starts hard. runs rough for a minute.

[taylor]

Hey Everyone,

Over the past couple of months, my engine has been developing a problem that is slowly getting worse.


The symptoms:

If the engine hasn't been started in more than two days, it starts hard. It requires cranking a few times, and when it does start, it runs rough (like at least one cylinder is not firing) for about a minute. After that, it runs just fine, and starts immediately when cranked.


My diagnostics:

I've tried adjusting the idle settings on the carb, and that has not helped. The choke is fully engaged.

Yesterday, the engine wouldn't start at all. I tried changing the spark plugs and disconnecting the exhaust. Neither of these caused the engine to immediately start, but it did eventually start. It ran rough for a minute (with black smoke in the exhaust) and then ran fine.

I let it cool off, and then started running tests. My theory was that the engine seems to be getting spark and fuel, so the likely culprit is a compression issue. Perhaps the head gasket is blown, and once the metal heats up, it expands enough to seal the joint between the head and block.

Compression test showed 80 85 83 90. This is not conclusive, but it was also run only a couple of hours after the engine had previously run. The problem is manifesting after the engine has sat for a couple of days.

When running the compression test, plugs 1 and 2 were wet but clean. Plugs 3 and 4 were wet and sooty. These were plugs that had been run for only a couple of minutes.

I then started the engine. It started right up, but was running rough. I unplugged the first spark plug cable: no change in sound. I reconnected it and unplugged the second spark plug cable: no change in sound. I reconnected it and unplugged the third spark plug cable: it shocked me, causing me to drop it into the engine compartment. I immediately shut off the engine. I think the engine sounded worse at that point, but I was paying more attention to getting the thing shut off before anything shorted.

It seems to not be a starter issue, since the engine runs rough even after it starts. I'm not sure whether I should be more concerned about the spark plug cables that didn't shock me or the one that did. (The ones that didn't shock me were on cylinders that seemed not to be firing at the time. Given the high voltage coming from the coil, I'm not sure whether one expects to be shocked by these cables.) The engine has points, and it is a 1-year-old rebuild from a marine mechanic. I assume that he set the gaps and timing when he rebuilt the engine. It ran really well when I got it. I had an overheating event in July 2013, but after replacing the wet exhaust, and installing a thermostat and high temp alarm, it has run just fine since then. Volt meter shows normal battery power, and oil pressure is fine.

I'm not sure if there are any other tests I should run. What would cause an engine to run poorly at first but would stop having an effect once the engine gets going?

[hanleyclifford]

You may be getting some kind of buildup in the carb idle passages. Have a look at whats in the carb bowl by draining the bowl into something clear. Another quick fix is to remove the idle adjusting screw and then blast starting fluid or carb cleaner into the hole.

[taylor]

Thanks Hanley. I'll give that a shot.

Any thoughts on the shocking spark plug cable?


t

[Dave Neptune]

Info

Taylor, you state the choke is engaged. Is it engaged when running rough? Have you tried releasing it when the engine begins to warm up?

Your compression numbers are fine for running smooth if all else is well so don't worry about the head.

My guess at this point would be a sticky needle and seat or a plugged air bleed in the carb. Just sounds like t way to much fuel!

Dave Neptune

[JOHN COOKSON]

Run the engine at night in the dark with the spark plug wires in their normal or working position and check for arcing. Some advocate misting with water during the test.

Have a look inside the distributor cap for tracking or any other funny stuff going on. Check the rotor too. Also check the terminals on the cap where the plug wires push in for corrosion.

You can remove the back flame arrestor and hold your hand over the carb throat for a 100% choke. If this makes the cold starts easier then you are a bit lean on the cold starts. You'll need a crew or a remote starter switch to do this.

TRUE GRIT

[taylor]

No, I'm letting out the choke as the engine allows it.

I'll check out the carb this evening. (If it makes a difference, I have a racor filter/separator as well as a polishing filter. Both are ~1yr old.)

[hanleyclifford]

No, I'm letting out the choke as the engine allows it.

I'll check out the carb this evening. (If it makes a difference, I have a racor filter/separator as well as a polishing filter. Both are ~1yr old.)

It does; the polishing filters at 10 micron are easily clogged by debris from a new-to-ethanol fuel tank. The filter should be changed at least once a year in any case.

[romantic comedy]

I am thinking that the plug wires are connected wrong, maybe.

i would be concerned about not getting shocked.

[taylor]

Okay, so:

-All the spark plug cable, distributor, and coil connections look shiny and clean. The outside case on the coil is rusty, but that's about it.
-I ran the engine in the dark: no arcing.
-I pulled the distributor cap. It looked fine in there. The connections all had a little green on them, which I cleaned with some steel wool. I'm not sure what "tracking" is. I turned the engine over by hand and the rotor spun.

The engine started on the second try. She ran rough for 10 seconds, then ran fine. I pulled and replaced the first and second spark plug cables, there was a definite change in sound this time for each of them (although they, once again, did not shock me).

I can't find my carb cleaner, so I'm going to buy some. I'll clean that out tomorrow.

Is the bowl of the carb the same thing as the float chamber? Do I empty it by unscrewing the main passage plug?

[hanleyclifford]

Bowl=float chamber. Just unscrew the plug and drain into something clear. Don't drop gasket.

[edwardc]

An engine that starts hard and runs rough after sitting for a few days, but smooths out after a few minutes; this sounds like sticky valves to me.

Try doing a compression test on the cold engine after it's sat for a couple of days. Then repeat the test after warming it up till it runs smooth. If it's sticky valves, one or more cylinders should show a marked improvement in the compression numbers when warmed up and smoothed out.

Remember, when doing the compression test, be sure to remove all 4 plugs, have the choke off, and the throttle wide open.

If it is sticky valves, try running some MMO in the oil (up to 25%), and a small amount of MMO in the fuel. This will get the MMO to the tops and bottoms of the valves. It will take some time to free the valves, but it will work.

[Dave Neptune]

Shocking

Taylor, getting shocked by good or bad wires is fairly common. Did you mist some water or even "Windex" at the wires while running? If you did not see a light show in the dark I would assume the wires are fine.

Your cap is suspect to me as possibly "PART" of the problem. Do not use steel wool inside the cap. A small wire brush is better and the brush is less likely to leave any "METALIC" debris inside the cap. If there is any or even a few carbon tracks or bits of the steel wool under it havoc will result. My rule is if a cap is suspect at all I just replace it and the rotor. With the EI they last for many years.
Did you check for the centrifugal advance to be free and functioning when under the cap. Also did you take a look at the gap and/or check the dwell? Also there is a possibility the timing slipped, ie the distributor got bumped while servicing. Making sure the wires are actually in the proper order is a good idea too.

The sooty plugs and roughness also point at the carb and the fact you need the choke also does. I'd bite the bullet and do 2 things. First I'd order up a carb kit and get it redone. Plenty of help here on the forum if yer not familiar with carbs. The thing needed most is a good air gun for blowing through the passages. AND when reinstalling I would add a cheap fuel pressure gage between the carb and the polishing filter. Also remove the polishing filter and replace it!!! Then crack the filter open and take a look inside.

Dave Neptune

[JOHN COOKSON]

While You At It.........

Okay, so:
The outside case on the coil is rusty, but that's about it.

Buy and install a new coil. If you can see rust the bottom of the coil is probably super rusty. If you have an oil filled coil the oil will leak out when it rusts through. Then you will be nowhere fast. It happened to me. I gave the new coil a couple of extra coats of primer and a couple of coats of paint before I took it down to the boat.

TRUE GRIT

S\B While You're At It in the header.

[taylor]

carb + valves + ignition

Guys, thanks for all of your input on this!

Okay, I see this breaking apart into a few separate projects: carb, valves, ignition.

--
Carb:

I'll empty the carb bowl tonight and see what comes out.

I'll get a carb service kit and new polishing filter (and look inside the old filter).

I've only ever adjusted the idle mixture, so I'll definitely need a bit of help with this one. I'll check out the Moyer tutorial video, first.

--
Valves:

I'll also let the engine sit until the weekend and then see what compression numbers I get. If there are no spark plugs in, won't I get a face full of gasoline as the starter turns the engine?

Is cutting the motor oil with 25% MMO the best way of dealing with sticking valves?


--
Ignition:

I set the spark plug gaps when I installed the new plugs. I don't know how to test dwell or set/check the dwell or timing. Is that information in the Moyer Manual? What tools do I need?

I did not mist the wires with water while running in the dark. I will try that when I next run the engine. What would sparks tell me? (That the wires are bad? That the coil is bad? Both?)

If I were to get EI and a new coil, would I also need a new distributor cap, or does that come with the EI kit?

Also, from reading old threads, it seems like I would need to put a lot of thought into determining what resistor to place before the coil (and maybe after the alternator, as well?). Does this issue still exist, or does the Moyer internal resistance coil handle the resistance issue?



In summary: Until further compression testing and a check of the carb bowl contents, it seems like my current symptoms are most likely being caused by sticky valves, but that a dirty carb (and resulting rich condition) contributed to the valves sticking. The coil seems suspect, but that is more of a preventative measure, as the coil does seem to be functioning at the present.

Does that seem correct to everybody?

[Dave Neptune]

One step at a time

Taylor, with the compression numbers you posted and the fact that the engine is still running rough after a bit of warming I doubt you have a sticky valve issue. I am assuming that your plugs being wet and sooty were wet with fuel, correct?
I am a big fan of the EI and it does not come with a cap. If you convert to EI start fresh with a new cap, rotor and wires. I'm not worried about your coil either at this point. Once the EI is installed and the timing set there is almost no maintenance on the ign system. I run 5~6 years on my cap and rotor and 2~3 years on a set of plugs (RJ8-C). Just an occasional check of the "C-adv" mechanism. A far superior system. Most of the coil problems we see on the forum are due to to hi of a charging voltage, thus the resistor. I ran without one for over 20 years and did install one for a test to see if I could discern any performance drops with one. I noticed nothing and it is still installed~~can't hurt.
I do suggest the carb first and touch nothing else. If you find the carb or the filter gumbed up yer' on to something. Until the carb is OK I would not mess with the ign. Once the carb is OK and the compression numbers are good I would then kick the gong and convert to an E/I~well worth the effort and cash.
Whatever you decide to tackle, do tackle one thing at a time. My personal suggestion is first carb then see if the roughness or compression is off (valves) and if the compression is still OK convert to the E/I.

Dave Neptune