the hijack, but this is relevant for OP, too. What should we really use with the electronic ignitions?

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Electronic ignition doesn't necessarily have anything to do with solid/ suppressor wire, although the hopefully hotter spark on an electronic system should help offset suppressor wires. If I wasn't concerned with radio interferance, I'd run solid core wires period.

(quoted from post at 19:51:13 05/11/09) Durk, Do a archive search on this subject. There was a lot of discussion on this last fall and I am sure you will get some good info.
Dell

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Unfortunately, since I have six years on this forum, I HAVE searched, thank you, and I find those who insist on copper and others who say copper should not be used on electronic ignitions. If I missed a definitive discussion, please point me to it because this forum's spastic search function is not going to get me there.