Ignition trouble??????
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From: Kansas
Ignition trouble??????
Hey all, Have a 390 in my 73 f100 that I just rebuilt the carb and gave a complete tune-up. Drove it the other day down the highway and around town with no trouble. Well, today I go for a drive and the thing starts cutting out. I limp the the thing home just over an idle... WTF???? I
noticed it was really hard to start, had to press the accelerator to the floor. When it did start it smelled rich.... The truck will idle but you press the accelerator and at 1200 rpm on the nose it falls on its face. The tach just drops like it has no power. The thing has a brand new fuel pump on it. I'm baffled here.... I'm leaning electrical. Any ideas??? 
noticed it was really hard to start, had to press the accelerator to the floor. When it did start it smelled rich.... The truck will idle but you press the accelerator and at 1200 rpm on the nose it falls on its face. The tach just drops like it has no power. The thing has a brand new fuel pump on it. I'm baffled here.... I'm leaning electrical. Any ideas???
Hotshot
Joined: Apr 2009
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From: Stanley, VA
Sounds to me to be more fuel related than ignition. Check the auto choke, make sure it's completely open.
On ignition, do you still have points and condenser? If so, a bad condenser could cause similar symptoms, along with a bad coil.
On ignition, do you still have points and condenser? If so, a bad condenser could cause similar symptoms, along with a bad coil.
Hotshot
Joined: Apr 2009
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From: Stanley, VA
Check also that the small ground wire inside the distributor was reattached when the points were changed. It should go from the holdown screw on the dist plate to one of the screws that holds down the points.
Some other things to check before replacing the coil. Double check the point gap, should be .017", check the distributor shaft bushings - grab the rotor and try moving it side to side, it should only have minimal movement.
Check the condition of the coil wire, make sure it's fully seated in both the coil and the cap. What kind of shape are the plug wires themselves in? If all that's okay I would try the coil.
In your original post you said that you had to hold it to the floor and when it did start you smelled gas.
It sounds like it might have been flooded. The first thing I'd do is pull the plugs and see if any of them have been fouled by a too rich fuel mixture.
If they check okay, then I would go after the ignition.
In the picture you can see the ground wire just below the coil primary wire.
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From: Kansas
I'm out in the garage right now, sounds like we are on the same page. I checked the dist. and found that the collar had slipped and the timing was off, advanced it a touch and that solved the hard to start issue. It fires but if you touch the throttle at 1200 rpm's the thing sounds like crap. Gapped the points at .017 according to the manual I have and it has a new condenser. It all looks good, no slop in the shaft as well. I have a sun tach that I'm watching and the thing goes crazy as well when the motor hits 1200 rpm. Like it's losing signal from the coil. Noticed this a while back the the tack was a little funny but it quit and I never really worried about it again.
Hotshot
Joined: Apr 2009
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From: Stanley, VA
Check the coil primary wire, the small gauge wire that goes from the coil to the points. Could be that it's broken internally, take a good look at it where it connects to the points.
Hotshot
Joined: Apr 2009
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From: Stanley, VA
Another thing to check, years (decades) ago I had a Sun tach develop an internal short gave similar symptoms. If the coil primary wire checks okay, try disconecting the tach at the coil and see what happens.
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From: Kansas
Ok Mike here's where I'm at. New coil didn't fix it, I reset the points and the thing fired right up and works fine. However, the distributor is noisy as heck. The only way I can describe it is sounds like there is a pissed off wasp under the cap. It seems as though there might be something loose or broke to me. I noticed this noise the other day on my drive.... Before all this happened.. I mean it's so loud you can hear it over the motor and I've got 2 1/4" duals....
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Hotshot
Joined: Apr 2009
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From: Stanley, VA
Check and see if the rotor is contacting the inside of the cap.
The rotor should contact the center coil terminal but it deffinitely should not be contacting the individual plug wire contacts.
Look closely at the cap and tip of the rotor to see if there is any sign of contact.
The rotor should contact the center coil terminal but it deffinitely should not be contacting the individual plug wire contacts.
Look closely at the cap and tip of the rotor to see if there is any sign of contact.
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From: Kansas
Ok, rotor doesn't seem to be hitting but the plate that hols the points and condenser flops around alot... Is this normal????? I really sounds like it's coming from the cap though. I even filed the rotor a bit to be sure. Could the shaft be bent by chance?
Hotshot
Joined: Apr 2009
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From: Stanley, VA
No that's not normal but it's also quite common. The breaker plate is made up of two pieces that are hooked together with a plastic pin and spring. This is to allow the piece that the points are attached to to pivot when the vacuum advance moves. The lower plate is held solidly in place by two screws into the dist. housing and the moveable plate floats on a plastic bushing. All this plastic deteriorates and the plate tends to move around alot.
These plates are still available, you can get them from just about any parts store (assming you can find someone who still knows what a distributor is). They're easy to change too.
As for the bent shaft, that's possible. Pull the rotor, look straight down at the shaft and crank the engine over. See if you can visually see any runout.
These plates are still available, you can get them from just about any parts store (assming you can find someone who still knows what a distributor is). They're easy to change too.
As for the bent shaft, that's possible. Pull the rotor, look straight down at the shaft and crank the engine over. See if you can visually see any runout.
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