Joined: May 2024 Posts: 13 Threads: 5
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0
Location: Basingstoke
Car type: 1937 Austin 7 special
After many delays i have finally managed to get my special on a road test today but it has a miss fire on number one cylinder. I have taken all the plugs out and 2, 3 , and 4 are sooty as it is running a bit rich but number 1 is wet but no soot however there appears to be a nice healthy spark at the plug . When i touched the exhaust manifold number 1 doesnt appear as hot as 2,3 and 4. I know it will be a process of elimination and any pointers will be most appreciated.
Joined: Aug 2017 Posts: 994 Threads: 22
Reputation:
10
Location: Near Cambridge, UK
Car type: 1928 tourer (mag type), short chassis Gould Ulster
If you have a starting handle check compressions by turning the engine. If number one is low compared with the others check for full valve travel. After an engine has been unused for a substantial time it might have a stuck valve. I have cured this with the valve cover off and a substantial screwdriver poked into the offending spring and pushing it down with the engine running. Probably necessary to hold screwdriver in place while someone else starts the engine.
Joined: May 2024 Posts: 13 Threads: 5
Reputation:
0
Location: Basingstoke
Car type: 1937 Austin 7 special
Thankyou Robert. There is no starting handle. Its a newly rebuilt engine , new pistons ,crank and rods and running an 1 1/4 SU on a log type manifold. It seems to tick over ok and the mis firing occurs once i pull away and under load
Joined: Nov 2017 Posts: 564 Threads: 56
Reputation:
7
Location: West Yorkshire
Car type: Type 65 1934 + RP 1932
If the compression on number 1 is good I would suspect the spark is failing under load. The condenser appears to be working on 2,3 & 4, so I would look for a cracked distributor cap, defective plug lead or spark plug with high resistance.
