My 59 fuelie occasionally backfires when I am out driving it. It seems to happen sometimes when I lift the throttle at medium RPMs. Am I correct in my understanding that unspent fuel is igniting as it is leaving the exhaust? How much of this, if any, is normal and to be expected? Is there some adjustment that should be made to the car's mechanical setup? I have not really driven it in any hot weather yet. I live in Chicago and have only had the car for a couple of months. The previous owner recommended adding a lead-based additive to the fuel when I fill up. It was my understanding that it would be good for the valves, increase the octane, etc. In light of some earlier dicussion from the membership on this board, I might eliminate that procedure in the future. I would also appreciate any general advise on start-up/warm-up procedures (let idle on its own for a few moments, rev it a little bit at higher RPMs to warm up the fluids faster?) Is it any different in colder weather? Thanks.
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Re: C1 engine backfiring
I would start by first checking the ignition timing. At idle it should be around 10 to 12 degrees advanced. If the timing is correct, then check that the choke on the fuel injection is turning off properly. To check this, once the engine warms up the enrichment leaver should move to the lean position. If that is working correctly, check the enrichment leaver moves when you blip the accelerator, it should move from lean to rich. If that works ok then check the mixture using an oxygen sensor exhaust snuffer best done on a dyno.(if you get black smoke during driving, the rich setting may be to rich which could cause it to backfire) You can set the rich and lean settings on the fuel injector. If it still back fires after that, then it may have a valve train problem. I would suggest looking a workshop manual before you adjust the fuel injection. Andrew -
Re: C1 engine backfiring
It sounds like you are experiencing afterfires, not backfires. A backfire is when the engine spits back through the inlet system. Afterfires are popping in the exhaust. They can be caused by a lean idle mixture or a burned valve. A lean mixture may misfire in the cylinder, but ignite when it passes into the hot exhaust system. Similarly, a burned exhaust valve can allow free mixture to escape to the exhaust system where it ignites. The possibility of a burned valve can be confirmed or eliminated with a compression or leak down test.
If the engine will operate detonation free on the highest octane commercial gasoline available to you, there is no need for any additives.
The proper way to warm up any engine is to drive away as soon as the fast idle stabilizes, but drive at a very moderate pace using minimum revs and throttle until the engine warms up, and as the engine warms up with moderate pace driving, so will the transmission and axle.
DukeComment
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Re: C1 engine backfiring
Thanks guys for your helpful input! - KevinComment
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