Hyper Alert: Engine Damage (ring/cyl wear killing ignition to running carb'd engine)

[Christ]

Originally Posted by gjgerhard

Yes, that's right, it's a fairly conventional carburetor. I thought about setting it so that the butterflies close completely, but there are at least two possible downsides to that approach that I can think of: one, shutting the carb completely will result in vacuum levels never intended...that would probably work the valve seals harder, among other things, and two, I believe that at least some carbs have a "dribble" port below the butterfly...the increased vacuum would suck that one harder, maybe even making the problem worse.

As you point out, letting it get down to idle is one way to avoid this problem. The other is shutting off the fuel. That is how diesels are stopped normally, and I remember that my Piper (Lycoming) had a fuel shut-off as well (Marvel updraft carb).

Sure, you can shut off the fuel, as long as you do it with an electronic solenoid that closes the main jet in the bowl. (Manual works, too). Otherwise, your engine will keep running until the bowl is empty, which isn't good, either.

[orange4boy]

So... Did you save enough money from the amount of gasoline saved to justify the expense of the engine damage?

If not, it's called 'false economy'.

Obviously not in this case, but if you could commodify the lowered emissions, then it would depend on that calculation. The carb folks here are a dwindling breed so you won't see a lot of this problem.

Not everything we do here has to pay for itself.

I'm quite happy to pay for a used starter if mine ever dies from EOC and I am confident that if it does quit, by that time it will have paid for itself.

Generally speaking a hypermiled car should actually last longer due to better care and attention and careful driving.

My personal savings to date? $625

[Ryland]

Originally Posted by Christ

Sure, you can shut off the fuel, as long as you do it with an electronic solenoid that closes the main jet in the bowl. (Manual works, too). Otherwise, your engine will keep running until the bowl is empty, which isn't good, either.

The Honda civic carburator has fuel cut off that turns the fuel off when you kill the engine, it does this with 4 valves on the carburator, it also does this when you engine brake, as in when you are going down the hill and take your foot off the gas.
This is why the carburator on the civic is so impressive, of course if you remove any of the 54 vacuum hoses it will stop working correctly and cause horrible engine damage like you are talking about.

[Christ]

Originally Posted by Ryland

The Honda civic carburator has fuel cut off that turns the fuel off when you kill the engine, it does this with 4 valves on the carburator, it also does this when you engine brake, as in when you are going down the hill and take your foot off the gas.
This is why the carburator on the civic is so impressive, of course if you remove any of the 54 vacuum hoses it will stop working correctly and cause horrible engine damage like you are talking about.

This must be something I wasn't made aware of during my time with Honda engines. Do you have a reference for this that I can read?

Still, I imagine that if his carb was working properly to begin with (if his were as you describe), it wouldn't have been dumping fuel after shutting the engine off, so the issue would have been negated altogether.

[Ryland]

Originally Posted by Christ

This must be something I wasn't made aware of during my time with Honda engines. Do you have a reference for this that I can read?

Still, I imagine that if his carb was working properly to begin with (if his were as you describe), it wouldn't have been dumping fuel after shutting the engine off, so the issue would have been negated altogether.

I forget if I found it any other place other then reading the wiring diagram for the Honda civics, if I remember correctly they did it on the cvcc head civics starting in 1976, so the 1.2 liter civic was the only one that didn't have fuel cut off, the fuel cut off is based off ignition switch being on, it would also cut it if the engine speed was over 1,000rpm or 1,200rpm depending on the car, the engine vacuum was high (closed throttle) the car was going over I think it was 10 or 15mph, oil pressure was correct, and I think one other factor as well, but it was part of the engine design to keep it from dumping in fuel when it was not needed.

Either way, killing your engine at anything other then idle seems like a bad idea.

I am one of the people on here who has owned a number of carburatted Honda's as well, including a 1981 civic 1.5 litter dx hatchback with a FE tranny swap, a 1984 civic dx hatchback and a 1985 crx hf and I've spent alot of time reading all of the shop manuals I could get my hands on for them to make sure I understood how they worked so I could be sure to keep the in tip top shape, I'm now on my 2nd civic vx.

[thatguitarguy]

Your Lycoming also has a manual lean out which I would love to figure out how to do on my RV.

I had a couple of early 80's Civics that I would drive hard and heavy full of newspapers through the mountains. Those were good dependable cars.

[dcb]

I don't think this is an issue for fuel injected cars using the key, but for those using a kill switch, they want to ensure they are killing the fuel at a minimum, or taking idle precautions.

[CoastRider]

Need to revamp my kill sw, currently it's a push pull that mimics the action of the key. Seems like 50% of the time when I turn it back on it fires 3 of the injectors even though the engine isn't turning that and I would like the alt and gauges to still function while the engine is being used for braking.

[Bicycle Bob]

Most of the gasoline that was washing the cylinders also escaped as a major pollutant.

[Tweety]

Originally Posted by Bicycle Bob

Most of the gasoline that was washing the cylinders also escaped as a major pollutant.

And what didn't ended up in the oil, making the situation worse over time... Ouch...