78 cobalt ignition issues?

[winterfunguy]

Ok my cobalt is driving me nuts, 3 days ago we launched it and could not get 100 yards from the dock before it started caughing and cutting out badly (no backfiring). I disassembled and cleaned carb (mercarb 4bbl by Carter), replaced fuel water seperator, replaced line from filter to carb, replaced anti-siphon valve @ tank, replaced cap and rotor...didn't help. Replaced points and it ran good for a few hours then started slowly running like crap again. Put a new high energy coil on and no difference. Now it runs pretty good in neutral but in gear it starts missing at about 1000-1100 rpm in gear, I rechecked dwell of points and dwell is 26? and gap is. 018". I pulled ignition wires off 1 at a time and didn't really notice any of the wires causing the engine to miss when removed???? Could this be a faulty shift interior switch? I put a 12v jumper from batt to +post of the coil and no change...I'm at my witts end guys.

 

[winterfunguy]

Re: 78 cobalt ignition issues?

Oh yah, I replaced the condensor and points last year but did not replace condensor this time around.

 

[haulnazz15]

Re: 78 cobalt ignition issues?

First of all what engine are we talking about, and have you verified your timing (both base timing and advance)?

 

[jmorgan87]

Re: 78 cobalt ignition issues?

I suppose faulty it could do anything, but I thought shift interrupt is only done when coming out of gear, going into neutral, and also only when under a load. Otherwise there isn't enough force to engage the interrupt grounding the coil and cutting off spark when running on muffs... again I don't know what a typical faulty interrupt symptoms are though.

When is the last time you replaced the cap? You pulled each plug wire off while the motor was missing, or was not missing? and no change to the engine at all ?

I've done this on cars, but not boats. Run the engine at night/dark, and look for any type of arcing. Plug cap, and wires. maybe a plug wire is breaking down?

 

[winterfunguy]

Re: 78 cobalt ignition issues?

I got it! Two problems caused my issue...first was a bad condensor that got my spark back to normal...the second was a distributor out of phase, a hei distributor gets the rotor phased at 5:30 but points gets phased at 6:30, by rephasing the rotor my engine went from wit @4800rpm to wit at 5200 rpm and this engine became absolutely scarry fast!