Outer Limits 4x4 Board

i have installed a hei distributor in my range rover 3.9 v8 as the old dizzy fell apart so i thought i would be a good time to upgrade .i have 12v at ignition but drops to 10v at crank still no spark .i have tested the coil for resistance and from the batt+ to the rotor out it has a infinite reading so i bought a new coil but the new coil has the same reading .the old coils from the other setup show 9.25 /20k ohms but both the hei coils show nothing . could i have just bad luck and got two brand new dud coils in a row or am i missing something

Is this an external coil or a coil-in-cap type?

I am not sure on the coil-in-cap types, but with an external HEI coil you should be looking for very low resistance (~1 ohm, definitely less than 10 ohms) across the two terminals, and very high resistance (but not infinite) from the coil centre to the ground terminal, even higher than with your ordinary coil.

I recently put an HEI dizzy on my RR 4.2 and I still have the new coil on a bench, I will try to go check the reistances later.

chimpboy wrote:Is this an external coil or a coil-in-cap type?

I am not sure on the coil-in-cap types, but with an external HEI coil you should be looking for very low resistance (~1 ohm, definitely less than 10 ohms) across the two terminals, and very high resistance (but not infinite) from the coil centre to the ground terminal, even higher than with your ordinary coil.

I recently put an HEI dizzy on my RR 4.2 and I still have the new coil on a bench, I will try to go check the reistances later.

Where's the switching element for the coil primary? If it's a transistor performing the switching, and it's built into the coil (is this ever done?) then it probably will be very high resistance when it's "off".

thanks chimp .its a coil in cap dizzy .if anyone could test the resistance from rotor to batt and find a reading it would help

-Scott- wrote:

chimpboy wrote:Is this an external coil or a coil-in-cap type?

I am not sure on the coil-in-cap types, but with an external HEI coil you should be looking for very low resistance (~1 ohm, definitely less than 10 ohms) across the two terminals, and very high resistance (but not infinite) from the coil centre to the ground terminal, even higher than with your ordinary coil.

I recently put an HEI dizzy on my RR 4.2 and I still have the new coil on a bench, I will try to go check the reistances later.

Where's the switching element for the coil primary? If it's a transistor performing the switching, and it's built into the coil (is this ever done?) then it probably will be very high resistance when it's "off".

I do not know about the coil-in-caps, what I have is a dizzy with an ignition module (I assmue this is "a transistor performing the switching" you refer to), and the coil is separate like an old-school non-HEI setup.

I would have guessed that the coil-in-cap types have (a) a coil in the cap and (b) an ignition module on the side of the dizzy but I am not sure.

Defmec where is the gear from, is it buick stuff?

I could be completely talking out my arse here, its a long time since I fiddled with a petrol engine, so flame suit already zipped.

I fitted HEI distributors to a couple of 308s years ago, from memory(hazy) I think I had to remove the coil resistor wire from the original wiring harness.
Some cars have a resistor on the coil, some used to use a predetermined length of 'resistor wire' as part of the wiring harness instead of a resistor at the coil. I think the HEI dizzies need full 12volts??