1991 Accord 4 cylinder starting issue

Last week it just wouldn't start for a few minutes. Cranks fine but doesn't start. A minute later it works fine.
A few days ago in my driveway it starts but dies as soon as I release
the key, several times. I try it again a few hours later, same thing. I call the tow truck, he comes, tries to start it while flooring the gas. It explodes to life releasing lots of smoke (black I guess). he slowly lets up on the gas and it stays on at idle. I drive it to the mechanic, and there is nothing wrong. Starts each time.
The mechanic calls me back an hour later saying that he remembered that if this happens again, open the gas cap and stick a finger into the metal ring to make sure that air can get in. Apparently he learned this trick a while back.
So, any idea what is going on? Since it does catch, it doesn't seem to be the ignition switch which was my original guess. And it has worked fine the last few days. Just a fluke?
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4ax.com:

This sounds like the typical Main Relay problem.
When the engine dies, do all the dash lights come on, or are they dark?
--
Tegger

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On 09/10/2013 06:09 AM, dgk wrote:

it could have been one-time flooding, spark plug fouling, etc. now it's running, all the excess fuel's gone, the plugs have cleaned themselves, and you're back to normal.
or, as tegger says, it could be main relay. but that wouldn't explain the black smoke because if the relay's out, the injectors don't fire, and black smoke is excess fuel. but fix the relay anyway, just to eliminate it from being a future problem. tegger has an instructive page on how to do that at tegger.com
--
fact check required

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It's been fine since then, although I only use it once every few days. I'll take a look and see if I can find the main relay - I did have it replaced a few years back - or maybe five or six years back. Something like that, the years all just seem to flow together.
I'm guessing that the burst of smoke was just because of the previous starting failures; normally the thing doesn't use any oil at all.
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On 09/13/2013 05:54 AM, dgk wrote:

new ones are normally good for longer than that - if you've had it replaced, you should be good for another 5+ years.

that's what i think.
as to difficulty starting, what plugs do you have in there? i've just had yet another episode with bosch insisting on reminding me they make the most unreliable plugs on the planet. if you have them in your car, swap them out for ngk.
--
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Somewhere on teh intarwebs dgk wrote:

It wouldn't surprise me if the fuel tank's pressure relief valve is playing up resulting in hinkey carby levels until the thing's been booted a bit and fuel level settles.
Black exhaust smoke is usually caused by a very rich fuel mixture rather than oil. Oil tends to be blue.
If in fact the pressure relief valve hadn't worked properly (as suggested by your mechanic) when the fuel warmed up it may instead have been pushed into the carby resulting in high float levels and even pooling in the inlet manifold. Revving the heck out of it would clear this fuel and allow it to run fine. Was it extra-hot during the time it wasn't started? Or perhaps it's jus now the vent decided to play up.
I suppose you're going to reply that it's injected now and trash my theory?
--
/Shaun.

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On Sun, 3 Nov 2013 12:23:24 +1300, "~misfit~"

There was nothing unusual about that day. Normally the car sits for several days in a driveway that slopes pretty steeply downward since the garage is basement level and that was likely the case at that time. Since I was supposed to be driving to tennis, that means it was a Saturday morning and the car had probably been sitting for at least two days.
I think it is fuel injected.
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