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Discussion Starter · #1 ·
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FIXED - UPDATE

The problem has been resolved by installing a new Ignition Module

Thanks to everyone who helped me trace this down.

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Ok, so I am having a strange starting problem on my 84 CJ7, 258, TFI ignition, 2100 carb.

Here is the sad story. Most mornings when I go to start the jeep it turns over on the first crank. I drive for about 30 minutes on the highway. I park the vehicle for about 20 minutes and when I go to start it, it won't catch. The starter turns, and everything seems to be on track but it never hits. I try to start it about five or six times and eventually, just before the battery dies, it starts. The pattern is always the same. Great in the morning, but difficult after having been run. In the evening the same thing happens.

I have tried jumping it during this problem and it does not seem to change anything thus I believe the battery is fine as it is only about six months old. I changed the selenoid as I had a spare and this made no difference. The terminals are clean and good contact on the battery. The fuel filter is fine and the carb has gas (opened it up to inspect the float level) pumper pushes two nice streams of fuel into the carb throat. I thought it might be vapor lock but that is not it. As it does it regardless of temp. Also, I have removed the gas cap during starting attempt.

Sometimes it will hit and start immmediately, other times i have to try six or seven times. Once running it purrs like it has always done and does not seem to have a problem. I have not yet had the starter tested but it is relatively new (I know that is no guarantee, but?). The fly wheel was replaced about 10,000 miles ago and it is not acting like a flat spot on it or the starter. I am miffed. What am I overlooking.

This started about a week ago and is gradually getting worse. I am certain that in the very near future I will not be able to get it started some time.

I have found that if I hold the gas pedal down and release the key (snaps back) that sometimes does the trick. That could be coincidence though.

I have not tested the coil (don't know how) but I wonder why it starts some days just fine.

Any ideas where to look, what else to test? I am out of ideas.

Thanks for all your help.
 

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Re: Odd Intermittent starting problem

Maybe it is getting flooded. Hold the gas all the way down as you try to start it.
 
G

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Re: Odd Intermittent starting problem

Get back to basics.
Do you see black smoke going out the tail pipe when it does start? Flooding...your carb might be leaking into the intake.

Have you tried raising the hood when you stop to let the engine cool down for 20 minutes before you start it? If this works then you have a part that is getting hot...Duraspark module...coil...Some coils when they get hot, will not work as well.
 

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Discussion Starter · #4 ·
Re: Odd Intermittent starting problem

Will,

It does seem like it might be flooded. It does seem to consistently be starting better 3rd try) when I hold the gas pedal to the floor. What causes this, or better yet how do I fix. Is this a float problem in my MC2100?

Thanks for your reply.
 

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Discussion Starter · #5 ·
Re: Odd Intermittent starting problem

DDawg

It has a slight bit of black smoke out the tailpipe when it finally kicks over. If the carb is leaking into the intake where is the problem? The float, needle seat?

Thanks for your help.
 

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Re: Odd Intermittent starting problem

I used to have a MC2100 on a 360, and it used to do the exact same thing. I messed with and tinkered with it, and sometimes I would fix it for a while, but usally in a week it was back to this game.
Next time it doesn't start for you on the first try, stop cranking, give it about 1/2 pedel (that is what my old 360 used to like) and try and start again. Worked every single time for me. It may take some playing with for you to find just where your jeep wants the pedel. Since mine ran good once it was running, I just left it be.
 

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Re: Odd Intermittent starting problem

Float might be too high but I suspect you don't have a return line. The fuel is probably being boiled past the needle and seat.
 

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Discussion Starter · #8 ·
Re: Odd Intermittent starting problem

Ok, so heres the thing, the carb has been on my jeep for two years, running great. I have a fuel return line. Nothing has technically changed recently.

So I thought it was pointing to a carb flooding problem so what the hell. I buy a rebuild kit from NAPA and spend a few hours doing it right ( I have done this at least three times). Seal it up tight, make sure no vacuum leaks. After the first few starts I drive for about 15 minutes, everything feels great. Go back home shut it down and boom, exact same symptoms. It won't start unless the pedal is to the floor and only then after about three or four crank attempts. What the hell? Now what? It still is acting like it is flooding. How is this possible after the rebuild of all core parts (power valve, seals, pump, etc.).

It just doesn't sound like anything electrical to me. Any other ideas? It is not hot around here today so again I doubt vapor lock.

Help if you can. Thanks...
 

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Re: Odd Intermittent starting problem

Are the floats fuel logged or have the absorbed so much fuel that they don't rise as high as before or if they are brass, could they have a leak and filled with fuel? Did you replace the needle and seat for the float assembly.

What direction is the fuel filter mounted in reference to the return line port.

Is the return line plugged? can you blow into it easily?

Heat also effects electrical parts. The sensor in the distributor can just be putting out enough signal to run the engine but when it gets hot and the voltage drops from cranking then maybe your not getting enough signal. This is easy to check, just pull a wire off a spark plug and see if your getting a good spark when you can't start your jeep.
 
G

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Re: Odd Intermittent starting problem

With it sitting there, pull the top of the carb off and check your float level. When you look at the floats, the tops should be about parallel with the fuel....if I remember correctly, about 1/3 should be above the fuel.
You can also get a good idea if the level is too high by just looking at the fuel level.

But I would like to point out that a fuel float problem usually causes running problems as well.

When it does start up, does it have that 'lug lug' sound that is typical of a flooded engine? To be that hard to start...assuming it is flooded....I would expect a lot of black smoke.
 

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Discussion Starter · #11 ·
Re: Odd Intermittent starting problem

The float is brass and I tested it for leaks and it is ok. The level looks good and I agree with DDawg, it runs way to well for the float to be the problem, this is only a start issue. And it appears to be getting worse daily. At first I thought it had to do with the heat or running the engine. Now I find it difficult to start after it has sat all night long also.

I am now leaning toward this being an ignition module problem. I have read several old threads related to not starting issue and I also received an email telling it was the module and why.

The main reason is that while it does seem to occaisonally start with the pedal to the floor, the trick seems to be allowing the key to 'snap' back to the run position at the right time. This would then appear to be a weak or no spark condition during the cranking operation. At least that is what I am now working towards.

I need to check the wiring from the ignition module and the coil to see if anything 'smoked'. Also I quess I can get a replacement module. How could I do a definitive test on the module to determine if this is the culprit?
 
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