Spark or Gas? Jr. Tech at work

Mike Rocket J. Squirrel Elliot · 2004-09-21T22:19:14+00:00

Hi all,Cruising down the Coast Highway today to run an errand in the newly-running Wonderbus. At just about the same spot where its previous engine overheated and cracked a valve seat, the Wonderbus started acting erratic, all kind of herky-jerky. At first I thought it was gusts of wind blowing off the ocean, but no: when I reached a sheltered spot I continued to feel it. The engine had gotten spastic, sort of stuttery. Did not have a lot of power, didn't like to rev.Limped to a local restaurant (Miracles Cafe in Solana Beach) and had lunch, letting the engine cool down before poking and probing. While eating I turned over the symptoms in my head, realizing that I don't have nearly enough troubleshooting experience to even begin to guess. Spark or fuel? I knew it was one or the other. After lunch, proceeded to poke and probe as planned, all hose and wiring connections tight. Nothing to go on.Started her up and she was still unhappy. Since Coast Highway is nearly flat, I took it real easy back home. Spark or fuel? I continued to think about it.Once home I unplugged the wiring harness from my timing light and identified the two wires that connect to the plug wire clamp, and connected them to my digital oscilloscope. I ain't got an ignition analyzer but I know a current probe when I see one. Got a real nice display on the 'scope, too. All the plug wires displayed the same waveform, while the coil wire showed four times as many spikes in the same amount of time. But everything was noisy and erratic. When revving the engine there was all kind of rubbish. But what do I know? I never looked at the output of the coil or the individual plug wires before.Spark or fuel? Not enough information to go on. Opening the fuel pump to flush its filter would take a while, since the carb is in the way of reaching one of the four bolts on top with any screwdriver I have. Turned the engine over by hand a couple of time, with the fuel line to the carb disconnected. Fuel pump squooshed...

Sep 21, 2004 20 Replies

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Mike Rocket J. Squirrel Elliot 22 years ago

I'll double-check. I adjusted the new carb per Bentley's but something might have drifted.

Braukuche Dan has a spare stovepipe for the engine that I'll be picking up this weekend. I might be experiencing icing down the old carb. Try a this, try that . . . sooner or later I'll get it sorted out. It's kind of fun, this detective work.

-- Mike "Rocket J Squirrel" Elliott

71 Type 2: the Wonderbus 84 Westphalia: "Mellow Yellow (The Electrical Banana)" KG6RCR

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