I am doing a rather serious garage restoration of my 1966 911 (#303636). I can not get #4 cylinder to fire. I dumped a small amount of fuel into each throat at about 1500 rpm. Five out of six cylinders struggled and returned to correct idle. Number 4 had no action at all. Spark yes. Fuel yes.
I would like a short list of common sense things to check out. I am sure this is a no brainer for most members here. I need some input.
Skeeters
Logic would suggest that if you pour fuel into the throat of a cylinder and nothing happens - there is no spark? In some cases plugs may fire when grounded to the block out in the open - but still not be able to ignite fuel mix under compression.
Hook a timing light to #4 wire and see if you get a signal. Try a new plug on #4.
Do a quick compression check - gauges are cheap. Pull valvecovers and check valves for correct gap.
At it's most basic core you NEED four things to fire .....Compresion, Air, Fuel and Spark figure out which you don't have and that will send you on the right path.
Internal Combustion engine is very simple machine when broken down to minimum needs.
Good luck
Joe D
1966 911 #302694
If there is too much gas it will not fire. If you then pour more gas onto it, it still will not fire, so your test may indicate that the cylinder is running rich. Also, it takes more energy to light the spark under compression than in the air, so if there is a high resistance fault in the ignition wire for that cylinder, it could be not firing when you think it is. Check for an idle jet not screwed in all the way, and try replacing the plug wire and connector.
SV
I had a similar problem after an engine swap. I had compression, spark, gas and air but it was not firing. I had the ignition cables connected in the wrong sequence. The engine i swapped in was a 79SC on which the distributor turns anticlockwise.
If weber carbs then swap carbs side-to-side to see if problem follows carbs. My guess is blocked fuel gallery feeding idle jet from fuel bowl.
Paul Abbott
Early S Member #18
Weber service specialist
www.PerformanceOriented.com
info@PerformanceOriented.com
530.520.5816
Hi Paul. They are Webers, the same IDT's that you just helped me out on. The engine sounds very different, much stronger other than the #4 SNAFU. I will keep you posted. Dan
I am just going to forget about the #4 cylinder problem for now. Time to finish off the interior and move towards the trunk area.
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