Mild street 460 BBC with a 750 Dominator. My buddy takes it to a shop to change intake and install a vacuum secondary 750. It's the exact intake that came off when he put the Dominator on. It ran great when it came off. He goes to the shop to pick up the car and it starts and runs fine. It sits for a week and is very hard to start but runs fine to and from his local cruise in. A month later he can't get it to start and it's been that way for a couple months. It spins but acts like there's no spark. It has an MSD HEI. So my first check is primary voltage and it reads 9.6. I make a jumper wire directly from the battery and I've got 12.4. We try and try and it won't fire. I mark the base of the distributor to the intake and start moving it around. It finally starts and we set the timing at 32 total, which is where it was when it ran great. we let it sit for a while and try to start it again and it just spins.
I'm thinking coil, what do you think?
Anybody have the test ohm numbers to test an MSD coil?

This message has been edited. Last edited by: Ron Gusack,

quote:

Originally posted by Ron Gusack:

Anybody have the test ohm numbers to test an MSD coil?

MSD-8225 coil Primary measures 0.6 ohms . Secondary measures 8900 ohms

Test light to tach terminal and spin it over. If it flashes pickup and module are good. No flash and it's time to go inside. Check the contact in the cap where it touches the rotor. You can actually make them spark a tester by passing a soldering gun close to the coil! If you don't get a flash at the tach terminal when you open it up look at the wires from the pickup to the module. You can unplug the pickup from the module and spin the motor and you should see AC voltage toggling.

Eman told you just about all you need to know.

The only thing I would add is that many times these pickups get corrosion on the terminals, usually the two terminals that go to the pickup coil. Look at all of them, if you see green, it ain't money!

Obviously the distributor got removed and installed again to swap the intake and wires got moved around.

See why you had less than 12 volts going to it in the first place. Lots of older cars had a high resistance wire feeding the +12 volts to the coil instead of using a resistor like Chrysler did. That wire will not supply 12 volts with any load on it.

Thanks for the information. When it warms up some I'll go back and do some testing.

After I pulled my jumper wire off we retested the primary wire and got battery voltage but it didn't have a load on it.

The car has a strange electrical issue because at one point it went totally dead, like the battery was removed from the car. We fooled around with the main disconnect which is on his dash board and power came back. I'm guessing he has a faulty power switch. It's a Jeg's so probably not a high amp switch.

Experienced this on two different vehicles both with the same hei distributor. Base plate of distributor seemed to loose it's ground path through the mounting shaft. Run a ground wire from the mounting screw of the ignition module inside the distributor out to battery ground. Ran my wire out small vent hole in base plate of distributor. Never happened again.

quote:

Originally posted by Ron Gusack:
Thanks for the information. When it warms up some I'll go back and do some testing.

After I pulled my jumper wire off we retested the primary wire and got battery voltage but it didn't have a load on it.

The car has a strange electrical issue because at one point it went totally dead, like the battery was removed from the car. We fooled around with the main disconnect which is on his dash board and power came back. I'm guessing he has a faulty power switch. It's a Jeg's so probably not a high amp switch.

Had a similar issue once, and it was a bad main switch. Didn't do it all the time, which made it a pain to find. Finally had replaced pretty much everything else, so thought wth, and replaced it...no issues after that.

quote:

Originally posted by Maxx Levell:

Had a similar issue once, and it was a bad main switch. Didn't do it all the time, which made it a pain to find. Finally had replaced pretty much everything else, so thought wth, and replaced it...no issues after that.

It's always the last thing you try isn't it? LOL

quote:

Originally posted by CURTIS REED:

quote:

Originally posted by Maxx Levell:

Had a similar issue once, and it was a bad main switch. Didn't do it all the time, which made it a pain to find. Finally had replaced pretty much everything else, so thought wth, and replaced it...no issues after that.

It's always the last thing you try isn't it? LOL

LOL...never had one fail before. Figured if my lights came on after I flipped the switch it was good...apparently that wasn't the case

Pretty sure it was someone on here who suggested replacing it. I didn't honestly think it was going to change anything, but wanted to get one of the newer switches with the lugs for the alternator cable anyway. Once we swapped that little rascal in, no more issues...

I looked at the Jegs switch that he has in the car and it's rated at 20 amps continuous. That seems crazy low to me, especially for a street car. The fuel pump, fans, ignition and headlights probably draw more than 20.

quote:

Originally posted by Ron Gusack:
I looked at the Jegs switch that he has in the car and it's rated at 20 amps continuous. That seems crazy low to me, especially for a street car. The fuel pump, fans, ignition and headlights probably draw more than 20.

Not bashing anyone...but hypothetically, the switch that I had that failed MIGHT have been one of the big speed shops house brand switch ! Replaced with the Moroso unit, and problem solved.

I would recommend using a Cole-Hersee battery disconnect switch. P/N 75903 has 4 poles/2 separate circuits, (One circuit for Batt, one for Alt). Rated 1000 Amps intermittent (for starting), 125 A continuous. Or opt for P/N 75904, which is identical, except the internal terminals are Silver plated, which probably resist oxidation better. And the 75904-01 is even better, weather-proofed with O-rings and gaskets. Common (fair) distributor prices for them are about $50, $57, and $63 for those 3 part numbers.