S11a no longer starts...!

[pepe]

Here is my dilemma:

1. engine ran great one month ago at temps above freezing.
2. The temp is now below freezing and engine will not run.
3. time checked and witnessed to be correct. 3-6 deg BTDC using strobe.
4. backfiresout exhaust periodically when turning over, and shoots smoke out of the carb every revolution.
5. have pertronix ignition and strobe shows spark to be occuring consistently each rev.

What i have tried.

• checked sparks: look wet but each one sparks when touched to engine block and engine turned over.
• assumed rich, so completely closed idle jet and tried starting with starting fluid only. (first purged engine by turning over). no indication of firing at all.
• put idle back to original location, and advanced/retarded dist. (used knob on 25D type). still back firing and carb puffing smoke.
• carb top removed and float moves freely and floats. I've done this numerous times before and have had not problem with running after reassembly of carb.

could something be freezing and making engine run rich? is it running rich?

any help greatly appreciated.

Erik

[Daurie]

If you definately have the correct timing I would suspect valvetrain problem. With the backfiring and the fumes out the carb... could be stuck valve / valves.

[4flattires]

You have spark, you have fuel (starting fluid). Fall back to the basics and do a compression check.

Jeff

[jp-]

If you definately have the correct timing I would suspect valvetrain problem. With the backfiring and the fumes out the carb... could be stuck valve / valves.

I concur, something is off. Backfiring out the carb / exhaust can mean that the timing is off (spark not firing at the right time) or that there is a valve / timing issue.

Also agree with Jeff. If compression is not strong, do further inspection on valve train. If compression is normal (or >100psi) inspect timing.

It is possible that you may have flooded the engine as well. This will mean taking the plugs out and letting it sit for a while, also each plug must be "burned" off, with a lighter or a torch until it is completely dry. If you are in a hurry to dry out the cylinders, you can use a long barbeque match to light them off, but be VERY careful using this method.