Ke55 not running right

[79rolla]

Hey everyone I would like to have another opinion or 2 as to what my troubles might be. I took my 79 corolla out last night and it seemed to be misfiring. But this was only for about 5 minutes of driving. When we got on the highway it come good. But it has done this twice or three times now, and I would like to know what you guys think it might be.

 

Cheers 79rolla 

 

[altezzaclub]

Three questions-

What have you done to solve it so far?

Stock ignition system? Points and condenser?

Does it use water at all?

 

Leaking head gasket will make it misfire when cold, but so can a few other things. Could it be a fault in the choke system rather than a spark misfire?

 

 

[79rolla]

Condenser isn't connected and hasn't been since the engine got put in. But with the Condenser disconnected it hasn't done this before. Points we don't think are 100% but yet again it hasn't really done it before. The last time it acted like this is when I had a nice fireball through the carby. So yeah idk what else or what is doing it. Thanks for a bit of an idea altezzaclub. 

 

Cheers 79rolla 

[79rolla]

Its only on a really cold night that it does it. Or a medium cold night. So below about 20c out side temp is when it does it. It happens with the choke off. Last night we drove for about 5 or 10 mins after warm up.

 

Cheers 79rolla 

Edited Sunday at 07:28 AM by 79rolla

[altezzaclub]

Maybe  a cold engine problem then- so mixture is weak for cold running, or spark weak when cold and harder to fire.

The condensor must be connected for it to run, it builds up a charge of electricity when the points are open and discharges it all at once when the points close, and that rush of power is the thing that fires the coil's high-tension side.

 The important thing is that the condensor and 12v wire from the coil -ve both go onto the points spring strap, and are insulated from the motor. You can pull the points open with your finger and see how bad the contact surfaces are, the sparking causes spark-erosion on one side and it hollows out, and the other side gets a volcano built up on it as the metal is spark-deposited. That gives a false reading on feeler gauges if you are setting the points gap on old points. When you fit new points, fit a new condensor too, as they lose their insulation strength over time and cause misfires...

So check the condensor is connected, that there is no circuit from the moving points arm to earth when the points are open and the key is off, and the points gap is correct and so is the timing. Pull the spark plugs and see if all four are the same colour, maybe you have a dud cylinder.

Then check the choke operation, which hopefully is a manual cable. Fully off when off, fully on when on. When it misfires next time you're driving, pull the choke on slowly and see if 1/4 choke helps, or 1/2 choke. Then you will know its lean when cold. If you have a leaking inlet gasket you should see different colours on the plug concerned, that could also make it miss when cold.

See how you go- do you do your own tuning? ...so you have feeler gauges or a dwell meter, a timing light and a multimeter for testing circuits?

 

 

 

[79rolla]

Thanks altezzaclub. Just pulled the plugs yesterday amd 2 were a little white or white ish. With 1 grey and 1 covered in oil. Timing isnt see 100%, it is just set by eye. Ive changed the plugs twice in the month of may, due to the first time a similar ish problem with misfiring but it was when it was warmed up. And that time was just a fouled plug. But changed them yesterday and they weren't fouled at all. I can confirm that the ignition condenser isnt connected and never has been with this engine. (Engine  been in 18 months) and it never acted up with it disconnected. Anyways, which side does it connect to? The positive side of coil or negative?

 

Cheers 79rolla 

[altezzaclub]

Coil positive is ignition switch, that's where it all gets 12V from. Coil negative goes to distributor and tacho. The condensor joins the coil negative, either outside as in that photo, or inside on the points arm where the black negative wire goes, depends on the dizzy.

So is timing set by putting the crank pulley at 10-15deg before TDC for number one cyl, then turning the dizzy until it sparks? ...or put your multimeter across the points and see the voltage change. Grab a  cheap timing light when you can, they make life easy.

So the plug covered in (fresh I assume?) oil was from the funny K motor 'plug cups' that spill oil down the plug holes when you take them out. So long as they have pretty much the same colour it means the cylinders are working evenly, and a darker one is probably the one that misfires.

Try connecting the condensor and checking plugs straight after it misfires and see if you can figure out which cylinder it is. It might be just a plug lead or the distributor cap.

[79rolla]

Thanks altezzaclub

Its really only when cold outside. Like today its about 20c and its fine. But i will let it cool and see what its like later. Cheers 79rolla