Thank you all very much...problem was the coil after all.
On Mar 21, 2010, at 12:28 AM, Barney Gaylord wrote:
> Always do the diagnostic work before throwing money at it.
> Basic stuff first, start here:
> Spark and fuel curcuits: http://mgaguru.com/mgtech/electric/circ_i.htm
> Grab test light. Switch on.
> A3 = light --- If not, fix the fee wire.
> SW = light --- If not, fix the fee wire.
> CB = no light when points closed --- If light, no ground
> through distributor.
> Broken flex wire (2 of them), or loose base clamp.
> CB = light when points are open --- If not, shorting across
> points in distributor.
> Common wiring error, points wire shorted to ground on screw
> Points of course must open and close.
> Use ohm meter.
> Check resistance in coil, SW to CB.
> 3.2 ohms = good
> 1.6 ohms = wrong coil
> 50 mega ohms (open circuit) = bad coil.
> Check resistance, distriutor side terminal to engine block with
> points closed.
> Near 0 ohms is good.
> >1/4 ohm (250 mili ohm or more) = burned points.
> If that checks out, then check for spark at coil HT wire (not plug
> Very weak spark from coil = bad condenser
> No spark out of coil = bad coil
> Spark from coil but no spark at any plugs = bad rotor or broken
> center contact in cap.
> Spark on some plugs, not others = fault of cap or HT wires or plugs.
> Check for spark on each HT wire to engine bolt (not thorugh plugs).
> Some wires no spark, check resistance of wires end to end.
> 0 ohms = solid wire, good
> ~5000 ohms per foot of length = resistor wire, good
> ~50 mega ohms (open circuit) = bad wire or bad end connectors.
> Check resistance of plugs from top connector to center electrode.
> 0 ohms = solid plug, good
> ~3000 ohms, resistor plug, good
> 6,000 ohms or more = resistor plug, faulty
> If that's okay, then spark on some plugs but not others = bad cap.
> Check resistance of each post inside to outside.
> 0 ohms = good post.
> 50 mega ohms = corroded aluminum post
> Repalce cap. Try to buy one with copper posts.
> If posts asre good, visual check inside of cap
> Crack or tracking inside of cap = bad cap.
> If you haven't got it yet, read these pages:
> Coil Testing: http://mgaguru.com/mgtech/ignition/ig108.htm
> Ignition Trouble Shooting: http://mgaguru.com/mgtech/ignition/
> After all of that, call back about either success or failure.
> At 12:58 PM 3/20/2010 -0400, W. David Houser wrote:
>> .... replaced coil, no change. .... switch on, fuel pump works,
>> lights, getting gas...no spark out of coil....
>> Car ran finecoming into garage and then it didn't.
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