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Old 01-21-2015, 09:33 PM
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What is the A4 "distributor pulse sequence"?

I had a good mechanic get my balky A4 running just fine after I had done everything in the book to get it going and failing. He found a bad wire in the ignition system near the coil. Mechanic got his training on hot rod engines.

To celebrate, I had him install a new Seaward instrument panel I bought about 12 years ago before Seaward stopped making them. My old instrument panel did not have a tachometer, but the new one does. The engine still runs perfectly with the new panel. Mechanic says the tach is off, but can be adjusted if I can get the "distributor pulse sequence" for the A4 distributor. It's not in the overhaul manual. He says he can adjust the tach if he knows this. Does anyone have this information? I have never heard of it.

S/V Catmandu
1982 Catalina 27 tall rig
A4 late model
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Old 01-21-2015, 10:26 PM
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ndutton ndutton is offline
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Interesting question.

The only adjustment I'm aware of with distributor driven tachometers is a selector switch to choose either 4, 6 or 8 cylinders. Once the selection is made, that's it. It tells the tachometer how many distributor pulses = one crankshaft rotation (for technical accuracy, it's the switch setting ÷2).

Alternator driven tachometers, typical on diesels, have an adjustment screw to dial in the correct reading in consideration of the crank/alternator pulley ratio. To do this you'll need an external tachometer instrument (we like the optical no-contact tach from Harbor Freight Tools) to measure the RPM and set the boat's tachometer to match. This can be used to check a distributor driven tach as well.

If you'd rather not purchase the optical tool I'd be happy to loan you mine.
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others

Last edited by ndutton; 01-21-2015 at 10:28 PM.
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distributor, tachometer

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