Hi Guy's,'
I've got a problem : My '29 AA backfires when I want " power " to climb a hill or a bridge, and also backfires when I put the trottle down. I can feel the power dropping away when I push the trottle down. The problem is not always there, sometimes I can do 20 to 30 miles without any problem, and then .. Bang..bang...
When I pull the choke out, I regain power so I suppose it's a fuel problem.
The truck used to give quite a good , smooth and powerfull ride, and now the engine lacks power, and vibrates when over 20 mph.
When someone follows me, they complain about the exhaust smelling like gas.
Any idea, suggestions???? Everything in the carb has been replaced by new stuff, no aditional fuel filters, new shut-off valve, clear fuel lines...
I'm out of clues..
erwin.
Backfire
-
Drew Mashburn
- Posts: 496
- Joined: April 25th, 2005, 2:25 pm
- Model Year: 1930
- Location: Ojai, California
Backfire
Common causes of exhaust backfire after driving for a few miles include, but are not limited to:
Partially blocked fuel line, especially at the tank shut off valve in the tank. There may be gas flow, but not enough when the engine is under load. Make sure the gas cap is vented. Loosen the cap and drive it. If the problem goes away, it is the cap. Remove the fuel shut off valve and verify that there is a full 1/4" pipe thread of fuel flow. If not, clean the hole in the gas tank to remove built up junk around the fuel shut off threads. Check the fuel shut off valve. Those things can clog up. Check the caruretor float level. It may be set too low. Blow out the fuel line with compressed air. Make certain the fuel filter is flowing clear. Copper fuel lines can vapor lock under hot weather conditions. Make sure the fuel line is steel.
The coil can break down under load after it is hot, the condenser can do the same thing, one or more spark plugs can do the same thing, a poor electrical connection under the distributor breaker plate can do the same thing, a bad set of points can also cause it.
Check all the electrical connections. Make sure there is no oxidation on any terminal from the battery to the instrument cluster, to the ignition switch and distribution block to the distributor. Defective ignition switches are sometimes the culprit.
A bad electrical connection from the ignition cable to the distributor can cause the same condition.
Take each item one step at a time and work your way through each item diagnosing each part. Mark each item off as they pass. There is no need to thow parts at your truck. A simple ohm meter available at radio shack or walmart is very valuable diagnosing electrical problems.
Partially blocked fuel line, especially at the tank shut off valve in the tank. There may be gas flow, but not enough when the engine is under load. Make sure the gas cap is vented. Loosen the cap and drive it. If the problem goes away, it is the cap. Remove the fuel shut off valve and verify that there is a full 1/4" pipe thread of fuel flow. If not, clean the hole in the gas tank to remove built up junk around the fuel shut off threads. Check the fuel shut off valve. Those things can clog up. Check the caruretor float level. It may be set too low. Blow out the fuel line with compressed air. Make certain the fuel filter is flowing clear. Copper fuel lines can vapor lock under hot weather conditions. Make sure the fuel line is steel.
The coil can break down under load after it is hot, the condenser can do the same thing, one or more spark plugs can do the same thing, a poor electrical connection under the distributor breaker plate can do the same thing, a bad set of points can also cause it.
Check all the electrical connections. Make sure there is no oxidation on any terminal from the battery to the instrument cluster, to the ignition switch and distribution block to the distributor. Defective ignition switches are sometimes the culprit.
A bad electrical connection from the ignition cable to the distributor can cause the same condition.
Take each item one step at a time and work your way through each item diagnosing each part. Mark each item off as they pass. There is no need to thow parts at your truck. A simple ohm meter available at radio shack or walmart is very valuable diagnosing electrical problems.