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post #1 of (permalink) Old 09-05-2006, 08:53 PM Thread Starter
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Odd starting problem UPDATE - FIXED

Within the last week my 84 Cj7 (258, MC 2100, TFI ignition) has started to act up when attempting to start. Now it is a daily occurance and is predictable.

When I go to start it, the starter spins, and everthing 'sounds' like it is going to catch. I see gas pumping down into the carb when I activate the throttle. But it does not catch. I find that when I hold the gas pedal to the floor after a bit of pumping, about the fourth or fifth try it will start. A bit of white smoke out the tailpipe and then everything runs perfect. Once running it idles clean, runs strong, etc. I tuned it up about two months ago in prep for emissions, plugs, cap, rotor (TFI stuff), cleaned the K&N filter, verified timing and vacuum. So I am confused. It does not seem electrical in that I can hear the starter spin. I see gas, it gets air (it does the same thing with the air cleaner off). I can recreate the situation at will. Shut down the engine, wait a couple of minutes and then again I will have to mash the accerator to the floor, crank four or five times, and then bingo it starts. It does it morning, noon, and night, not a temp issue I presume. So what am I missing here? I don't think it is bad fuel. I am trying to get to the basics (air+fuel+spark = start).

All advice, comments, questions, and witty insults appreciated.
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post #2 of (permalink) Old 09-05-2006, 09:02 PM
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Re: Odd starting problem

By the fact you can start it by mashing the pedal down, sounds like the carb is leaking fuel down. Mashing it helps more air get in to start it. The smoke verifies that.

Yes, you'd think it would be black smoke - some of it is, but lots of fuel cranked into the exhaust system without burning - the white smoke is vaporized fuel - warmed, but not ignited. Black means it partially burned.

The floats have sunk or the bowl is cracked or leaking.

Try swapping in a new set of floats.

Caution - the foam type floats have a thin coating on them to seal them. Touching them with your fingers can cause that coating to dissolve. Best use a paper towel or something to not touch them during installation.
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post #3 of (permalink) Old 09-05-2006, 09:10 PM Thread Starter
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Re: Odd starting problem

RRICH,

That makes perfect sense. I have an extra float lying around so I will try that now. The cracked carb body would certainly be less fun to deal with.

Thanks for the advice. I will let you know what I find.
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post #4 of (permalink) Old 09-05-2006, 10:16 PM
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Re: Odd starting problem

If you pull it off - there might be little lead plugs on the bottom where they drill the passages, then they plug the outer end.

Sometimes they get loose and leak. JB weld smeared over them works great - clean and rough it up first. But - there not be any on that carb - I don't remember.
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post #5 of (permalink) Old 09-05-2006, 10:39 PM
 
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Re: Odd starting problem


Does it crank a while, then 'catch' as you let off the key?
If so the 'Start' circuit isn't working in your igntion module for some reason.

If the float sinks, you will have fuel comming out of the float bowl vent.

If it were seriously flooding, for what ever reason, the plugs would get wet and you would have to let it sit for hours to dry out the chambers...


Black smoke, too much fuel.
Blue smoke, oil in the chamber.
White smoke, antifreeze in the chamber.
Steam, water in the chamber.
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post #6 of (permalink) Old 09-06-2006, 10:43 AM Thread Starter
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Re: Odd starting problem

Junk Yard - I am familiar with what you are saying about the start/crank circuit issue. I did have that exact problem with another CJ of mine and I was able to start it by letting the key 'snap' back. This does not appear to be similar. I have tried to see if I can force it to start by snapping the key back. It still seems to only start on the fourth or fifth try/crank by holding down the gas pedal.

I did replace the float and that did not solve anything. Now I can shut off the engine, wait a few seconds, and the exact same thing will occur, requiring four or five crank attempts. If fuel we leaking down would it occur this fast after shutting the engine off?

Could it be a flat spot on the starter and it just takes a few tries to get it in the right position to engage?
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post #7 of (permalink) Old 09-06-2006, 11:02 AM
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Re: Odd starting problem

The smoke colors - yes, and no.

I'll explain it a bit better.

Black smoke indicates the fuel is burning, just way too rich. But it has to burn to be black.

Raw gas, just vaporizing (hot but no fire) but not actually burning steams off white in color.
Just like when you toss on more charcoal lighter on a hot BBQ that went out - and it doesn't light yet. It steams up white vapor - then when you toss the match - Whoosh! Once it starts burning the carbon is liberated from it and it burns black at first. But it takes actual burning to get the black.

Soo - if it's dripping bad when he stops it, that extra fuel gets down in the chamber, wetting the plugs. As soon as he cranks it, some of that raw liquid gas gets out the exhaust valve at first - liquid, unburned. After cranking a moment with the throttle open the plugs clean up enough to start firing. Once it starts firing - it's still too rich - it makes the black smoke - and the gasses are hot but not so hot as to get the raw gas in the exhaust to catch fire - so it just vaporizes to the white steam. The first puff out the pipe is white, then black, just like he described.

As the float begins to sink over time, the fuel level rises in the bowls. If it's just sinking a little, the level rises only a little. That can be enough for it to spill over into the main wells, but not quite high enough to come out the vents.
So when it's running it's a little rich all the time. Shut it off, that extra level spills into the wells, and the residual pressure in the fuel lines keeps on feeding more into the bowl until it's depleted. That could be almost a 1/2 a cup of fuel!

Usually if the bowl level is high enough to spill out the vents, it won't start, and if it does, it runs really bad.



But then like you said, it may be as simple as the bypass circuit - the wire might have fallen off the solenoid if it's a push-on type.


He He - nowdays with fuel addatives, cat converters etc, the old diagnosis by color can lead us astray.
We used to look for that beautiful blue gray exhaust pipe - now if we get it we have problems. Black is the word, but you actually have to feel it to make sure it's not sticky/oily!
It used to be the same way with a mild grey plug, now it's brown!
Super Clean plugs meant a tad too lean - now it's good!

Too much oil in a Cat that still works comes out black smoke.

(Look at an old oil burning smudge pot - black, not grey.
Sooooo - that means computerized cars with cats are just glorified smudge pots now!

This new technology - it may be good, but it comes with new rules!
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post #8 of (permalink) Old 09-06-2006, 11:07 AM
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Re: Odd starting problem

Unburnt fuel and oil will each leave a residue in the tailpipe; they can look similar. If you wipe your finger around the inside of the tail pipe oil will feel ... well... oily. Unburnt fuel will have a velvety feel to it, and not a greasy - oily feel.

So, there's another way to tell if the engine is blowing fuel or oil.
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post #9 of (permalink) Old 09-06-2006, 11:23 AM
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Re: Odd starting problem

[ QUOTE ]
Could it be a flat spot on the starter and it just takes a few tries to get it in the right position to engage?

[/ QUOTE ]

What we have here is a failure to communicate. (Actually multiple since JYG got involved.)

That’s where I thought you were going when I read your original post but then you went into fuel and all that. Does your statement, “But it does not catch.” refer to the starter engaging the flywheel or the engine starting even though the starter is cranking it over? Does the starter crank the engine over on every try?

Based on your question above, and that it is a 258, and that 258s are notorious for oil leaks at the rear of the valve cover, and that the oil from said leak is slung around by the flywheel, and that dirt gets stuck in the oil … I think you get the picture.
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post #10 of (permalink) Old 09-06-2006, 01:09 PM
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Re: Odd starting problem

He He -- For sure LEVE - look, feel, smell -- but I draw the line at tasting!

What do you do if it tastes like p-nut butter?
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