Have just put the 2 barrel holley back on the motor after a rebuild,and the engine isnt even trying to fire up.Its getting plenty of fuel,have checked the coil(thats good)done the spark plug earthed to the block test and its got a real weak spark.The coil ohm test is at 1.8 ohms which is in the range i think.I am running a mopar electronic ignition with a chrome colour box with ZFR5N plugs at 40 thou and still using a dual ballast resistor as i cant seem to find a 3 ohm coil here in oz to delete the ballast.Any help you guys could give me would be greatly appreciated.

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Another AP5 valiant still going strong.

Timing is off? (check distributor position?)

Checked timing and its still spot on,am only getting 5.5 volts at the coil with the ignition on and 12 when cranking.did the spark plug test earthed to the block and cranked it over to get a real weak spark. Checked the coil and it seems to be right in the ohm range at 1.8.

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Another AP5 valiant still going strong.

Are you at #1 or #6? If you set the sprockets dot to dot, you will be on #6.

Richard

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Part of Tyrde-Browne Racing

If you're timing is right, it could be that your problem is a weak spark. Many things can cause that on both the low and high voltage side.

Let's start with the low voltage side:
When cranking, the ballast ought to be bypassed and you ought to have 12V at the coil(+). If you have a poor connection between the starter relay and the coil, you may not be getting much or any voltage to the coil in START, but be getting normal voltage in RUN. The (-) side goes to the control box, and that must be well grounded to work properly, so check those carefully. To check the (+) coil, have somebody turns the key to START while you measure the (+) coil. Beware that as the field collapses in the coil you can generate enough voltage to hurt yourself or the meter, so disconnect the meter before turning the key away from START. You can disable the starter to prevent cranking while you test the relay by removing the cable from the relay.

If you've got a good 12V at the coil(+), see that coil(-) sits at <0.7V (but not 0.0V) when on, but not firing - that's the switching transistor in the control box. If that's good, it's possible that the control box is bad or there's a problem with the pickup and connections. You can make/break the magnetic flux at the pickup to generate a signal for testing.

I always carry a spark ignition box; I've had the Mopar orange one die w/o warning at 2K miles and now run an old NAPA top-of-the-line box.

Next look at the high voltage side:
Coils don't last forever, and often the insulation inside starts breaking down, resulting in weak or no spark after >100,000 mi. I've seen new coils go bad in funny ways and apparently arc internally, frying the ignition box. Spark plug wires, especially the coil-to-distributor wire, go bad in funny hard-to-pin-down ways; try substituting another coil-to-dist wire and see if the spark improves.

You need a good spark to start a cold engine, so I'd look at that 1st. Good luck!

Turned out it was the second hand holley overfuelling the motor,put the single barrel(second hand too)back on and away she goes.Sofrom now on i'm not playing around with second hand rubbish and buying new for the VAL. Thanks for all your replies.AL.

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Another AP5 valiant still going strong.