Wicked issue with 4AC

[el_camino]

Hello guys, I am trying to build love to a good condition AE86 with 4AC and keep it original for the moment. 

There is not logical issue however and being out of ideas I am reaching out for help.

The cylinder one refuses to work, no matter what.

There is spark, a good one. Distributor revised.

There is fuel. Tried with different carb from working 4ac.

There is good compression on all 4 (12).

Valves have been adjusted 3 times and are in spec.

The car is running smooth on the other 4 otherwise, starts first try. Runs rich, I assume due to the not burned fuel in cylinder 1.

I am really out of ideas what to do next. Anyone had a similar problem and ideas for testing please?

 

 

Edited 11 hours ago by el_camino

[altezzaclub]

Tricky... So is the cylinder ID from pulling a spark plug lead off when running? Number one didn't drop the idle speed?

What were the compression readings?

Is the spark plug black or clean? Colours of the other 3?

..and Cyl 1 will fire a spark plug in its lead resting on the head?

 

 

[el_camino]

All leads are new and all spark plugs are new as well as the distributor cap. 

Indeed, pulling the cable off the cylinder 1 doesn't change the work of the engine, while pulling any off the others would nearly stall it (two cylinders left).

Swapping spark plugs or leads always keeps the first not firing. 

The spark plug on cylinder 1 turns wet and black. The one on #2 is rather black with a bit of brown, the others are rather brown 

Cold compression test reads 11.7 on #1 and 12 on the rest. Warm compression shouldn't be as far from this to the point to fully not ignite cylinder one.

Edited 3 hours ago by el_camino

[altezzaclub]

have you checked this one- '..and Cyl 1 will fire a spark plug in its lead resting on the head?'

Just to make sure the plug does fire on the lead, which it probably does.

So, has fuel, has spark and has compression.. The compression is the worry, a broken ring would drop that compression before stopping the plug firing. A head gasket might drop it enough to misfire but you would expect to see that in the compression test. Sort of 110psi for a dud cylinder, and your #1 is only 5psi down.

No oil in water or water in oil?? They usually fail between 2 and 3 or 3 and 4 but maybe cyl 1 is leaking out somewhere... Which is what the Brave AI didn't specify.. 

"The Toyota 4AC engine is notably prone to head gasket failure even from minor overheating events, without necessarily reaching the red zone on the temperature gauge. "

I didn't know they were prone too HG failure until I thought to check.

So, check a definite visible sparking of a plug on #1 lead. No water in oil, oil in water or bubbles in the radiator on cold start... and list anything else you can think of.

How did it start? Just one day never ran on that cyl, or were there oncoming signs of misfire?